Add and use more static symbols.

Note that the output of `unpretty-debug.stdout` has changed. In that
test the hash values are normalized from a symbol numbers to small
numbers like "0#0" and "0#1". The increase in the number of static
symbols must have caused the original numbers to contain more digits,
resulting in different pretty-printing prior to normalization.

src/librustc_ast/expand/allocator.rs

@@ -9,7 +9,7 @@ pub enum AllocatorKind {
 }
 
 impl AllocatorKind {
-    pub fn fn_name(&self, base: &str) -> String {
+    pub fn fn_name(&self, base: Symbol) -> String {
         match *self {
             AllocatorKind::Global => format!("__rg_{}", base),
             AllocatorKind::Default => format!("__rdl_{}", base),
@@ -26,29 +26,29 @@ pub enum AllocatorTy {
 }
 
 pub struct AllocatorMethod {
-    pub name: &'static str,
+    pub name: Symbol,
     pub inputs: &'static [AllocatorTy],
     pub output: AllocatorTy,
 }
 
 pub static ALLOCATOR_METHODS: &[AllocatorMethod] = &[
     AllocatorMethod {
-        name: "alloc",
+        name: sym::alloc,
         inputs: &[AllocatorTy::Layout],
         output: AllocatorTy::ResultPtr,
     },
     AllocatorMethod {
-        name: "dealloc",
+        name: sym::dealloc,
         inputs: &[AllocatorTy::Ptr, AllocatorTy::Layout],
         output: AllocatorTy::Unit,
     },
     AllocatorMethod {
-        name: "realloc",
+        name: sym::realloc,
         inputs: &[AllocatorTy::Ptr, AllocatorTy::Layout, AllocatorTy::Usize],
         output: AllocatorTy::ResultPtr,
     },
     AllocatorMethod {
-        name: "alloc_zeroed",
+        name: sym::alloc_zeroed,
         inputs: &[AllocatorTy::Layout],
         output: AllocatorTy::ResultPtr,
     },
@@ -70,7 +70,7 @@ pub fn global_allocator_spans(krate: &ast::Crate) -> Vec<Span> {
         }
     }
 
-    let name = Symbol::intern(&AllocatorKind::Global.fn_name("alloc"));
+    let name = Symbol::intern(&AllocatorKind::Global.fn_name(sym::alloc));
     let mut f = Finder { name, spans: Vec::new() };
     visit::walk_crate(&mut f, krate);
     f.spans

src/librustc_attr/builtin.rs

@@ -1041,10 +1041,10 @@ pub fn find_transparency(
                 break;
             } else if let Some(value) = attr.value_str() {
                 transparency = Some((
-                    match &*value.as_str() {
-                        "transparent" => Transparency::Transparent,
-                        "semitransparent" => Transparency::SemiTransparent,
-                        "opaque" => Transparency::Opaque,
+                    match value {
+                        sym::transparent => Transparency::Transparent,
+                        sym::semitransparent => Transparency::SemiTransparent,
+                        sym::opaque => Transparency::Opaque,
                         _ => {
                             error = Some(TransparencyError::UnknownTransparency(value, attr.span));
                             continue;

src/librustc_builtin_macros/deriving/clone.rs

@@ -84,7 +84,7 @@ pub fn expand_deriving_clone(
         is_unsafe: false,
         supports_unions: true,
         methods: vec![MethodDef {
-            name: "clone",
+            name: sym::clone,
             generics: LifetimeBounds::empty(),
             explicit_self: borrowed_explicit_self(),
             args: Vec::new(),

src/librustc_builtin_macros/deriving/cmp/eq.rs

@@ -28,7 +28,7 @@ pub fn expand_deriving_eq(
         is_unsafe: false,
         supports_unions: true,
         methods: vec![MethodDef {
-            name: "assert_receiver_is_total_eq",
+            name: sym::assert_receiver_is_total_eq,
             generics: LifetimeBounds::empty(),
             explicit_self: borrowed_explicit_self(),
             args: vec![],

src/librustc_builtin_macros/deriving/cmp/ord.rs

@@ -26,7 +26,7 @@ pub fn expand_deriving_ord(
         is_unsafe: false,
         supports_unions: false,
         methods: vec![MethodDef {
-            name: "cmp",
+            name: sym::cmp,
             generics: LifetimeBounds::empty(),
             explicit_self: borrowed_explicit_self(),
             args: vec![(borrowed_self(), "other")],

src/librustc_builtin_macros/deriving/cmp/partial_eq.rs

@@ -92,9 +92,9 @@ pub fn expand_deriving_partial_eq(
     // avoid defining `ne` if we can
     // c-like enums, enums without any fields and structs without fields
     // can safely define only `eq`.
-    let mut methods = vec![md!("eq", cs_eq)];
+    let mut methods = vec![md!(sym::eq, cs_eq)];
     if !is_type_without_fields(item) {
-        methods.push(md!("ne", cs_ne));
+        methods.push(md!(sym::ne, cs_ne));
     }
 
     let trait_def = TraitDef {

src/librustc_builtin_macros/deriving/cmp/partial_ord.rs

@@ -49,7 +49,7 @@ pub fn expand_deriving_partial_ord(
     let attrs = vec![cx.attribute(inline)];
 
     let partial_cmp_def = MethodDef {
-        name: "partial_cmp",
+        name: sym::partial_cmp,
         generics: LifetimeBounds::empty(),
         explicit_self: borrowed_explicit_self(),
         args: vec![(borrowed_self(), "other")],
@@ -70,10 +70,10 @@ pub fn expand_deriving_partial_ord(
     } else {
         vec![
             partial_cmp_def,
-            md!("lt", true, false),
-            md!("le", true, true),
-            md!("gt", false, false),
-            md!("ge", false, true),
+            md!(sym::lt, true, false),
+            md!(sym::le, true, true),
+            md!(sym::gt, false, false),
+            md!(sym::ge, false, true),
         ]
     };
 
@@ -108,14 +108,14 @@ pub fn some_ordering_collapsed(
 ) -> P<ast::Expr> {
     let lft = cx.expr_ident(span, self_arg_tags[0]);
     let rgt = cx.expr_addr_of(span, cx.expr_ident(span, self_arg_tags[1]));
-    let op_str = match op {
-        PartialCmpOp => "partial_cmp",
-        LtOp => "lt",
-        LeOp => "le",
-        GtOp => "gt",
-        GeOp => "ge",
+    let op_sym = match op {
+        PartialCmpOp => sym::partial_cmp,
+        LtOp => sym::lt,
+        LeOp => sym::le,
+        GtOp => sym::gt,
+        GeOp => sym::ge,
     };
-    cx.expr_method_call(span, lft, cx.ident_of(op_str, span), vec![rgt])
+    cx.expr_method_call(span, lft, Ident::new(op_sym, span), vec![rgt])
 }
 
 pub fn cs_partial_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> P<Expr> {

src/librustc_builtin_macros/deriving/debug.rs

@@ -29,7 +29,7 @@ pub fn expand_deriving_debug(
         is_unsafe: false,
         supports_unions: false,
         methods: vec![MethodDef {
-            name: "fmt",
+            name: sym::fmt,
             generics: LifetimeBounds::empty(),
             explicit_self: borrowed_explicit_self(),
             args: vec![(fmtr, "f")],

src/librustc_builtin_macros/deriving/decodable.rs

@@ -8,7 +8,7 @@ use rustc_ast::ast;
 use rustc_ast::ast::{Expr, MetaItem, Mutability};
 use rustc_ast::ptr::P;
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::symbol::Symbol;
+use rustc_span::symbol::{sym, Symbol};
 use rustc_span::Span;
 
 pub fn expand_deriving_rustc_decodable(
@@ -30,7 +30,7 @@ pub fn expand_deriving_rustc_decodable(
         is_unsafe: false,
         supports_unions: false,
         methods: vec![MethodDef {
-            name: "decode",
+            name: sym::decode,
             generics: LifetimeBounds {
                 lifetimes: Vec::new(),
                 bounds: vec![(

src/librustc_builtin_macros/deriving/default.rs

@@ -27,7 +27,7 @@ pub fn expand_deriving_default(
         is_unsafe: false,
         supports_unions: false,
         methods: vec![MethodDef {
-            name: "default",
+            name: kw::Default,
             generics: LifetimeBounds::empty(),
             explicit_self: None,
             args: Vec::new(),

src/librustc_builtin_macros/deriving/encodable.rs

@@ -92,7 +92,7 @@ use crate::deriving::pathvec_std;
 use rustc_ast::ast::{Expr, ExprKind, MetaItem, Mutability};
 use rustc_ast::ptr::P;
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::symbol::Symbol;
+use rustc_span::symbol::{sym, Symbol};
 use rustc_span::Span;
 
 pub fn expand_deriving_rustc_encodable(
@@ -114,7 +114,7 @@ pub fn expand_deriving_rustc_encodable(
         is_unsafe: false,
         supports_unions: false,
         methods: vec![MethodDef {
-            name: "encode",
+            name: sym::encode,
             generics: LifetimeBounds {
                 lifetimes: Vec::new(),
                 bounds: vec![(

src/librustc_builtin_macros/deriving/generic/mod.rs

@@ -226,7 +226,7 @@ pub struct TraitDef<'a> {
 
 pub struct MethodDef<'a> {
     /// name of the method
-    pub name: &'a str,
+    pub name: Symbol,
     /// List of generics, e.g., `R: rand::Rng`
     pub generics: LifetimeBounds<'a>,
 
@@ -681,7 +681,7 @@ impl<'a> TraitDef<'a> {
         let opt_trait_ref = Some(trait_ref);
         let unused_qual = {
             let word = rustc_ast::attr::mk_nested_word_item(Ident::new(
-                Symbol::intern("unused_qualifications"),
+                sym::unused_qualifications,
                 self.span,
             ));
             let list = rustc_ast::attr::mk_list_item(Ident::new(sym::allow, self.span), vec![word]);
@@ -818,7 +818,7 @@ impl<'a> MethodDef<'a> {
     ) -> P<Expr> {
         let substructure = Substructure {
             type_ident,
-            method_ident: cx.ident_of(self.name, trait_.span),
+            method_ident: Ident::new(self.name, trait_.span),
             self_args,
             nonself_args,
             fields,
@@ -913,7 +913,7 @@ impl<'a> MethodDef<'a> {
 
         let ret_type = self.get_ret_ty(cx, trait_, generics, type_ident);
 
-        let method_ident = cx.ident_of(self.name, trait_.span);
+        let method_ident = Ident::new(self.name, trait_.span);
         let fn_decl = cx.fn_decl(args, ast::FnRetTy::Ty(ret_type));
         let body_block = cx.block_expr(body);
 
@@ -1315,7 +1315,7 @@ impl<'a> MethodDef<'a> {
                 // Since we know that all the arguments will match if we reach
                 // the match expression we add the unreachable intrinsics as the
                 // result of the catch all which should help llvm in optimizing it
-                Some(deriving::call_intrinsic(cx, sp, "unreachable", vec![]))
+                Some(deriving::call_intrinsic(cx, sp, sym::unreachable, vec![]))
             }
             _ => None,
         };
@@ -1363,7 +1363,7 @@ impl<'a> MethodDef<'a> {
             for (&ident, self_arg) in vi_idents.iter().zip(&self_args) {
                 let self_addr = cx.expr_addr_of(sp, self_arg.clone());
                 let variant_value =
-                    deriving::call_intrinsic(cx, sp, "discriminant_value", vec![self_addr]);
+                    deriving::call_intrinsic(cx, sp, sym::discriminant_value, vec![self_addr]);
                 let let_stmt = cx.stmt_let(sp, false, ident, variant_value);
                 index_let_stmts.push(let_stmt);
 
@@ -1464,7 +1464,7 @@ impl<'a> MethodDef<'a> {
             // derive Debug on such a type could here generate code
             // that needs the feature gate enabled.)
 
-            deriving::call_intrinsic(cx, sp, "unreachable", vec![])
+            deriving::call_intrinsic(cx, sp, sym::unreachable, vec![])
         } else {
             // Final wrinkle: the self_args are expressions that deref
             // down to desired places, but we cannot actually deref

src/librustc_builtin_macros/deriving/hash.rs

@@ -29,7 +29,7 @@ pub fn expand_deriving_hash(
         is_unsafe: false,
         supports_unions: false,
         methods: vec![MethodDef {
-            name: "hash",
+            name: sym::hash,
             generics: LifetimeBounds {
                 lifetimes: Vec::new(),
                 bounds: vec![(typaram, vec![path_std!(cx, hash::Hasher)])],
@@ -73,7 +73,7 @@ fn hash_substructure(cx: &mut ExtCtxt<'_>, trait_span: Span, substr: &Substructu
             let variant_value = deriving::call_intrinsic(
                 cx,
                 trait_span,
-                "discriminant_value",
+                sym::discriminant_value,
                 vec![cx.expr_self(trait_span)],
             );
 

src/librustc_builtin_macros/deriving/mod.rs

@@ -62,11 +62,11 @@ impl MultiItemModifier for BuiltinDerive {
 fn call_intrinsic(
     cx: &ExtCtxt<'_>,
     span: Span,
-    intrinsic: &str,
+    intrinsic: Symbol,
     args: Vec<P<ast::Expr>>,
 ) -> P<ast::Expr> {
     let span = cx.with_def_site_ctxt(span);
-    let path = cx.std_path(&[sym::intrinsics, Symbol::intern(intrinsic)]);
+    let path = cx.std_path(&[sym::intrinsics, intrinsic]);
     let call = cx.expr_call_global(span, path, args);
 
     cx.expr_block(P(ast::Block {

src/librustc_builtin_macros/global_allocator.rs

@@ -79,12 +79,8 @@ impl AllocFnFactory<'_, '_> {
         self.cx.stmt_item(self.span, item)
     }
 
-    fn call_allocator(&self, method: &str, mut args: Vec<P<Expr>>) -> P<Expr> {
-        let method = self.cx.std_path(&[
-            Symbol::intern("alloc"),
-            Symbol::intern("GlobalAlloc"),
-            Symbol::intern(method),
-        ]);
+    fn call_allocator(&self, method: Symbol, mut args: Vec<P<Expr>>) -> P<Expr> {
+        let method = self.cx.std_path(&[sym::alloc, sym::GlobalAlloc, method]);
         let method = self.cx.expr_path(self.cx.path(self.span, method));
         let allocator = self.cx.path_ident(self.span, self.global);
         let allocator = self.cx.expr_path(allocator);
@@ -115,11 +111,8 @@ impl AllocFnFactory<'_, '_> {
                 args.push(self.cx.param(self.span, size, ty_usize.clone()));
                 args.push(self.cx.param(self.span, align, ty_usize));
 
-                let layout_new = self.cx.std_path(&[
-                    Symbol::intern("alloc"),
-                    Symbol::intern("Layout"),
-                    Symbol::intern("from_size_align_unchecked"),
-                ]);
+                let layout_new =
+                    self.cx.std_path(&[sym::alloc, sym::Layout, sym::from_size_align_unchecked]);
                 let layout_new = self.cx.expr_path(self.cx.path(self.span, layout_new));
                 let size = self.cx.expr_ident(self.span, size);
                 let align = self.cx.expr_ident(self.span, align);

src/librustc_builtin_macros/test_harness.rs

@@ -164,10 +164,8 @@ impl MutVisitor for EntryPointCleaner {
             EntryPointType::MainNamed | EntryPointType::MainAttr | EntryPointType::Start => item
                 .map(|ast::Item { id, ident, attrs, kind, vis, span, tokens }| {
                     let allow_ident = Ident::new(sym::allow, self.def_site);
-                    let dc_nested = attr::mk_nested_word_item(Ident::from_str_and_span(
-                        "dead_code",
-                        self.def_site,
-                    ));
+                    let dc_nested =
+                        attr::mk_nested_word_item(Ident::new(sym::dead_code, self.def_site));
                     let allow_dead_code_item = attr::mk_list_item(allow_ident, vec![dc_nested]);
                     let allow_dead_code = attr::mk_attr_outer(allow_dead_code_item);
                     let attrs = attrs

src/librustc_codegen_llvm/intrinsic.rs

@@ -25,59 +25,59 @@ use rustc_middle::mir::Operand;
 use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt};
 use rustc_middle::ty::{self, Ty};
 use rustc_middle::{bug, span_bug};
-use rustc_span::Span;
+use rustc_span::{sym, symbol::kw, Span, Symbol};
 use rustc_target::abi::{self, HasDataLayout, LayoutOf, Primitive};
 use rustc_target::spec::PanicStrategy;
 
 use std::cmp::Ordering;
 use std::iter;
 
-fn get_simple_intrinsic(cx: &CodegenCx<'ll, '_>, name: &str) -> Option<&'ll Value> {
+fn get_simple_intrinsic(cx: &CodegenCx<'ll, '_>, name: Symbol) -> Option<&'ll Value> {
     let llvm_name = match name {
-        "sqrtf32" => "llvm.sqrt.f32",
-        "sqrtf64" => "llvm.sqrt.f64",
-        "powif32" => "llvm.powi.f32",
-        "powif64" => "llvm.powi.f64",
-        "sinf32" => "llvm.sin.f32",
-        "sinf64" => "llvm.sin.f64",
-        "cosf32" => "llvm.cos.f32",
-        "cosf64" => "llvm.cos.f64",
-        "powf32" => "llvm.pow.f32",
-        "powf64" => "llvm.pow.f64",
-        "expf32" => "llvm.exp.f32",
-        "expf64" => "llvm.exp.f64",
-        "exp2f32" => "llvm.exp2.f32",
-        "exp2f64" => "llvm.exp2.f64",
-        "logf32" => "llvm.log.f32",
-        "logf64" => "llvm.log.f64",
-        "log10f32" => "llvm.log10.f32",
-        "log10f64" => "llvm.log10.f64",
-        "log2f32" => "llvm.log2.f32",
-        "log2f64" => "llvm.log2.f64",
-        "fmaf32" => "llvm.fma.f32",
-        "fmaf64" => "llvm.fma.f64",
-        "fabsf32" => "llvm.fabs.f32",
-        "fabsf64" => "llvm.fabs.f64",
-        "minnumf32" => "llvm.minnum.f32",
-        "minnumf64" => "llvm.minnum.f64",
-        "maxnumf32" => "llvm.maxnum.f32",
-        "maxnumf64" => "llvm.maxnum.f64",
-        "copysignf32" => "llvm.copysign.f32",
-        "copysignf64" => "llvm.copysign.f64",
-        "floorf32" => "llvm.floor.f32",
-        "floorf64" => "llvm.floor.f64",
-        "ceilf32" => "llvm.ceil.f32",
-        "ceilf64" => "llvm.ceil.f64",
-        "truncf32" => "llvm.trunc.f32",
-        "truncf64" => "llvm.trunc.f64",
-        "rintf32" => "llvm.rint.f32",
-        "rintf64" => "llvm.rint.f64",
-        "nearbyintf32" => "llvm.nearbyint.f32",
-        "nearbyintf64" => "llvm.nearbyint.f64",
-        "roundf32" => "llvm.round.f32",
-        "roundf64" => "llvm.round.f64",
-        "assume" => "llvm.assume",
-        "abort" => "llvm.trap",
+        sym::sqrtf32 => "llvm.sqrt.f32",
+        sym::sqrtf64 => "llvm.sqrt.f64",
+        sym::powif32 => "llvm.powi.f32",
+        sym::powif64 => "llvm.powi.f64",
+        sym::sinf32 => "llvm.sin.f32",
+        sym::sinf64 => "llvm.sin.f64",
+        sym::cosf32 => "llvm.cos.f32",
+        sym::cosf64 => "llvm.cos.f64",
+        sym::powf32 => "llvm.pow.f32",
+        sym::powf64 => "llvm.pow.f64",
+        sym::expf32 => "llvm.exp.f32",
+        sym::expf64 => "llvm.exp.f64",
+        sym::exp2f32 => "llvm.exp2.f32",
+        sym::exp2f64 => "llvm.exp2.f64",
+        sym::logf32 => "llvm.log.f32",
+        sym::logf64 => "llvm.log.f64",
+        sym::log10f32 => "llvm.log10.f32",
+        sym::log10f64 => "llvm.log10.f64",
+        sym::log2f32 => "llvm.log2.f32",
+        sym::log2f64 => "llvm.log2.f64",
+        sym::fmaf32 => "llvm.fma.f32",
+        sym::fmaf64 => "llvm.fma.f64",
+        sym::fabsf32 => "llvm.fabs.f32",
+        sym::fabsf64 => "llvm.fabs.f64",
+        sym::minnumf32 => "llvm.minnum.f32",
+        sym::minnumf64 => "llvm.minnum.f64",
+        sym::maxnumf32 => "llvm.maxnum.f32",
+        sym::maxnumf64 => "llvm.maxnum.f64",
+        sym::copysignf32 => "llvm.copysign.f32",
+        sym::copysignf64 => "llvm.copysign.f64",
+        sym::floorf32 => "llvm.floor.f32",
+        sym::floorf64 => "llvm.floor.f64",
+        sym::ceilf32 => "llvm.ceil.f32",
+        sym::ceilf64 => "llvm.ceil.f64",
+        sym::truncf32 => "llvm.trunc.f32",
+        sym::truncf64 => "llvm.trunc.f64",
+        sym::rintf32 => "llvm.rint.f32",
+        sym::rintf64 => "llvm.rint.f64",
+        sym::nearbyintf32 => "llvm.nearbyint.f32",
+        sym::nearbyintf64 => "llvm.nearbyint.f64",
+        sym::roundf32 => "llvm.round.f32",
+        sym::roundf64 => "llvm.round.f64",
+        sym::assume => "llvm.assume",
+        sym::abort => "llvm.trap",
         _ => return None,
     };
     Some(cx.get_intrinsic(&llvm_name))
@@ -86,12 +86,12 @@ fn get_simple_intrinsic(cx: &CodegenCx<'ll, '_>, name: &str) -> Option<&'ll Valu
 impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
     fn is_codegen_intrinsic(
         &mut self,
-        intrinsic: &str,
+        intrinsic: Symbol,
         args: &Vec<Operand<'tcx>>,
         caller_instance: ty::Instance<'tcx>,
     ) -> bool {
         match intrinsic {
-            "count_code_region" => {
+            sym::count_code_region => {
                 use coverage::count_code_region_args::*;
                 self.add_counter_region(
                     caller_instance,
@@ -101,13 +101,13 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 );
                 true // Also inject the counter increment in the backend
             }
-            "coverage_counter_add" | "coverage_counter_subtract" => {
+            sym::coverage_counter_add | sym::coverage_counter_subtract => {
                 use coverage::coverage_counter_expression_args::*;
                 self.add_counter_expression_region(
                     caller_instance,
                     op_to_u32(&args[COUNTER_EXPRESSION_INDEX]),
                     op_to_u32(&args[LEFT_INDEX]),
-                    if intrinsic == "coverage_counter_add" {
+                    if intrinsic == sym::coverage_counter_add {
                         CounterOp::Add
                     } else {
                         CounterOp::Subtract
@@ -118,7 +118,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 );
                 false // Does not inject backend code
             }
-            "coverage_unreachable" => {
+            sym::coverage_unreachable => {
                 use coverage::coverage_unreachable_args::*;
                 self.add_unreachable_region(
                     caller_instance,
@@ -152,7 +152,8 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
         let sig = tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &sig);
         let arg_tys = sig.inputs();
         let ret_ty = sig.output();
-        let name = &*tcx.item_name(def_id).as_str();
+        let name = tcx.item_name(def_id);
+        let name_str = &*name.as_str();
 
         let llret_ty = self.layout_of(ret_ty).llvm_type(self);
         let result = PlaceRef::new_sized(llresult, fn_abi.ret.layout);
@@ -164,18 +165,18 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 &args.iter().map(|arg| arg.immediate()).collect::<Vec<_>>(),
                 None,
             ),
-            "unreachable" => {
+            sym::unreachable => {
                 return;
             }
-            "likely" => {
+            sym::likely => {
                 let expect = self.get_intrinsic(&("llvm.expect.i1"));
                 self.call(expect, &[args[0].immediate(), self.const_bool(true)], None)
             }
-            "unlikely" => {
+            sym::unlikely => {
                 let expect = self.get_intrinsic(&("llvm.expect.i1"));
                 self.call(expect, &[args[0].immediate(), self.const_bool(false)], None)
             }
-            "try" => {
+            kw::Try => {
                 try_intrinsic(
                     self,
                     args[0].immediate(),
@@ -185,11 +186,11 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 );
                 return;
             }
-            "breakpoint" => {
+            sym::breakpoint => {
                 let llfn = self.get_intrinsic(&("llvm.debugtrap"));
                 self.call(llfn, &[], None)
             }
-            "count_code_region" => {
+            sym::count_code_region => {
                 // FIXME(richkadel): The current implementation assumes the MIR for the given
                 // caller_instance represents a single function. Validate and/or correct if inlining
                 // and/or monomorphization invalidates these assumptions.
@@ -206,13 +207,13 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 );
                 self.instrprof_increment(mangled_fn_name, hash, num_counters, index)
             }
-            "va_start" => self.va_start(args[0].immediate()),
-            "va_end" => self.va_end(args[0].immediate()),
-            "va_copy" => {
+            sym::va_start => self.va_start(args[0].immediate()),
+            sym::va_end => self.va_end(args[0].immediate()),
+            sym::va_copy => {
                 let intrinsic = self.cx().get_intrinsic(&("llvm.va_copy"));
                 self.call(intrinsic, &[args[0].immediate(), args[1].immediate()], None)
             }
-            "va_arg" => {
+            sym::va_arg => {
                 match fn_abi.ret.layout.abi {
                     abi::Abi::Scalar(ref scalar) => {
                         match scalar.value {
@@ -238,7 +239,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                     _ => bug!("the va_arg intrinsic does not work with non-scalar types"),
                 }
             }
-            "size_of_val" => {
+            sym::size_of_val => {
                 let tp_ty = substs.type_at(0);
                 if let OperandValue::Pair(_, meta) = args[0].val {
                     let (llsize, _) = glue::size_and_align_of_dst(self, tp_ty, Some(meta));
@@ -247,7 +248,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                     self.const_usize(self.size_of(tp_ty).bytes())
                 }
             }
-            "min_align_of_val" => {
+            sym::min_align_of_val => {
                 let tp_ty = substs.type_at(0);
                 if let OperandValue::Pair(_, meta) = args[0].val {
                     let (_, llalign) = glue::size_and_align_of_dst(self, tp_ty, Some(meta));
@@ -256,8 +257,13 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                     self.const_usize(self.align_of(tp_ty).bytes())
                 }
             }
-            "size_of" | "pref_align_of" | "min_align_of" | "needs_drop" | "type_id"
-            | "type_name" | "variant_count" => {
+            sym::size_of
+            | sym::pref_align_of
+            | sym::min_align_of
+            | sym::needs_drop
+            | sym::type_id
+            | sym::type_name
+            | sym::variant_count => {
                 let value = self
                     .tcx
                     .const_eval_instance(ty::ParamEnv::reveal_all(), instance, None)
@@ -265,21 +271,21 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 OperandRef::from_const(self, value, ret_ty).immediate_or_packed_pair(self)
             }
             // Effectively no-op
-            "forget" => {
+            sym::forget => {
                 return;
             }
-            "offset" => {
+            sym::offset => {
                 let ptr = args[0].immediate();
                 let offset = args[1].immediate();
                 self.inbounds_gep(ptr, &[offset])
             }
-            "arith_offset" => {
+            sym::arith_offset => {
                 let ptr = args[0].immediate();
                 let offset = args[1].immediate();
                 self.gep(ptr, &[offset])
             }
 
-            "copy_nonoverlapping" => {
+            sym::copy_nonoverlapping => {
                 copy_intrinsic(
                     self,
                     false,
@@ -291,7 +297,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 );
                 return;
             }
-            "copy" => {
+            sym::copy => {
                 copy_intrinsic(
                     self,
                     true,
@@ -303,7 +309,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 );
                 return;
             }
-            "write_bytes" => {
+            sym::write_bytes => {
                 memset_intrinsic(
                     self,
                     false,
@@ -315,7 +321,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 return;
             }
 
-            "volatile_copy_nonoverlapping_memory" => {
+            sym::volatile_copy_nonoverlapping_memory => {
                 copy_intrinsic(
                     self,
                     false,
@@ -327,7 +333,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 );
                 return;
             }
-            "volatile_copy_memory" => {
+            sym::volatile_copy_memory => {
                 copy_intrinsic(
                     self,
                     true,
@@ -339,7 +345,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 );
                 return;
             }
-            "volatile_set_memory" => {
+            sym::volatile_set_memory => {
                 memset_intrinsic(
                     self,
                     true,
@@ -350,14 +356,14 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 );
                 return;
             }
-            "volatile_load" | "unaligned_volatile_load" => {
+            sym::volatile_load | sym::unaligned_volatile_load => {
                 let tp_ty = substs.type_at(0);
                 let mut ptr = args[0].immediate();
                 if let PassMode::Cast(ty) = fn_abi.ret.mode {
                     ptr = self.pointercast(ptr, self.type_ptr_to(ty.llvm_type(self)));
                 }
                 let load = self.volatile_load(ptr);
-                let align = if name == "unaligned_volatile_load" {
+                let align = if name == sym::unaligned_volatile_load {
                     1
                 } else {
                     self.align_of(tp_ty).bytes() as u32
@@ -367,26 +373,26 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 }
                 to_immediate(self, load, self.layout_of(tp_ty))
             }
-            "volatile_store" => {
+            sym::volatile_store => {
                 let dst = args[0].deref(self.cx());
                 args[1].val.volatile_store(self, dst);
                 return;
             }
-            "unaligned_volatile_store" => {
+            sym::unaligned_volatile_store => {
                 let dst = args[0].deref(self.cx());
                 args[1].val.unaligned_volatile_store(self, dst);
                 return;
             }
-            "prefetch_read_data"
-            | "prefetch_write_data"
-            | "prefetch_read_instruction"
-            | "prefetch_write_instruction" => {
+            sym::prefetch_read_data
+            | sym::prefetch_write_data
+            | sym::prefetch_read_instruction
+            | sym::prefetch_write_instruction => {
                 let expect = self.get_intrinsic(&("llvm.prefetch"));
                 let (rw, cache_type) = match name {
-                    "prefetch_read_data" => (0, 1),
-                    "prefetch_write_data" => (1, 1),
-                    "prefetch_read_instruction" => (0, 0),
-                    "prefetch_write_instruction" => (1, 0),
+                    sym::prefetch_read_data => (0, 1),
+                    sym::prefetch_write_data => (1, 1),
+                    sym::prefetch_read_instruction => (0, 0),
+                    sym::prefetch_write_instruction => (1, 0),
                     _ => bug!(),
                 };
                 self.call(
@@ -400,32 +406,51 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                     None,
                 )
             }
-            "ctlz" | "ctlz_nonzero" | "cttz" | "cttz_nonzero" | "ctpop" | "bswap"
-            | "bitreverse" | "add_with_overflow" | "sub_with_overflow" | "mul_with_overflow"
-            | "wrapping_add" | "wrapping_sub" | "wrapping_mul" | "unchecked_div"
-            | "unchecked_rem" | "unchecked_shl" | "unchecked_shr" | "unchecked_add"
-            | "unchecked_sub" | "unchecked_mul" | "exact_div" | "rotate_left" | "rotate_right"
-            | "saturating_add" | "saturating_sub" => {
+            sym::ctlz
+            | sym::ctlz_nonzero
+            | sym::cttz
+            | sym::cttz_nonzero
+            | sym::ctpop
+            | sym::bswap
+            | sym::bitreverse
+            | sym::add_with_overflow
+            | sym::sub_with_overflow
+            | sym::mul_with_overflow
+            | sym::wrapping_add
+            | sym::wrapping_sub
+            | sym::wrapping_mul
+            | sym::unchecked_div
+            | sym::unchecked_rem
+            | sym::unchecked_shl
+            | sym::unchecked_shr
+            | sym::unchecked_add
+            | sym::unchecked_sub
+            | sym::unchecked_mul
+            | sym::exact_div
+            | sym::rotate_left
+            | sym::rotate_right
+            | sym::saturating_add
+            | sym::saturating_sub => {
                 let ty = arg_tys[0];
                 match int_type_width_signed(ty, self) {
                     Some((width, signed)) => match name {
-                        "ctlz" | "cttz" => {
+                        sym::ctlz | sym::cttz => {
                             let y = self.const_bool(false);
                             let llfn = self.get_intrinsic(&format!("llvm.{}.i{}", name, width));
                             self.call(llfn, &[args[0].immediate(), y], None)
                         }
-                        "ctlz_nonzero" | "cttz_nonzero" => {
+                        sym::ctlz_nonzero | sym::cttz_nonzero => {
                             let y = self.const_bool(true);
-                            let llvm_name = &format!("llvm.{}.i{}", &name[..4], width);
+                            let llvm_name = &format!("llvm.{}.i{}", &name_str[..4], width);
                             let llfn = self.get_intrinsic(llvm_name);
                             self.call(llfn, &[args[0].immediate(), y], None)
                         }
-                        "ctpop" => self.call(
+                        sym::ctpop => self.call(
                             self.get_intrinsic(&format!("llvm.ctpop.i{}", width)),
                             &[args[0].immediate()],
                             None,
                         ),
-                        "bswap" => {
+                        sym::bswap => {
                             if width == 8 {
                                 args[0].immediate() // byte swap a u8/i8 is just a no-op
                             } else {
@@ -436,16 +461,18 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                                 )
                             }
                         }
-                        "bitreverse" => self.call(
+                        sym::bitreverse => self.call(
                             self.get_intrinsic(&format!("llvm.bitreverse.i{}", width)),
                             &[args[0].immediate()],
                             None,
                         ),
-                        "add_with_overflow" | "sub_with_overflow" | "mul_with_overflow" => {
+                        sym::add_with_overflow
+                        | sym::sub_with_overflow
+                        | sym::mul_with_overflow => {
                             let intrinsic = format!(
                                 "llvm.{}{}.with.overflow.i{}",
                                 if signed { 's' } else { 'u' },
-                                &name[..3],
+                                &name_str[..3],
                                 width
                             );
                             let llfn = self.get_intrinsic(&intrinsic);
@@ -464,61 +491,61 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
 
                             return;
                         }
-                        "wrapping_add" => self.add(args[0].immediate(), args[1].immediate()),
-                        "wrapping_sub" => self.sub(args[0].immediate(), args[1].immediate()),
-                        "wrapping_mul" => self.mul(args[0].immediate(), args[1].immediate()),
-                        "exact_div" => {
+                        sym::wrapping_add => self.add(args[0].immediate(), args[1].immediate()),
+                        sym::wrapping_sub => self.sub(args[0].immediate(), args[1].immediate()),
+                        sym::wrapping_mul => self.mul(args[0].immediate(), args[1].immediate()),
+                        sym::exact_div => {
                             if signed {
                                 self.exactsdiv(args[0].immediate(), args[1].immediate())
                             } else {
                                 self.exactudiv(args[0].immediate(), args[1].immediate())
                             }
                         }
-                        "unchecked_div" => {
+                        sym::unchecked_div => {
                             if signed {
                                 self.sdiv(args[0].immediate(), args[1].immediate())
                             } else {
                                 self.udiv(args[0].immediate(), args[1].immediate())
                             }
                         }
-                        "unchecked_rem" => {
+                        sym::unchecked_rem => {
                             if signed {
                                 self.srem(args[0].immediate(), args[1].immediate())
                             } else {
                                 self.urem(args[0].immediate(), args[1].immediate())
                             }
                         }
-                        "unchecked_shl" => self.shl(args[0].immediate(), args[1].immediate()),
-                        "unchecked_shr" => {
+                        sym::unchecked_shl => self.shl(args[0].immediate(), args[1].immediate()),
+                        sym::unchecked_shr => {
                             if signed {
                                 self.ashr(args[0].immediate(), args[1].immediate())
                             } else {
                                 self.lshr(args[0].immediate(), args[1].immediate())
                             }
                         }
-                        "unchecked_add" => {
+                        sym::unchecked_add => {
                             if signed {
                                 self.unchecked_sadd(args[0].immediate(), args[1].immediate())
                             } else {
                                 self.unchecked_uadd(args[0].immediate(), args[1].immediate())
                             }
                         }
-                        "unchecked_sub" => {
+                        sym::unchecked_sub => {
                             if signed {
                                 self.unchecked_ssub(args[0].immediate(), args[1].immediate())
                             } else {
                                 self.unchecked_usub(args[0].immediate(), args[1].immediate())
                             }
                         }
-                        "unchecked_mul" => {
+                        sym::unchecked_mul => {
                             if signed {
                                 self.unchecked_smul(args[0].immediate(), args[1].immediate())
                             } else {
                                 self.unchecked_umul(args[0].immediate(), args[1].immediate())
                             }
                         }
-                        "rotate_left" | "rotate_right" => {
-                            let is_left = name == "rotate_left";
+                        sym::rotate_left | sym::rotate_right => {
+                            let is_left = name == sym::rotate_left;
                             let val = args[0].immediate();
                             let raw_shift = args[1].immediate();
                             // rotate = funnel shift with first two args the same
@@ -527,8 +554,8 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                             let llfn = self.get_intrinsic(llvm_name);
                             self.call(llfn, &[val, val, raw_shift], None)
                         }
-                        "saturating_add" | "saturating_sub" => {
-                            let is_add = name == "saturating_add";
+                        sym::saturating_add | sym::saturating_sub => {
+                            let is_add = name == sym::saturating_add;
                             let lhs = args[0].immediate();
                             let rhs = args[1].immediate();
                             let llvm_name = &format!(
@@ -556,14 +583,14 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                     }
                 }
             }
-            "fadd_fast" | "fsub_fast" | "fmul_fast" | "fdiv_fast" | "frem_fast" => {
+            sym::fadd_fast | sym::fsub_fast | sym::fmul_fast | sym::fdiv_fast | sym::frem_fast => {
                 match float_type_width(arg_tys[0]) {
                     Some(_width) => match name {
-                        "fadd_fast" => self.fadd_fast(args[0].immediate(), args[1].immediate()),
-                        "fsub_fast" => self.fsub_fast(args[0].immediate(), args[1].immediate()),
-                        "fmul_fast" => self.fmul_fast(args[0].immediate(), args[1].immediate()),
-                        "fdiv_fast" => self.fdiv_fast(args[0].immediate(), args[1].immediate()),
-                        "frem_fast" => self.frem_fast(args[0].immediate(), args[1].immediate()),
+                        sym::fadd_fast => self.fadd_fast(args[0].immediate(), args[1].immediate()),
+                        sym::fsub_fast => self.fsub_fast(args[0].immediate(), args[1].immediate()),
+                        sym::fmul_fast => self.fmul_fast(args[0].immediate(), args[1].immediate()),
+                        sym::fdiv_fast => self.fdiv_fast(args[0].immediate(), args[1].immediate()),
+                        sym::frem_fast => self.frem_fast(args[0].immediate(), args[1].immediate()),
                         _ => bug!(),
                     },
                     None => {
@@ -581,7 +608,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 }
             }
 
-            "float_to_int_unchecked" => {
+            sym::float_to_int_unchecked => {
                 if float_type_width(arg_tys[0]).is_none() {
                     span_invalid_monomorphization_error(
                         tcx.sess,
@@ -619,7 +646,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 }
             }
 
-            "discriminant_value" => {
+            sym::discriminant_value => {
                 if ret_ty.is_integral() {
                     args[0].deref(self.cx()).codegen_get_discr(self, ret_ty)
                 } else {
@@ -627,7 +654,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 }
             }
 
-            name if name.starts_with("simd_") => {
+            _ if name_str.starts_with("simd_") => {
                 match generic_simd_intrinsic(self, name, callee_ty, args, ret_ty, llret_ty, span) {
                     Ok(llval) => llval,
                     Err(()) => return,
@@ -635,11 +662,11 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
             }
             // This requires that atomic intrinsics follow a specific naming pattern:
             // "atomic_<operation>[_<ordering>]", and no ordering means SeqCst
-            name if name.starts_with("atomic_") => {
+            name if name_str.starts_with("atomic_") => {
                 use rustc_codegen_ssa::common::AtomicOrdering::*;
                 use rustc_codegen_ssa::common::{AtomicRmwBinOp, SynchronizationScope};
 
-                let split: Vec<&str> = name.split('_').collect();
+                let split: Vec<&str> = name_str.split('_').collect();
 
                 let is_cxchg = split[1] == "cxchg" || split[1] == "cxchgweak";
                 let (order, failorder) = match split.len() {
@@ -769,23 +796,23 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 }
             }
 
-            "nontemporal_store" => {
+            sym::nontemporal_store => {
                 let dst = args[0].deref(self.cx());
                 args[1].val.nontemporal_store(self, dst);
                 return;
             }
 
-            "ptr_guaranteed_eq" | "ptr_guaranteed_ne" => {
+            sym::ptr_guaranteed_eq | sym::ptr_guaranteed_ne => {
                 let a = args[0].immediate();
                 let b = args[1].immediate();
-                if name == "ptr_guaranteed_eq" {
+                if name == sym::ptr_guaranteed_eq {
                     self.icmp(IntPredicate::IntEQ, a, b)
                 } else {
                     self.icmp(IntPredicate::IntNE, a, b)
                 }
             }
 
-            "ptr_offset_from" => {
+            sym::ptr_offset_from => {
                 let ty = substs.type_at(0);
                 let pointee_size = self.size_of(ty);
 
@@ -1172,7 +1199,7 @@ fn get_rust_try_fn<'ll, 'tcx>(
 
 fn generic_simd_intrinsic(
     bx: &mut Builder<'a, 'll, 'tcx>,
-    name: &str,
+    name: Symbol,
     callee_ty: Ty<'tcx>,
     args: &[OperandRef<'tcx, &'ll Value>],
     ret_ty: Ty<'tcx>,
@@ -1219,8 +1246,9 @@ fn generic_simd_intrinsic(
     let sig = tcx
         .normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &callee_ty.fn_sig(tcx));
     let arg_tys = sig.inputs();
+    let name_str = &*name.as_str();
 
-    if name == "simd_select_bitmask" {
+    if name == sym::simd_select_bitmask {
         let in_ty = arg_tys[0];
         let m_len = match in_ty.kind {
             // Note that this `.unwrap()` crashes for isize/usize, that's sort
@@ -1250,12 +1278,12 @@ fn generic_simd_intrinsic(
     let in_len = arg_tys[0].simd_size(tcx);
 
     let comparison = match name {
-        "simd_eq" => Some(hir::BinOpKind::Eq),
-        "simd_ne" => Some(hir::BinOpKind::Ne),
-        "simd_lt" => Some(hir::BinOpKind::Lt),
-        "simd_le" => Some(hir::BinOpKind::Le),
-        "simd_gt" => Some(hir::BinOpKind::Gt),
-        "simd_ge" => Some(hir::BinOpKind::Ge),
+        sym::simd_eq => Some(hir::BinOpKind::Eq),
+        sym::simd_ne => Some(hir::BinOpKind::Ne),
+        sym::simd_lt => Some(hir::BinOpKind::Lt),
+        sym::simd_le => Some(hir::BinOpKind::Le),
+        sym::simd_gt => Some(hir::BinOpKind::Gt),
+        sym::simd_ge => Some(hir::BinOpKind::Ge),
         _ => None,
     };
 
@@ -1289,8 +1317,8 @@ fn generic_simd_intrinsic(
         ));
     }
 
-    if name.starts_with("simd_shuffle") {
-        let n: u64 = name["simd_shuffle".len()..].parse().unwrap_or_else(|_| {
+    if name_str.starts_with("simd_shuffle") {
+        let n: u64 = name_str["simd_shuffle".len()..].parse().unwrap_or_else(|_| {
             span_bug!(span, "bad `simd_shuffle` instruction only caught in codegen?")
         });
 
@@ -1351,7 +1379,7 @@ fn generic_simd_intrinsic(
         ));
     }
 
-    if name == "simd_insert" {
+    if name == sym::simd_insert {
         require!(
             in_elem == arg_tys[2],
             "expected inserted type `{}` (element of input `{}`), found `{}`",
@@ -1365,7 +1393,7 @@ fn generic_simd_intrinsic(
             args[1].immediate(),
         ));
     }
-    if name == "simd_extract" {
+    if name == sym::simd_extract {
         require!(
             ret_ty == in_elem,
             "expected return type `{}` (element of input `{}`), found `{}`",
@@ -1376,7 +1404,7 @@ fn generic_simd_intrinsic(
         return Ok(bx.extract_element(args[0].immediate(), args[1].immediate()));
     }
 
-    if name == "simd_select" {
+    if name == sym::simd_select {
         let m_elem_ty = in_elem;
         let m_len = in_len;
         require_simd!(arg_tys[1], "argument");
@@ -1398,7 +1426,7 @@ fn generic_simd_intrinsic(
         return Ok(bx.select(m_i1s, args[1].immediate(), args[2].immediate()));
     }
 
-    if name == "simd_bitmask" {
+    if name == sym::simd_bitmask {
         // The `fn simd_bitmask(vector) -> unsigned integer` intrinsic takes a
         // vector mask and returns an unsigned integer containing the most
         // significant bit (MSB) of each lane.
@@ -1513,46 +1541,46 @@ fn generic_simd_intrinsic(
     }
 
     match name {
-        "simd_fsqrt" => {
+        sym::simd_fsqrt => {
             return simd_simple_float_intrinsic("sqrt", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_fsin" => {
+        sym::simd_fsin => {
             return simd_simple_float_intrinsic("sin", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_fcos" => {
+        sym::simd_fcos => {
             return simd_simple_float_intrinsic("cos", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_fabs" => {
+        sym::simd_fabs => {
             return simd_simple_float_intrinsic("fabs", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_floor" => {
+        sym::simd_floor => {
             return simd_simple_float_intrinsic("floor", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_ceil" => {
+        sym::simd_ceil => {
             return simd_simple_float_intrinsic("ceil", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_fexp" => {
+        sym::simd_fexp => {
             return simd_simple_float_intrinsic("exp", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_fexp2" => {
+        sym::simd_fexp2 => {
             return simd_simple_float_intrinsic("exp2", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_flog10" => {
+        sym::simd_flog10 => {
             return simd_simple_float_intrinsic("log10", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_flog2" => {
+        sym::simd_flog2 => {
             return simd_simple_float_intrinsic("log2", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_flog" => {
+        sym::simd_flog => {
             return simd_simple_float_intrinsic("log", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_fpowi" => {
+        sym::simd_fpowi => {
             return simd_simple_float_intrinsic("powi", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_fpow" => {
+        sym::simd_fpow => {
             return simd_simple_float_intrinsic("pow", in_elem, in_ty, in_len, bx, span, args);
         }
-        "simd_fma" => {
+        sym::simd_fma => {
             return simd_simple_float_intrinsic("fma", in_elem, in_ty, in_len, bx, span, args);
         }
         _ => { /* fallthrough */ }
@@ -1591,7 +1619,7 @@ fn generic_simd_intrinsic(
         cx.type_vector(elem_ty, vec_len)
     }
 
-    if name == "simd_gather" {
+    if name == sym::simd_gather {
         // simd_gather(values: <N x T>, pointers: <N x *_ T>,
         //             mask: <N x i{M}>) -> <N x T>
         // * N: number of elements in the input vectors
@@ -1718,7 +1746,7 @@ fn generic_simd_intrinsic(
         return Ok(v);
     }
 
-    if name == "simd_scatter" {
+    if name == sym::simd_scatter {
         // simd_scatter(values: <N x T>, pointers: <N x *mut T>,
         //             mask: <N x i{M}>) -> ()
         // * N: number of elements in the input vectors
@@ -1841,8 +1869,9 @@ fn generic_simd_intrinsic(
     }
 
     macro_rules! arith_red {
-        ($name:tt : $integer_reduce:ident, $float_reduce:ident, $ordered:expr) => {
-            if name == $name {
+        ($name:ident : $integer_reduce:ident, $float_reduce:ident, $ordered:expr, $op:ident,
+         $identity:expr) => {
+            if name == sym::$name {
                 require!(
                     ret_ty == in_elem,
                     "expected return type `{}` (element of input `{}`), found `{}`",
@@ -1856,11 +1885,7 @@ fn generic_simd_intrinsic(
                         if $ordered {
                             // if overflow occurs, the result is the
                             // mathematical result modulo 2^n:
-                            if name.contains("mul") {
-                                Ok(bx.mul(args[1].immediate(), r))
-                            } else {
-                                Ok(bx.add(args[1].immediate(), r))
-                            }
+                            Ok(bx.$op(args[1].immediate(), r))
                         } else {
                             Ok(bx.$integer_reduce(args[0].immediate()))
                         }
@@ -1871,14 +1896,13 @@ fn generic_simd_intrinsic(
                             args[1].immediate()
                         } else {
                             // unordered arithmetic reductions use the identity accumulator
-                            let identity_acc = if $name.contains("mul") { 1.0 } else { 0.0 };
                             match f.bit_width() {
-                                32 => bx.const_real(bx.type_f32(), identity_acc),
-                                64 => bx.const_real(bx.type_f64(), identity_acc),
+                                32 => bx.const_real(bx.type_f32(), $identity),
+                                64 => bx.const_real(bx.type_f64(), $identity),
                                 v => return_error!(
                                     r#"
 unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
-                                    $name,
+                                    sym::$name,
                                     in_ty,
                                     in_elem,
                                     v,
@@ -1890,7 +1914,7 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                     }
                     _ => return_error!(
                         "unsupported {} from `{}` with element `{}` to `{}`",
-                        $name,
+                        sym::$name,
                         in_ty,
                         in_elem,
                         ret_ty
@@ -1900,14 +1924,26 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
         };
     }
 
-    arith_red!("simd_reduce_add_ordered": vector_reduce_add, vector_reduce_fadd, true);
-    arith_red!("simd_reduce_mul_ordered": vector_reduce_mul, vector_reduce_fmul, true);
-    arith_red!("simd_reduce_add_unordered": vector_reduce_add, vector_reduce_fadd_fast, false);
-    arith_red!("simd_reduce_mul_unordered": vector_reduce_mul, vector_reduce_fmul_fast, false);
+    arith_red!(simd_reduce_add_ordered: vector_reduce_add, vector_reduce_fadd, true, add, 0.0);
+    arith_red!(simd_reduce_mul_ordered: vector_reduce_mul, vector_reduce_fmul, true, mul, 1.0);
+    arith_red!(
+        simd_reduce_add_unordered: vector_reduce_add,
+        vector_reduce_fadd_fast,
+        false,
+        add,
+        0.0
+    );
+    arith_red!(
+        simd_reduce_mul_unordered: vector_reduce_mul,
+        vector_reduce_fmul_fast,
+        false,
+        mul,
+        1.0
+    );
 
     macro_rules! minmax_red {
-        ($name:tt: $int_red:ident, $float_red:ident) => {
-            if name == $name {
+        ($name:ident: $int_red:ident, $float_red:ident) => {
+            if name == sym::$name {
                 require!(
                     ret_ty == in_elem,
                     "expected return type `{}` (element of input `{}`), found `{}`",
@@ -1921,7 +1957,7 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                     ty::Float(_f) => Ok(bx.$float_red(args[0].immediate())),
                     _ => return_error!(
                         "unsupported {} from `{}` with element `{}` to `{}`",
-                        $name,
+                        sym::$name,
                         in_ty,
                         in_elem,
                         ret_ty
@@ -1931,15 +1967,15 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
         };
     }
 
-    minmax_red!("simd_reduce_min": vector_reduce_min, vector_reduce_fmin);
-    minmax_red!("simd_reduce_max": vector_reduce_max, vector_reduce_fmax);
+    minmax_red!(simd_reduce_min: vector_reduce_min, vector_reduce_fmin);
+    minmax_red!(simd_reduce_max: vector_reduce_max, vector_reduce_fmax);
 
-    minmax_red!("simd_reduce_min_nanless": vector_reduce_min, vector_reduce_fmin_fast);
-    minmax_red!("simd_reduce_max_nanless": vector_reduce_max, vector_reduce_fmax_fast);
+    minmax_red!(simd_reduce_min_nanless: vector_reduce_min, vector_reduce_fmin_fast);
+    minmax_red!(simd_reduce_max_nanless: vector_reduce_max, vector_reduce_fmax_fast);
 
     macro_rules! bitwise_red {
-        ($name:tt : $red:ident, $boolean:expr) => {
-            if name == $name {
+        ($name:ident : $red:ident, $boolean:expr) => {
+            if name == sym::$name {
                 let input = if !$boolean {
                     require!(
                         ret_ty == in_elem,
@@ -1954,7 +1990,7 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                         ty::Int(_) | ty::Uint(_) => {}
                         _ => return_error!(
                             "unsupported {} from `{}` with element `{}` to `{}`",
-                            $name,
+                            sym::$name,
                             in_ty,
                             in_elem,
                             ret_ty
@@ -1973,7 +2009,7 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                     }
                     _ => return_error!(
                         "unsupported {} from `{}` with element `{}` to `{}`",
-                        $name,
+                        sym::$name,
                         in_ty,
                         in_elem,
                         ret_ty
@@ -1983,13 +2019,13 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
         };
     }
 
-    bitwise_red!("simd_reduce_and": vector_reduce_and, false);
-    bitwise_red!("simd_reduce_or": vector_reduce_or, false);
-    bitwise_red!("simd_reduce_xor": vector_reduce_xor, false);
-    bitwise_red!("simd_reduce_all": vector_reduce_and, true);
-    bitwise_red!("simd_reduce_any": vector_reduce_or, true);
+    bitwise_red!(simd_reduce_and: vector_reduce_and, false);
+    bitwise_red!(simd_reduce_or: vector_reduce_or, false);
+    bitwise_red!(simd_reduce_xor: vector_reduce_xor, false);
+    bitwise_red!(simd_reduce_all: vector_reduce_and, true);
+    bitwise_red!(simd_reduce_any: vector_reduce_or, true);
 
-    if name == "simd_cast" {
+    if name == sym::simd_cast {
         require_simd!(ret_ty, "return");
         let out_len = ret_ty.simd_size(tcx);
         require!(
@@ -2077,7 +2113,7 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
     }
     macro_rules! arith {
         ($($name: ident: $($($p: ident),* => $call: ident),*;)*) => {
-            $(if name == stringify!($name) {
+            $(if name == sym::$name {
                 match in_elem.kind {
                     $($(ty::$p(_))|* => {
                         return Ok(bx.$call(args[0].immediate(), args[1].immediate()))
@@ -2107,10 +2143,10 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
 
     }
 
-    if name == "simd_saturating_add" || name == "simd_saturating_sub" {
+    if name == sym::simd_saturating_add || name == sym::simd_saturating_sub {
         let lhs = args[0].immediate();
         let rhs = args[1].immediate();
-        let is_add = name == "simd_saturating_add";
+        let is_add = name == sym::simd_saturating_add;
         let ptr_bits = bx.tcx().data_layout.pointer_size.bits() as _;
         let (signed, elem_width, elem_ty) = match in_elem.kind {
             ty::Int(i) => (true, i.bit_width().unwrap_or(ptr_bits), bx.cx.type_int_from_ty(i)),

src/librustc_codegen_ssa/back/symbol_export.rs

@@ -16,6 +16,7 @@ use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
 use rustc_middle::ty::Instance;
 use rustc_middle::ty::{SymbolName, TyCtxt};
 use rustc_session::config::{CrateType, SanitizerSet};
+use rustc_span::symbol::sym;
 
 pub fn threshold(tcx: TyCtxt<'_>) -> SymbolExportLevel {
     crates_export_threshold(&tcx.sess.crate_types())
@@ -107,7 +108,7 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, cnum: CrateNum) -> DefIdMap<
         })
         .map(|def_id| {
             let export_level = if special_runtime_crate {
-                let name = tcx.symbol_name(Instance::mono(tcx, def_id.to_def_id())).name.as_str();
+                let name = tcx.symbol_name(Instance::mono(tcx, def_id.to_def_id())).name;
                 // We can probably do better here by just ensuring that
                 // it has hidden visibility rather than public
                 // visibility, as this is primarily here to ensure it's
@@ -115,13 +116,12 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, cnum: CrateNum) -> DefIdMap<
                 //
                 // In general though we won't link right if these
                 // symbols are stripped, and LTO currently strips them.
-                if name == "rust_eh_personality"
-                    || name == "rust_eh_register_frames"
-                    || name == "rust_eh_unregister_frames"
-                {
-                    SymbolExportLevel::C
-                } else {
-                    SymbolExportLevel::Rust
+                match name {
+                    sym::rust_eh_personality
+                    | sym::rust_eh_register_frames
+                    | sym::rust_eh_unregister_frames =>
+                        SymbolExportLevel::C,
+                    _ => SymbolExportLevel::Rust,
                 }
             } else {
                 symbol_export_level(tcx, def_id.to_def_id())

src/librustc_codegen_ssa/mir/block.rs

@@ -17,7 +17,8 @@ use rustc_middle::mir::interpret::{AllocId, ConstValue, Pointer, Scalar};
 use rustc_middle::mir::AssertKind;
 use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt};
 use rustc_middle::ty::{self, Instance, Ty, TypeFoldable};
-use rustc_span::{source_map::Span, symbol::Symbol};
+use rustc_span::source_map::Span;
+use rustc_span::{sym, Symbol};
 use rustc_target::abi::call::{ArgAbi, FnAbi, PassMode};
 use rustc_target::abi::{self, LayoutOf};
 use rustc_target::spec::abi::Abi;
@@ -445,7 +446,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         &mut self,
         helper: &TerminatorCodegenHelper<'tcx>,
         bx: &mut Bx,
-        intrinsic: Option<&str>,
+        intrinsic: Option<Symbol>,
         instance: Option<Instance<'tcx>>,
         span: Span,
         destination: &Option<(mir::Place<'tcx>, mir::BasicBlock)>,
@@ -461,10 +462,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             UninitValid,
         };
         let panic_intrinsic = intrinsic.and_then(|i| match i {
-            // FIXME: Move to symbols instead of strings.
-            "assert_inhabited" => Some(AssertIntrinsic::Inhabited),
-            "assert_zero_valid" => Some(AssertIntrinsic::ZeroValid),
-            "assert_uninit_valid" => Some(AssertIntrinsic::UninitValid),
+            sym::assert_inhabited => Some(AssertIntrinsic::Inhabited),
+            sym::assert_zero_valid => Some(AssertIntrinsic::ZeroValid),
+            sym::assert_uninit_valid => Some(AssertIntrinsic::UninitValid),
             _ => None,
         });
         if let Some(intrinsic) = panic_intrinsic {
@@ -568,10 +568,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
         // Handle intrinsics old codegen wants Expr's for, ourselves.
         let intrinsic = match def {
-            Some(ty::InstanceDef::Intrinsic(def_id)) => Some(bx.tcx().item_name(def_id).as_str()),
+            Some(ty::InstanceDef::Intrinsic(def_id)) => Some(bx.tcx().item_name(def_id)),
             _ => None,
         };
-        let intrinsic = intrinsic.as_ref().map(|s| &s[..]);
 
         let extra_args = &args[sig.inputs().skip_binder().len()..];
         let extra_args = extra_args
@@ -587,7 +586,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             None => FnAbi::of_fn_ptr(&bx, sig, &extra_args),
         };
 
-        if intrinsic == Some("transmute") {
+        if intrinsic == Some(sym::transmute) {
             if let Some(destination_ref) = destination.as_ref() {
                 let &(dest, target) = destination_ref;
                 self.codegen_transmute(&mut bx, &args[0], dest);
@@ -607,7 +606,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         }
 
         // For normal codegen, this Miri-specific intrinsic should never occur.
-        if intrinsic == Some("miri_start_panic") {
+        if intrinsic == Some(sym::miri_start_panic) {
             bug!("`miri_start_panic` should never end up in compiled code");
         }
 
@@ -635,7 +634,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             ReturnDest::Nothing
         };
 
-        if intrinsic == Some("caller_location") {
+        if intrinsic == Some(sym::caller_location) {
             if let Some((_, target)) = destination.as_ref() {
                 let location = self.get_caller_location(&mut bx, fn_span);
 
@@ -650,7 +649,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             return;
         }
 
-        if intrinsic.is_some() && intrinsic != Some("drop_in_place") {
+        if intrinsic.is_some() && intrinsic != Some(sym::drop_in_place) {
             let intrinsic = intrinsic.unwrap();
 
             // `is_codegen_intrinsic()` allows the backend implementation to perform compile-time
@@ -682,7 +681,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     // third argument must be constant. This is
                     // checked by const-qualification, which also
                     // promotes any complex rvalues to constants.
-                    if i == 2 && intrinsic.starts_with("simd_shuffle") {
+                    if i == 2 && intrinsic.as_str().starts_with("simd_shuffle") {
                         if let mir::Operand::Constant(constant) = arg {
                             let c = self.eval_mir_constant(constant);
                             let (llval, ty) = self.simd_shuffle_indices(

src/librustc_codegen_ssa/traits/intrinsic.rs

@@ -2,7 +2,7 @@ use super::BackendTypes;
 use crate::mir::operand::OperandRef;
 use rustc_middle::mir::Operand;
 use rustc_middle::ty::{self, Ty};
-use rustc_span::Span;
+use rustc_span::{Span, Symbol};
 use rustc_target::abi::call::FnAbi;
 
 pub trait IntrinsicCallMethods<'tcx>: BackendTypes {
@@ -24,7 +24,7 @@ pub trait IntrinsicCallMethods<'tcx>: BackendTypes {
     /// the intrinsic does not need code generation.
     fn is_codegen_intrinsic(
         &mut self,
-        intrinsic: &str,
+        intrinsic: Symbol,
         args: &Vec<Operand<'tcx>>,
         caller_instance: ty::Instance<'tcx>,
     ) -> bool;

src/librustc_driver/lib.rs

@@ -698,7 +698,7 @@ impl RustcDefaultCalls {
                         .parse_sess
                         .config
                         .iter()
-                        .filter_map(|&(name, ref value)| {
+                        .filter_map(|&(name, value)| {
                             // Note that crt-static is a specially recognized cfg
                             // directive that's printed out here as part of
                             // rust-lang/rust#37406, but in general the
@@ -707,9 +707,7 @@ impl RustcDefaultCalls {
                             // specifically allowing the crt-static cfg and that's
                             // it, this is intended to get into Cargo and then go
                             // through to build scripts.
-                            let value = value.as_ref().map(|s| s.as_str());
-                            let value = value.as_ref().map(|s| s.as_ref());
-                            if (name != sym::target_feature || value != Some("crt-static"))
+                            if (name != sym::target_feature || value != Some(sym::crt_dash_static))
                                 && !allow_unstable_cfg
                                 && find_gated_cfg(|cfg_sym| cfg_sym == name).is_some()
                             {

src/librustc_hir/lang_items.rs

@@ -16,7 +16,7 @@ use rustc_ast::ast;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_macros::HashStable_Generic;
-use rustc_span::symbol::{sym, Symbol};
+use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
 
 use lazy_static::lazy_static;
@@ -52,10 +52,10 @@ macro_rules! language_item_table {
         }
 
         impl LangItem {
-            /// Returns the `name` in `#[lang = "$name"]`.
+            /// Returns the `name` symbol in `#[lang = "$name"]`.
             /// For example, `LangItem::EqTraitLangItem`,
-            /// that is `#[lang = "eq"]` would result in `"eq"`.
-            pub fn name(self) -> &'static str {
+            /// that is `#[lang = "eq"]` would result in `sym::eq`.
+            pub fn name(self) -> Symbol {
                 match self {
                     $( $variant => $name, )*
                 }
@@ -110,9 +110,8 @@ macro_rules! language_item_table {
             }
 
             $(
-                /// Returns the corresponding `DefId` for the lang item
-                #[doc = $name]
-                /// if it exists.
+                /// Returns the corresponding `DefId` for the lang item if it
+                /// exists.
                 #[allow(dead_code)]
                 pub fn $method(&self) -> Option<DefId> {
                     self.items[$variant as usize]
@@ -122,7 +121,7 @@ macro_rules! language_item_table {
 
         lazy_static! {
             /// A mapping from the name of the lang item to its order and the form it must be of.
-            pub static ref ITEM_REFS: FxHashMap<&'static str, (usize, Target)> = {
+            pub static ref ITEM_REFS: FxHashMap<Symbol, (usize, Target)> = {
                 let mut item_refs = FxHashMap::default();
                 $( item_refs.insert($name, ($variant as usize, $target)); )*
                 item_refs
@@ -154,100 +153,100 @@ pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
 }
 
 language_item_table! {
-//  Variant name,                Name,                 Method name,             Target;
-    BoolImplItem,                "bool",               bool_impl,               Target::Impl;
-    CharImplItem,                "char",               char_impl,               Target::Impl;
-    StrImplItem,                 "str",                str_impl,                Target::Impl;
-    SliceImplItem,               "slice",              slice_impl,              Target::Impl;
-    SliceU8ImplItem,             "slice_u8",           slice_u8_impl,           Target::Impl;
-    StrAllocImplItem,            "str_alloc",          str_alloc_impl,          Target::Impl;
-    SliceAllocImplItem,          "slice_alloc",        slice_alloc_impl,        Target::Impl;
-    SliceU8AllocImplItem,        "slice_u8_alloc",     slice_u8_alloc_impl,     Target::Impl;
-    ConstPtrImplItem,            "const_ptr",          const_ptr_impl,          Target::Impl;
-    MutPtrImplItem,              "mut_ptr",            mut_ptr_impl,            Target::Impl;
-    ConstSlicePtrImplItem,       "const_slice_ptr",    const_slice_ptr_impl,    Target::Impl;
-    MutSlicePtrImplItem,         "mut_slice_ptr",      mut_slice_ptr_impl,      Target::Impl;
-    I8ImplItem,                  "i8",                 i8_impl,                 Target::Impl;
-    I16ImplItem,                 "i16",                i16_impl,                Target::Impl;
-    I32ImplItem,                 "i32",                i32_impl,                Target::Impl;
-    I64ImplItem,                 "i64",                i64_impl,                Target::Impl;
-    I128ImplItem,                "i128",               i128_impl,               Target::Impl;
-    IsizeImplItem,               "isize",              isize_impl,              Target::Impl;
-    U8ImplItem,                  "u8",                 u8_impl,                 Target::Impl;
-    U16ImplItem,                 "u16",                u16_impl,                Target::Impl;
-    U32ImplItem,                 "u32",                u32_impl,                Target::Impl;
-    U64ImplItem,                 "u64",                u64_impl,                Target::Impl;
-    U128ImplItem,                "u128",               u128_impl,               Target::Impl;
-    UsizeImplItem,               "usize",              usize_impl,              Target::Impl;
-    F32ImplItem,                 "f32",                f32_impl,                Target::Impl;
-    F64ImplItem,                 "f64",                f64_impl,                Target::Impl;
-    F32RuntimeImplItem,          "f32_runtime",        f32_runtime_impl,        Target::Impl;
-    F64RuntimeImplItem,          "f64_runtime",        f64_runtime_impl,        Target::Impl;
+//  Variant name,                  Name,                    Method name,             Target;
+    BoolImplItem,                  sym::bool,               bool_impl,               Target::Impl;
+    CharImplItem,                  sym::char,               char_impl,               Target::Impl;
+    StrImplItem,                   sym::str,                str_impl,                Target::Impl;
+    SliceImplItem,                 sym::slice,              slice_impl,              Target::Impl;
+    SliceU8ImplItem,               sym::slice_u8,           slice_u8_impl,           Target::Impl;
+    StrAllocImplItem,              sym::str_alloc,          str_alloc_impl,          Target::Impl;
+    SliceAllocImplItem,            sym::slice_alloc,        slice_alloc_impl,        Target::Impl;
+    SliceU8AllocImplItem,          sym::slice_u8_alloc,     slice_u8_alloc_impl,     Target::Impl;
+    ConstPtrImplItem,              sym::const_ptr,          const_ptr_impl,          Target::Impl;
+    MutPtrImplItem,                sym::mut_ptr,            mut_ptr_impl,            Target::Impl;
+    ConstSlicePtrImplItem,         sym::const_slice_ptr,    const_slice_ptr_impl,    Target::Impl;
+    MutSlicePtrImplItem,           sym::mut_slice_ptr,      mut_slice_ptr_impl,      Target::Impl;
+    I8ImplItem,                    sym::i8,                 i8_impl,                 Target::Impl;
+    I16ImplItem,                   sym::i16,                i16_impl,                Target::Impl;
+    I32ImplItem,                   sym::i32,                i32_impl,                Target::Impl;
+    I64ImplItem,                   sym::i64,                i64_impl,                Target::Impl;
+    I128ImplItem,                  sym::i128,               i128_impl,               Target::Impl;
+    IsizeImplItem,                 sym::isize,              isize_impl,              Target::Impl;
+    U8ImplItem,                    sym::u8,                 u8_impl,                 Target::Impl;
+    U16ImplItem,                   sym::u16,                u16_impl,                Target::Impl;
+    U32ImplItem,                   sym::u32,                u32_impl,                Target::Impl;
+    U64ImplItem,                   sym::u64,                u64_impl,                Target::Impl;
+    U128ImplItem,                  sym::u128,               u128_impl,               Target::Impl;
+    UsizeImplItem,                 sym::usize,              usize_impl,              Target::Impl;
+    F32ImplItem,                   sym::f32,                f32_impl,                Target::Impl;
+    F64ImplItem,                   sym::f64,                f64_impl,                Target::Impl;
+    F32RuntimeImplItem,            sym::f32_runtime,        f32_runtime_impl,        Target::Impl;
+    F64RuntimeImplItem,            sym::f64_runtime,        f64_runtime_impl,        Target::Impl;
 
-    SizedTraitLangItem,          "sized",              sized_trait,             Target::Trait;
-    UnsizeTraitLangItem,         "unsize",             unsize_trait,            Target::Trait;
+    SizedTraitLangItem,            sym::sized,              sized_trait,             Target::Trait;
+    UnsizeTraitLangItem,           sym::unsize,             unsize_trait,            Target::Trait;
     // trait injected by #[derive(PartialEq)], (i.e. "Partial EQ").
-    StructuralPeqTraitLangItem,  "structural_peq",     structural_peq_trait,    Target::Trait;
+    StructuralPeqTraitLangItem,    sym::structural_peq,     structural_peq_trait,    Target::Trait;
     // trait injected by #[derive(Eq)], (i.e. "Total EQ"; no, I will not apologize).
-    StructuralTeqTraitLangItem,  "structural_teq",     structural_teq_trait,    Target::Trait;
-    CopyTraitLangItem,           "copy",               copy_trait,              Target::Trait;
-    CloneTraitLangItem,          "clone",              clone_trait,             Target::Trait;
-    SyncTraitLangItem,           "sync",               sync_trait,              Target::Trait;
-    DiscriminantKindTraitLangItem,"discriminant_kind", discriminant_kind_trait, Target::Trait;
-    FreezeTraitLangItem,         "freeze",             freeze_trait,            Target::Trait;
+    StructuralTeqTraitLangItem,    sym::structural_teq,     structural_teq_trait,    Target::Trait;
+    CopyTraitLangItem,             sym::copy,               copy_trait,              Target::Trait;
+    CloneTraitLangItem,            sym::clone,              clone_trait,             Target::Trait;
+    SyncTraitLangItem,             sym::sync,               sync_trait,              Target::Trait;
+    DiscriminantKindTraitLangItem, sym::discriminant_kind,  discriminant_kind_trait, Target::Trait;
+    FreezeTraitLangItem,           sym::freeze,             freeze_trait,            Target::Trait;
 
-    DropTraitLangItem,           "drop",               drop_trait,              Target::Trait;
+    DropTraitLangItem,             sym::drop,               drop_trait,              Target::Trait;
 
-    CoerceUnsizedTraitLangItem,  "coerce_unsized",     coerce_unsized_trait,    Target::Trait;
-    DispatchFromDynTraitLangItem,"dispatch_from_dyn",  dispatch_from_dyn_trait, Target::Trait;
+    CoerceUnsizedTraitLangItem,    sym::coerce_unsized,     coerce_unsized_trait,    Target::Trait;
+    DispatchFromDynTraitLangItem,  sym::dispatch_from_dyn,  dispatch_from_dyn_trait, Target::Trait;
 
-    AddTraitLangItem(Op),        "add",                add_trait,               Target::Trait;
-    SubTraitLangItem(Op),        "sub",                sub_trait,               Target::Trait;
-    MulTraitLangItem(Op),        "mul",                mul_trait,               Target::Trait;
-    DivTraitLangItem(Op),        "div",                div_trait,               Target::Trait;
-    RemTraitLangItem(Op),        "rem",                rem_trait,               Target::Trait;
-    NegTraitLangItem(Op),        "neg",                neg_trait,               Target::Trait;
-    NotTraitLangItem(Op),        "not",                not_trait,               Target::Trait;
-    BitXorTraitLangItem(Op),     "bitxor",             bitxor_trait,            Target::Trait;
-    BitAndTraitLangItem(Op),     "bitand",             bitand_trait,            Target::Trait;
-    BitOrTraitLangItem(Op),      "bitor",              bitor_trait,             Target::Trait;
-    ShlTraitLangItem(Op),        "shl",                shl_trait,               Target::Trait;
-    ShrTraitLangItem(Op),        "shr",                shr_trait,               Target::Trait;
-    AddAssignTraitLangItem(Op),  "add_assign",         add_assign_trait,        Target::Trait;
-    SubAssignTraitLangItem(Op),  "sub_assign",         sub_assign_trait,        Target::Trait;
-    MulAssignTraitLangItem(Op),  "mul_assign",         mul_assign_trait,        Target::Trait;
-    DivAssignTraitLangItem(Op),  "div_assign",         div_assign_trait,        Target::Trait;
-    RemAssignTraitLangItem(Op),  "rem_assign",         rem_assign_trait,        Target::Trait;
-    BitXorAssignTraitLangItem(Op),"bitxor_assign",     bitxor_assign_trait,     Target::Trait;
-    BitAndAssignTraitLangItem(Op),"bitand_assign",     bitand_assign_trait,     Target::Trait;
-    BitOrAssignTraitLangItem(Op),"bitor_assign",       bitor_assign_trait,      Target::Trait;
-    ShlAssignTraitLangItem(Op),  "shl_assign",         shl_assign_trait,        Target::Trait;
-    ShrAssignTraitLangItem(Op),  "shr_assign",         shr_assign_trait,        Target::Trait;
-    IndexTraitLangItem(Op),      "index",              index_trait,             Target::Trait;
-    IndexMutTraitLangItem(Op),   "index_mut",          index_mut_trait,         Target::Trait;
+    AddTraitLangItem(Op),          sym::add,                add_trait,               Target::Trait;
+    SubTraitLangItem(Op),          sym::sub,                sub_trait,               Target::Trait;
+    MulTraitLangItem(Op),          sym::mul,                mul_trait,               Target::Trait;
+    DivTraitLangItem(Op),          sym::div,                div_trait,               Target::Trait;
+    RemTraitLangItem(Op),          sym::rem,                rem_trait,               Target::Trait;
+    NegTraitLangItem(Op),          sym::neg,                neg_trait,               Target::Trait;
+    NotTraitLangItem(Op),          sym::not,                not_trait,               Target::Trait;
+    BitXorTraitLangItem(Op),       sym::bitxor,             bitxor_trait,            Target::Trait;
+    BitAndTraitLangItem(Op),       sym::bitand,             bitand_trait,            Target::Trait;
+    BitOrTraitLangItem(Op),        sym::bitor,              bitor_trait,             Target::Trait;
+    ShlTraitLangItem(Op),          sym::shl,                shl_trait,               Target::Trait;
+    ShrTraitLangItem(Op),          sym::shr,                shr_trait,               Target::Trait;
+    AddAssignTraitLangItem(Op),    sym::add_assign,         add_assign_trait,        Target::Trait;
+    SubAssignTraitLangItem(Op),    sym::sub_assign,         sub_assign_trait,        Target::Trait;
+    MulAssignTraitLangItem(Op),    sym::mul_assign,         mul_assign_trait,        Target::Trait;
+    DivAssignTraitLangItem(Op),    sym::div_assign,         div_assign_trait,        Target::Trait;
+    RemAssignTraitLangItem(Op),    sym::rem_assign,         rem_assign_trait,        Target::Trait;
+    BitXorAssignTraitLangItem(Op), sym::bitxor_assign,      bitxor_assign_trait,     Target::Trait;
+    BitAndAssignTraitLangItem(Op), sym::bitand_assign,      bitand_assign_trait,     Target::Trait;
+    BitOrAssignTraitLangItem(Op),  sym::bitor_assign,       bitor_assign_trait,      Target::Trait;
+    ShlAssignTraitLangItem(Op),    sym::shl_assign,         shl_assign_trait,        Target::Trait;
+    ShrAssignTraitLangItem(Op),    sym::shr_assign,         shr_assign_trait,        Target::Trait;
+    IndexTraitLangItem(Op),        sym::index,              index_trait,             Target::Trait;
+    IndexMutTraitLangItem(Op),     sym::index_mut,          index_mut_trait,         Target::Trait;
 
-    UnsafeCellTypeLangItem,      "unsafe_cell",        unsafe_cell_type,        Target::Struct;
-    VaListTypeLangItem,          "va_list",            va_list,                 Target::Struct;
+    UnsafeCellTypeLangItem,        sym::unsafe_cell,        unsafe_cell_type,        Target::Struct;
+    VaListTypeLangItem,            sym::va_list,            va_list,                 Target::Struct;
 
-    DerefTraitLangItem,          "deref",              deref_trait,             Target::Trait;
-    DerefMutTraitLangItem,       "deref_mut",          deref_mut_trait,         Target::Trait;
-    ReceiverTraitLangItem,       "receiver",           receiver_trait,          Target::Trait;
+    DerefTraitLangItem,            sym::deref,              deref_trait,             Target::Trait;
+    DerefMutTraitLangItem,         sym::deref_mut,          deref_mut_trait,         Target::Trait;
+    ReceiverTraitLangItem,         sym::receiver,           receiver_trait,          Target::Trait;
 
-    FnTraitLangItem,             "fn",                 fn_trait,                Target::Trait;
-    FnMutTraitLangItem,          "fn_mut",             fn_mut_trait,            Target::Trait;
-    FnOnceTraitLangItem,         "fn_once",            fn_once_trait,           Target::Trait;
+    FnTraitLangItem,               kw::Fn,                  fn_trait,                Target::Trait;
+    FnMutTraitLangItem,            sym::fn_mut,             fn_mut_trait,            Target::Trait;
+    FnOnceTraitLangItem,           sym::fn_once,            fn_once_trait,           Target::Trait;
 
-    FnOnceOutputLangItem,        "fn_once_output",     fn_once_output,          Target::AssocTy;
+    FnOnceOutputLangItem,          sym::fn_once_output,     fn_once_output,          Target::AssocTy;
 
-    FutureTraitLangItem,         "future_trait",       future_trait,            Target::Trait;
-    GeneratorStateLangItem,      "generator_state",    gen_state,               Target::Enum;
-    GeneratorTraitLangItem,      "generator",          gen_trait,               Target::Trait;
-    UnpinTraitLangItem,          "unpin",              unpin_trait,             Target::Trait;
-    PinTypeLangItem,             "pin",                pin_type,                Target::Struct;
+    FutureTraitLangItem,           sym::future_trait,       future_trait,            Target::Trait;
+    GeneratorStateLangItem,        sym::generator_state,    gen_state,               Target::Enum;
+    GeneratorTraitLangItem,        sym::generator,          gen_trait,               Target::Trait;
+    UnpinTraitLangItem,            sym::unpin,              unpin_trait,             Target::Trait;
+    PinTypeLangItem,               sym::pin,                pin_type,                Target::Struct;
 
     // Don't be fooled by the naming here: this lang item denotes `PartialEq`, not `Eq`.
-    EqTraitLangItem,             "eq",                 eq_trait,                Target::Trait;
-    PartialOrdTraitLangItem,     "partial_ord",        partial_ord_trait,       Target::Trait;
+    EqTraitLangItem,               sym::eq,                 eq_trait,                Target::Trait;
+    PartialOrdTraitLangItem,       sym::partial_ord,        partial_ord_trait,       Target::Trait;
 
     // A number of panic-related lang items. The `panic` item corresponds to
     // divide-by-zero and various panic cases with `match`. The
@@ -258,39 +257,39 @@ language_item_table! {
     // defined to use it, but a final product is required to define it
     // somewhere. Additionally, there are restrictions on crates that use a weak
     // lang item, but do not have it defined.
-    PanicFnLangItem,             "panic",              panic_fn,                Target::Fn;
-    PanicBoundsCheckFnLangItem,  "panic_bounds_check", panic_bounds_check_fn,   Target::Fn;
-    PanicInfoLangItem,           "panic_info",         panic_info,              Target::Struct;
-    PanicLocationLangItem,       "panic_location",     panic_location,          Target::Struct;
-    PanicImplLangItem,           "panic_impl",         panic_impl,              Target::Fn;
+    PanicFnLangItem,               sym::panic,              panic_fn,                Target::Fn;
+    PanicBoundsCheckFnLangItem,    sym::panic_bounds_check, panic_bounds_check_fn,   Target::Fn;
+    PanicInfoLangItem,             sym::panic_info,         panic_info,              Target::Struct;
+    PanicLocationLangItem,         sym::panic_location,     panic_location,          Target::Struct;
+    PanicImplLangItem,             sym::panic_impl,         panic_impl,              Target::Fn;
     // Libstd panic entry point. Necessary for const eval to be able to catch it
-    BeginPanicFnLangItem,        "begin_panic",        begin_panic_fn,          Target::Fn;
+    BeginPanicFnLangItem,          sym::begin_panic,        begin_panic_fn,          Target::Fn;
 
-    ExchangeMallocFnLangItem,    "exchange_malloc",    exchange_malloc_fn,      Target::Fn;
-    BoxFreeFnLangItem,           "box_free",           box_free_fn,             Target::Fn;
-    DropInPlaceFnLangItem,       "drop_in_place",      drop_in_place_fn,        Target::Fn;
-    OomLangItem,                 "oom",                oom,                     Target::Fn;
-    AllocLayoutLangItem,         "alloc_layout",       alloc_layout,            Target::Struct;
+    ExchangeMallocFnLangItem,      sym::exchange_malloc,    exchange_malloc_fn,      Target::Fn;
+    BoxFreeFnLangItem,             sym::box_free,           box_free_fn,             Target::Fn;
+    DropInPlaceFnLangItem,         sym::drop_in_place,      drop_in_place_fn,        Target::Fn;
+    OomLangItem,                   sym::oom,                oom,                     Target::Fn;
+    AllocLayoutLangItem,           sym::alloc_layout,       alloc_layout,            Target::Struct;
 
-    StartFnLangItem,             "start",              start_fn,                Target::Fn;
+    StartFnLangItem,               sym::start,              start_fn,                Target::Fn;
 
-    CountCodeRegionFnLangItem,   "count_code_region",  count_code_region_fn,    Target::Fn;
+    CountCodeRegionFnLangItem,     sym::count_code_region,  count_code_region_fn,    Target::Fn;
 
-    EhPersonalityLangItem,       "eh_personality",     eh_personality,          Target::Fn;
-    EhCatchTypeinfoLangItem,     "eh_catch_typeinfo",  eh_catch_typeinfo,       Target::Static;
+    EhPersonalityLangItem,         sym::eh_personality,     eh_personality,          Target::Fn;
+    EhCatchTypeinfoLangItem,       sym::eh_catch_typeinfo,  eh_catch_typeinfo,       Target::Static;
 
-    OwnedBoxLangItem,            "owned_box",          owned_box,               Target::Struct;
+    OwnedBoxLangItem,              sym::owned_box,          owned_box,               Target::Struct;
 
-    PhantomDataItem,             "phantom_data",       phantom_data,            Target::Struct;
+    PhantomDataItem,               sym::phantom_data,       phantom_data,            Target::Struct;
 
-    ManuallyDropItem,            "manually_drop",      manually_drop,           Target::Struct;
+    ManuallyDropItem,              sym::manually_drop,      manually_drop,           Target::Struct;
 
-    MaybeUninitLangItem,         "maybe_uninit",       maybe_uninit,            Target::Union;
+    MaybeUninitLangItem,           sym::maybe_uninit,       maybe_uninit,            Target::Union;
 
     // Align offset for stride != 1; must not panic.
-    AlignOffsetLangItem,         "align_offset",       align_offset_fn,         Target::Fn;
+    AlignOffsetLangItem,           sym::align_offset,       align_offset_fn,         Target::Fn;
 
-    TerminationTraitLangItem,    "termination",        termination,             Target::Trait;
+    TerminationTraitLangItem,      sym::termination,        termination,             Target::Trait;
 
-    TryTraitLangItem,            "try",                try_trait,               Target::Trait;
+    TryTraitLangItem,              kw::Try,                 try_trait,               Target::Trait;
 }

src/librustc_incremental/assert_module_sources.rs

@@ -62,11 +62,11 @@ impl AssertModuleSource<'tcx> {
         } else if attr.check_name(sym::rustc_partition_codegened) {
             (CguReuse::No, ComparisonKind::Exact)
         } else if attr.check_name(sym::rustc_expected_cgu_reuse) {
-            match &*self.field(attr, sym::kind).as_str() {
-                "no" => (CguReuse::No, ComparisonKind::Exact),
-                "pre-lto" => (CguReuse::PreLto, ComparisonKind::Exact),
-                "post-lto" => (CguReuse::PostLto, ComparisonKind::Exact),
-                "any" => (CguReuse::PreLto, ComparisonKind::AtLeast),
+            match self.field(attr, sym::kind) {
+                sym::no => (CguReuse::No, ComparisonKind::Exact),
+                sym::pre_dash_lto => (CguReuse::PreLto, ComparisonKind::Exact),
+                sym::post_dash_lto => (CguReuse::PostLto, ComparisonKind::Exact),
+                sym::any => (CguReuse::PreLto, ComparisonKind::AtLeast),
                 other => {
                     self.tcx.sess.span_fatal(
                         attr.span,

src/librustc_interface/util.rs

@@ -53,7 +53,7 @@ pub fn add_configuration(
     cfg.extend(target_features.into_iter().map(|feat| (tf, Some(feat))));
 
     if sess.crt_static(None) {
-        cfg.insert((tf, Some(Symbol::intern("crt-static"))));
+        cfg.insert((tf, Some(sym::crt_dash_static)));
     }
 }
 

src/librustc_metadata/creader.rs

@@ -679,8 +679,8 @@ impl<'a> CrateLoader<'a> {
         // in terms of everyone has a compatible panic runtime format, that's
         // performed later as part of the `dependency_format` module.
         let name = match desired_strategy {
-            PanicStrategy::Unwind => Symbol::intern("panic_unwind"),
-            PanicStrategy::Abort => Symbol::intern("panic_abort"),
+            PanicStrategy::Unwind => sym::panic_unwind,
+            PanicStrategy::Abort => sym::panic_abort,
         };
         info!("panic runtime not found -- loading {}", name);
 
@@ -713,7 +713,7 @@ impl<'a> CrateLoader<'a> {
         {
             info!("loading profiler");
 
-            let name = Symbol::intern("profiler_builtins");
+            let name = sym::profiler_builtins;
             let cnum = self.resolve_crate(name, DUMMY_SP, DepKind::Implicit, None);
             let data = self.cstore.get_crate_data(cnum);
 

src/librustc_mir/borrow_check/diagnostics/move_errors.rs

@@ -2,7 +2,7 @@ use rustc_errors::{Applicability, DiagnosticBuilder};
 use rustc_middle::mir::*;
 use rustc_middle::ty;
 use rustc_span::source_map::DesugaringKind;
-use rustc_span::{Span, Symbol};
+use rustc_span::{sym, Span};
 
 use crate::borrow_check::diagnostics::UseSpans;
 use crate::borrow_check::prefixes::PrefixSet;
@@ -394,10 +394,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 | ty::Opaque(def_id, _) => def_id,
                 _ => return err,
             };
-            let is_option =
-                self.infcx.tcx.is_diagnostic_item(Symbol::intern("option_type"), def_id);
-            let is_result =
-                self.infcx.tcx.is_diagnostic_item(Symbol::intern("result_type"), def_id);
+            let is_option = self.infcx.tcx.is_diagnostic_item(sym::option_type, def_id);
+            let is_result = self.infcx.tcx.is_diagnostic_item(sym::result_type, def_id);
             if (is_option || is_result) && use_spans.map_or(true, |v| !v.for_closure()) {
                 err.span_suggestion(
                     span,
@@ -409,7 +407,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     Applicability::MaybeIncorrect,
                 );
             } else if matches!(span.desugaring_kind(), Some(DesugaringKind::ForLoop(_)))
-                && self.infcx.tcx.is_diagnostic_item(Symbol::intern("vec_type"), def_id)
+                && self.infcx.tcx.is_diagnostic_item(sym::vec_type, def_id)
             {
                 // FIXME: suggest for anything that implements `IntoIterator`.
                 err.span_suggestion(

src/librustc_passes/lang_items.rs

@@ -57,7 +57,7 @@ impl LanguageItemCollector<'tcx> {
 
     fn check_for_lang(&mut self, actual_target: Target, hir_id: HirId, attrs: &[Attribute]) {
         if let Some((value, span)) = extract(&attrs) {
-            match ITEM_REFS.get(&*value.as_str()).cloned() {
+            match ITEM_REFS.get(&value).cloned() {
                 // Known lang item with attribute on correct target.
                 Some((item_index, expected_target)) if actual_target == expected_target => {
                     let def_id = self.tcx.hir().local_def_id(hir_id);

src/librustc_passes/stability.rs

@@ -620,7 +620,7 @@ pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
     // available as we'd like it to be.
     // FIXME: only remove `libc` when `stdbuild` is active.
     // FIXME: remove special casing for `test`.
-    remaining_lib_features.remove(&Symbol::intern("libc"));
+    remaining_lib_features.remove(&sym::libc);
     remaining_lib_features.remove(&sym::test);
 
     let check_features = |remaining_lib_features: &mut FxHashMap<_, _>, defined_features: &[_]| {

src/librustc_passes/weak_lang_items.rs

@@ -81,7 +81,7 @@ impl<'a, 'tcx> Context<'a, 'tcx> {
             // `core::intrinsics::code_count_region()` is (currently) the only `extern` lang item
             // that is never actually linked. It is not a `weak_lang_item` that can be registered
             // when used, and should be registered here instead.
-            if let Some((item_index, _)) = ITEM_REFS.get(&*name.as_str()).cloned() {
+            if let Some((item_index, _)) = ITEM_REFS.get(&name).cloned() {
                 if self.items.items[item_index].is_none() {
                     let item_def_id = self.tcx.hir().local_def_id(hir_id).to_def_id();
                     self.items.items[item_index] = Some(item_def_id);

src/librustc_resolve/diagnostics.rs

@@ -16,7 +16,7 @@ use rustc_middle::ty::{self, DefIdTree};
 use rustc_session::Session;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::source_map::SourceMap;
-use rustc_span::symbol::{kw, Ident, Symbol};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, MultiSpan, Span};
 
 use crate::imports::{Import, ImportKind, ImportResolver};
@@ -882,8 +882,7 @@ impl<'a> Resolver<'a> {
         );
         self.add_typo_suggestion(err, suggestion, ident.span);
 
-        if macro_kind == MacroKind::Derive && (ident.as_str() == "Send" || ident.as_str() == "Sync")
-        {
+        if macro_kind == MacroKind::Derive && (ident.name == sym::Send || ident.name == sym::Sync) {
             let msg = format!("unsafe traits like `{}` should be implemented explicitly", ident);
             err.span_note(ident.span, &msg);
         }

src/librustc_resolve/imports.rs

@@ -1034,8 +1034,7 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                         let initial_res = source_bindings[ns].get().map(|initial_binding| {
                             all_ns_err = false;
                             if let Some(target_binding) = target_bindings[ns].get() {
-                                // Note that as_str() de-gensyms the Symbol
-                                if target.name.as_str() == "_"
+                                if target.name == kw::Underscore
                                     && initial_binding.is_extern_crate()
                                     && !initial_binding.is_import()
                                 {

src/librustc_resolve/late/lifetimes.rs

@@ -2364,7 +2364,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
         if let Some(params) = error {
             // If there's no lifetime available, suggest `'static`.
             if self.report_elision_failure(&mut err, params) && lifetime_names.is_empty() {
-                lifetime_names.insert(Ident::from_str("'static"));
+                lifetime_names.insert(Ident::with_dummy_span(kw::StaticLifetime));
             }
         }
         self.add_missing_lifetime_specifiers_label(

src/librustc_session/config.rs

@@ -717,18 +717,20 @@ pub fn default_configuration(sess: &Session) -> CrateConfig {
     let mut ret = FxHashSet::default();
     ret.reserve(6); // the minimum number of insertions
     // Target bindings.
-    ret.insert((Symbol::intern("target_os"), Some(Symbol::intern(os))));
+    ret.insert((sym::target_os, Some(Symbol::intern(os))));
     if let Some(ref fam) = sess.target.target.options.target_family {
-        ret.insert((Symbol::intern("target_family"), Some(Symbol::intern(fam))));
-        if fam == "windows" || fam == "unix" {
-            ret.insert((Symbol::intern(fam), None));
+        ret.insert((sym::target_family, Some(Symbol::intern(fam))));
+        if fam == "windows" {
+            ret.insert((sym::windows, None));
+        } else if fam == "unix" {
+            ret.insert((sym::unix, None));
         }
     }
-    ret.insert((Symbol::intern("target_arch"), Some(Symbol::intern(arch))));
-    ret.insert((Symbol::intern("target_endian"), Some(Symbol::intern(end))));
-    ret.insert((Symbol::intern("target_pointer_width"), Some(Symbol::intern(wordsz))));
-    ret.insert((Symbol::intern("target_env"), Some(Symbol::intern(env))));
-    ret.insert((Symbol::intern("target_vendor"), Some(Symbol::intern(vendor))));
+    ret.insert((sym::target_arch, Some(Symbol::intern(arch))));
+    ret.insert((sym::target_endian, Some(Symbol::intern(end))));
+    ret.insert((sym::target_pointer_width, Some(Symbol::intern(wordsz))));
+    ret.insert((sym::target_env, Some(Symbol::intern(env))));
+    ret.insert((sym::target_vendor, Some(Symbol::intern(vendor))));
     if sess.target.target.options.has_elf_tls {
         ret.insert((sym::target_thread_local, None));
     }
@@ -754,7 +756,7 @@ pub fn default_configuration(sess: &Session) -> CrateConfig {
     }
 
     if sess.opts.debug_assertions {
-        ret.insert((Symbol::intern("debug_assertions"), None));
+        ret.insert((sym::debug_assertions, None));
     }
     if sess.opts.crate_types.contains(&CrateType::ProcMacro) {
         ret.insert((sym::proc_macro, None));

src/librustc_span/symbol.rs

@@ -129,17 +129,23 @@ symbols! {
         abi_x86_interrupt,
         abort,
         aborts,
+        add,
+        add_assign,
         address,
         add_with_overflow,
         advanced_slice_patterns,
         adx_target_feature,
         alias,
         align,
+        align_offset,
         alignstack,
         all,
+        alloc,
         allocator,
         allocator_internals,
         alloc_error_handler,
+        alloc_layout,
+        alloc_zeroed,
         allow,
         allowed,
         allow_fail,
@@ -156,15 +162,18 @@ symbols! {
         ArgumentV1,
         arith_offset,
         arm_target_feature,
+        array,
         asm,
         assert,
         assert_inhabited,
+        assert_receiver_is_total_eq,
         assert_uninit_valid,
         assert_zero_valid,
         associated_consts,
         associated_type_bounds,
         associated_type_defaults,
         associated_types,
+        as_str,
         assume,
         assume_init,
         async_await,
@@ -183,19 +192,29 @@ symbols! {
         bin,
         bind_by_move_pattern_guards,
         bindings_after_at,
+        bitand,
+        bitand_assign,
+        bitor,
+        bitor_assign,
         bitreverse,
+        bitxor,
+        bitxor_assign,
         block,
         bool,
         borrowck_graphviz_format,
         borrowck_graphviz_postflow,
         borrowck_graphviz_preflow,
+        box_free,
         box_patterns,
         box_syntax,
         braced_empty_structs,
         breakpoint,
         bswap,
         C,
+        call,
         caller_location,
+        call_mut,
+        call_once,
         cdylib,
         ceilf32,
         ceilf64,
@@ -219,6 +238,7 @@ symbols! {
         closure_to_fn_coercion,
         cmp,
         cmpxchg16b_target_feature,
+        coerce_unsized,
         cold,
         column,
         compile_error,
@@ -243,8 +263,10 @@ symbols! {
         const_mut_refs,
         const_panic,
         const_precise_live_drops,
+        const_ptr,
         const_raw_ptr_deref,
         const_raw_ptr_to_usize_cast,
+        const_slice_ptr,
         const_trait_bound_opt_out,
         const_trait_impl,
         const_transmute,
@@ -271,6 +293,7 @@ symbols! {
         crate_name,
         crate_type,
         crate_visibility_modifier,
+        crt_dash_static: "crt-static",
         ctlz,
         ctlz_nonzero,
         ctpop,
@@ -281,12 +304,16 @@ symbols! {
         custom_inner_attributes,
         custom_test_frameworks,
         c_variadic,
+        dead_code,
+        dealloc,
         debug,
         Debug,
+        debug_assertions,
         debug_trait,
         declare_lint_pass,
         decl_macro,
         Decodable,
+        decode,
         Default,
         default_lib_allocator,
         default_type_parameter_fallback,
@@ -299,7 +326,11 @@ symbols! {
         derive,
         diagnostic,
         direct,
+        discriminant_kind,
         discriminant_value,
+        dispatch_from_dyn,
+        div,
+        div_assign,
         doc,
         doc_alias,
         doc_cfg,
@@ -316,16 +347,19 @@ symbols! {
         double_braced_impl: "{{impl}}",
         double_braced_misc: "{{misc}}",
         double_braced_opaque: "{{opaque}}",
+        drop,
         dropck_eyepatch,
         dropck_parametricity,
         drop_in_place,
         drop_types_in_const,
         dylib,
         dyn_trait,
+        eh_catch_typeinfo,
         eh_personality,
         enable,
         enclosing_scope,
         Encodable,
+        encode,
         env,
         eq,
         Eq,
@@ -334,6 +368,7 @@ symbols! {
         Err,
         exact_div,
         except,
+        exchange_malloc,
         exclusive_range_pattern,
         exhaustive_integer_patterns,
         exhaustive_patterns,
@@ -354,7 +389,9 @@ symbols! {
         extern_types,
         f16c_target_feature,
         f32,
+        f32_runtime,
         f64,
+        f64_runtime,
         fabsf32,
         fabsf64,
         fadd_fast,
@@ -375,11 +412,15 @@ symbols! {
         fmt_internals,
         fmul_fast,
         fn_must_use,
+        fn_mut,
+        fn_once,
+        fn_once_output,
         forbid,
         forget,
         format_args,
         format_args_capture,
         format_args_nl,
+        freeze,
         frem_fast,
         from,
         From,
@@ -388,23 +429,30 @@ symbols! {
         from_generator,
         from_method,
         from_ok,
+        from_size_align_unchecked,
         from_trait,
         from_usize,
         fsub_fast,
         fundamental,
         future,
         Future,
+        future_trait,
         FxHashMap,
         FxHashSet,
+        ge,
+        generator,
         generators,
+        generator_state,
         generic_associated_types,
         generic_param_attrs,
         gen_future,
         gen_kill,
         get_context,
+        GlobalAlloc,
         global_allocator,
         global_asm,
         globs,
+        gt,
         half_open_range_patterns,
         hash,
         Hash,
@@ -467,10 +515,13 @@ symbols! {
         lang,
         lang_items,
         lateout,
+        Layout,
         lazy_normalization_consts,
+        le,
         let_chains,
         lhs,
         lib,
+        libc,
         lifetime,
         likely,
         line,
@@ -495,6 +546,7 @@ symbols! {
         logf64,
         log_syntax,
         loop_break_value,
+        lt,
         macro_at_most_once_rep,
         macro_escape,
         macro_export,
@@ -506,6 +558,7 @@ symbols! {
         macro_vis_matcher,
         main,
         managed_boxes,
+        manually_drop,
         marker,
         marker_trait_attr,
         masked,
@@ -513,6 +566,7 @@ symbols! {
         match_default_bindings,
         maxnumf32,
         maxnumf64,
+        maybe_uninit,
         maybe_uninit_uninit,
         maybe_uninit_zeroed,
         may_dangle,
@@ -538,16 +592,22 @@ symbols! {
         movbe_target_feature,
         move_ref_pattern,
         move_val_init,
+        mul,
+        mul_assign,
         mul_with_overflow,
         must_use,
+        mut_ptr,
+        mut_slice_ptr,
         naked,
         naked_functions,
         name,
+        ne,
         nearbyintf32,
         nearbyintf64,
         needs_allocator,
         needs_drop,
         needs_panic_runtime,
+        neg,
         negate_unsigned,
         negative_impls,
         never,
@@ -557,6 +617,7 @@ symbols! {
         __next,
         next,
         nll,
+        no,
         no_builtins,
         no_core,
         no_crate_inject,
@@ -590,6 +651,7 @@ symbols! {
         on,
         on_unimplemented,
         oom,
+        opaque,
         ops,
         optimize,
         optimize_attribute,
@@ -598,6 +660,7 @@ symbols! {
         Option,
         option_env,
         options,
+        option_type,
         opt_out_copy,
         or,
         Ord,
@@ -606,22 +669,30 @@ symbols! {
         out,
         Output,
         overlapping_marker_traits,
+        owned_box,
         packed,
         panic,
+        panic_abort,
+        panic_bounds_check,
         panic_handler,
         panic_impl,
         panic_implementation,
+        panic_info,
+        panic_location,
         panic_runtime,
+        panic_unwind,
         param_attrs,
         parent_trait,
         partial_cmp,
         PartialEq,
+        partial_ord,
         PartialOrd,
         passes,
         pat,
         path,
         pattern_parentheses,
         Pending,
+        phantom_data,
         pin,
         Pin,
         pinned,
@@ -629,14 +700,17 @@ symbols! {
         plugin,
         plugin_registrar,
         plugins,
+        pointer,
         poll,
         Poll,
+        post_dash_lto: "post-lto",
         powerpc_target_feature,
         powf32,
         powf64,
         powif32,
         powif64,
         precise_pointer_size_matching,
+        pre_dash_lto: "pre-lto",
         pref_align_of,
         prefetch_read_data,
         prefetch_read_instruction,
@@ -683,13 +757,18 @@ symbols! {
         Rc,
         readonly,
         Ready,
+        realloc,
         reason,
+        receiver,
         recursion_limit,
         reexport_test_harness_main,
+        reference,
         reflect,
         register_attr,
         register_tool,
         relaxed_adts,
+        rem,
+        rem_assign,
         repr,
         repr128,
         repr_align,
@@ -701,6 +780,7 @@ symbols! {
         re_rebalance_coherence,
         result,
         Result,
+        result_type,
         Return,
         rhs,
         rintf32,
@@ -776,6 +856,8 @@ symbols! {
         rustc_unsafe_specialization_marker,
         rustc_variance,
         rust_eh_personality,
+        rust_eh_register_frames,
+        rust_eh_unregister_frames,
         rustfmt,
         rust_oom,
         rvalue_static_promotion,
@@ -786,19 +868,83 @@ symbols! {
         _Self,
         self_in_typedefs,
         self_struct_ctor,
+        semitransparent,
+        Send,
         send_trait,
+        shl,
+        shl_assign,
         should_panic,
+        shr,
+        shr_assign,
         simd,
+        simd_add,
+        simd_and,
+        simd_bitmask,
+        simd_cast,
+        simd_ceil,
+        simd_div,
+        simd_eq,
         simd_extract,
+        simd_fabs,
+        simd_fcos,
+        simd_fexp,
+        simd_fexp2,
         simd_ffi,
+        simd_flog,
+        simd_flog10,
+        simd_flog2,
+        simd_floor,
+        simd_fma,
+        simd_fmax,
+        simd_fmin,
+        simd_fpow,
+        simd_fpowi,
+        simd_fsin,
+        simd_fsqrt,
+        simd_gather,
+        simd_ge,
+        simd_gt,
         simd_insert,
+        simd_le,
+        simd_lt,
+        simd_mul,
+        simd_ne,
+        simd_or,
+        simd_reduce_add_ordered,
+        simd_reduce_add_unordered,
+        simd_reduce_all,
+        simd_reduce_and,
+        simd_reduce_any,
+        simd_reduce_max,
+        simd_reduce_max_nanless,
+        simd_reduce_min,
+        simd_reduce_min_nanless,
+        simd_reduce_mul_ordered,
+        simd_reduce_mul_unordered,
+        simd_reduce_or,
+        simd_reduce_xor,
+        simd_rem,
+        simd_saturating_add,
+        simd_saturating_sub,
+        simd_scatter,
+        simd_select,
+        simd_select_bitmask,
+        simd_shl,
+        simd_shr,
+        simd_sub,
+        simd_xor,
         since,
         sinf32,
         sinf64,
         size,
+        sized,
         size_of,
         size_of_val,
+        slice,
+        slice_alloc,
         slice_patterns,
+        slice_u8,
+        slice_u8_alloc,
         slicing_syntax,
         soft,
         Some,
@@ -820,24 +966,41 @@ symbols! {
         stmt_expr_attributes,
         stop_after_dataflow,
         str,
+        str_alloc,
         stringify,
         struct_field_attributes,
         struct_inherit,
         structural_match,
+        structural_peq,
+        structural_teq,
         struct_variant,
         sty,
+        sub,
+        sub_assign,
         sub_with_overflow,
         suggestion,
         sym,
+        sync,
+        Sync,
         sync_trait,
+        Target,
+        target_arch,
+        target_endian,
+        target_env,
+        target_family,
         target_feature,
         target_feature_11,
         target_has_atomic,
         target_has_atomic_load_store,
+        target_os,
+        target_pointer_width,
+        target_target_vendor,
         target_thread_local,
+        target_vendor,
         task,
         _task_context,
         tbm_target_feature,
+        termination,
         termination_trait,
         termination_trait_test,
         test,
@@ -865,6 +1028,7 @@ symbols! {
         try_blocks,
         try_trait,
         tt,
+        tuple,
         tuple_indexing,
         two_phase,
         ty,
@@ -897,18 +1061,24 @@ symbols! {
         underscore_imports,
         underscore_lifetimes,
         uniform_paths,
+        unit,
         universal_impl_trait,
+        unix,
         unlikely,
         unmarked_api,
+        unpin,
         unreachable,
         unreachable_code,
         unrestricted_attribute_tokens,
         unsafe_block_in_unsafe_fn,
+        unsafe_cell,
         unsafe_no_drop_flag,
+        unsize,
         unsized_locals,
         unsized_tuple_coercion,
         unstable,
         untagged_unions,
+        unused_qualifications,
         unwind,
         unwind_attributes,
         unwrap_or,
@@ -921,11 +1091,13 @@ symbols! {
         va_copy,
         va_end,
         val,
+        va_list,
         var,
         variant_count,
         va_start,
         vec,
         Vec,
+        vec_type,
         version,
         vis,
         visible_private_types,

src/librustc_trait_selection/autoderef.rs

@@ -6,7 +6,7 @@ use rustc_infer::infer::InferCtxt;
 use rustc_middle::ty::{self, TraitRef, Ty, TyCtxt, WithConstness};
 use rustc_middle::ty::{ToPredicate, TypeFoldable};
 use rustc_session::DiagnosticMessageId;
-use rustc_span::symbol::Ident;
+use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 
 #[derive(Copy, Clone, Debug)]
@@ -143,7 +143,11 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
         let normalized_ty = fulfillcx.normalize_projection_type(
             &self.infcx,
             self.param_env,
-            ty::ProjectionTy::from_ref_and_name(tcx, trait_ref, Ident::from_str("Target")),
+            ty::ProjectionTy::from_ref_and_name(
+                tcx,
+                trait_ref,
+                Ident::with_dummy_span(sym::Target),
+            ),
             cause,
         );
         if let Err(e) = fulfillcx.select_where_possible(&self.infcx) {

src/librustc_typeck/astconv.rs

@@ -1247,7 +1247,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             .generic_args()
                             .bindings
                             .iter()
-                            .find_map(|b| match (b.ident.as_str() == "Output", &b.kind) {
+                            .find_map(|b| match (b.ident.name == sym::Output, &b.kind) {
                                 (true, hir::TypeBindingKind::Equality { ty }) => {
                                     sess.source_map().span_to_snippet(ty.span).ok()
                                 }

src/librustc_typeck/check/callee.rs

@@ -13,7 +13,7 @@ use rustc_middle::ty::adjustment::{
 };
 use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
-use rustc_span::symbol::Ident;
+use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 use rustc_target::spec::abi;
 use rustc_trait_selection::autoderef::Autoderef;
@@ -192,9 +192,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> Option<(Option<Adjustment<'tcx>>, MethodCallee<'tcx>)> {
         // Try the options that are least restrictive on the caller first.
         for &(opt_trait_def_id, method_name, borrow) in &[
-            (self.tcx.lang_items().fn_trait(), Ident::from_str("call"), true),
-            (self.tcx.lang_items().fn_mut_trait(), Ident::from_str("call_mut"), true),
-            (self.tcx.lang_items().fn_once_trait(), Ident::from_str("call_once"), false),
+            (self.tcx.lang_items().fn_trait(), Ident::with_dummy_span(sym::call), true),
+            (self.tcx.lang_items().fn_mut_trait(), Ident::with_dummy_span(sym::call_mut), true),
+            (self.tcx.lang_items().fn_once_trait(), Ident::with_dummy_span(sym::call_once), false),
         ] {
             let trait_def_id = match opt_trait_def_id {
                 Some(def_id) => def_id,

src/librustc_typeck/check/intrinsic.rs

@@ -423,70 +423,81 @@ pub fn check_platform_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>)
     };
 
     let def_id = tcx.hir().local_def_id(it.hir_id).to_def_id();
-    let name = it.ident.as_str();
+    let name = it.ident.name;
 
-    let (n_tps, inputs, output) = match &*name {
-        "simd_eq" | "simd_ne" | "simd_lt" | "simd_le" | "simd_gt" | "simd_ge" => {
+    let (n_tps, inputs, output) = match name {
+        sym::simd_eq | sym::simd_ne | sym::simd_lt | sym::simd_le | sym::simd_gt | sym::simd_ge => {
             (2, vec![param(0), param(0)], param(1))
         }
-        "simd_add"
-        | "simd_sub"
-        | "simd_mul"
-        | "simd_rem"
-        | "simd_div"
-        | "simd_shl"
-        | "simd_shr"
-        | "simd_and"
-        | "simd_or"
-        | "simd_xor"
-        | "simd_fmin"
-        | "simd_fmax"
-        | "simd_fpow"
-        | "simd_saturating_add"
-        | "simd_saturating_sub" => (1, vec![param(0), param(0)], param(0)),
-        "simd_fsqrt" | "simd_fsin" | "simd_fcos" | "simd_fexp" | "simd_fexp2" | "simd_flog2"
-        | "simd_flog10" | "simd_flog" | "simd_fabs" | "simd_floor" | "simd_ceil" => {
-            (1, vec![param(0)], param(0))
+        sym::simd_add
+        | sym::simd_sub
+        | sym::simd_mul
+        | sym::simd_rem
+        | sym::simd_div
+        | sym::simd_shl
+        | sym::simd_shr
+        | sym::simd_and
+        | sym::simd_or
+        | sym::simd_xor
+        | sym::simd_fmin
+        | sym::simd_fmax
+        | sym::simd_fpow
+        | sym::simd_saturating_add
+        | sym::simd_saturating_sub => (1, vec![param(0), param(0)], param(0)),
+        sym::simd_fsqrt
+        | sym::simd_fsin
+        | sym::simd_fcos
+        | sym::simd_fexp
+        | sym::simd_fexp2
+        | sym::simd_flog2
+        | sym::simd_flog10
+        | sym::simd_flog
+        | sym::simd_fabs
+        | sym::simd_floor
+        | sym::simd_ceil => (1, vec![param(0)], param(0)),
+        sym::simd_fpowi => (1, vec![param(0), tcx.types.i32], param(0)),
+        sym::simd_fma => (1, vec![param(0), param(0), param(0)], param(0)),
+        sym::simd_gather => (3, vec![param(0), param(1), param(2)], param(0)),
+        sym::simd_scatter => (3, vec![param(0), param(1), param(2)], tcx.mk_unit()),
+        sym::simd_insert => (2, vec![param(0), tcx.types.u32, param(1)], param(0)),
+        sym::simd_extract => (2, vec![param(0), tcx.types.u32], param(1)),
+        sym::simd_cast => (2, vec![param(0)], param(1)),
+        sym::simd_bitmask => (2, vec![param(0)], param(1)),
+        sym::simd_select | sym::simd_select_bitmask => {
+            (2, vec![param(0), param(1), param(1)], param(1))
         }
-        "simd_fpowi" => (1, vec![param(0), tcx.types.i32], param(0)),
-        "simd_fma" => (1, vec![param(0), param(0), param(0)], param(0)),
-        "simd_gather" => (3, vec![param(0), param(1), param(2)], param(0)),
-        "simd_scatter" => (3, vec![param(0), param(1), param(2)], tcx.mk_unit()),
-        "simd_insert" => (2, vec![param(0), tcx.types.u32, param(1)], param(0)),
-        "simd_extract" => (2, vec![param(0), tcx.types.u32], param(1)),
-        "simd_cast" => (2, vec![param(0)], param(1)),
-        "simd_bitmask" => (2, vec![param(0)], param(1)),
-        "simd_select" | "simd_select_bitmask" => (2, vec![param(0), param(1), param(1)], param(1)),
-        "simd_reduce_all" | "simd_reduce_any" => (1, vec![param(0)], tcx.types.bool),
-        "simd_reduce_add_ordered" | "simd_reduce_mul_ordered" => {
+        sym::simd_reduce_all | sym::simd_reduce_any => (1, vec![param(0)], tcx.types.bool),
+        sym::simd_reduce_add_ordered | sym::simd_reduce_mul_ordered => {
             (2, vec![param(0), param(1)], param(1))
         }
-        "simd_reduce_add_unordered"
-        | "simd_reduce_mul_unordered"
-        | "simd_reduce_and"
-        | "simd_reduce_or"
-        | "simd_reduce_xor"
-        | "simd_reduce_min"
-        | "simd_reduce_max"
-        | "simd_reduce_min_nanless"
-        | "simd_reduce_max_nanless" => (2, vec![param(0)], param(1)),
-        name if name.starts_with("simd_shuffle") => match name["simd_shuffle".len()..].parse() {
-            Ok(n) => {
-                let params = vec![param(0), param(0), tcx.mk_array(tcx.types.u32, n)];
-                (2, params, param(1))
+        sym::simd_reduce_add_unordered
+        | sym::simd_reduce_mul_unordered
+        | sym::simd_reduce_and
+        | sym::simd_reduce_or
+        | sym::simd_reduce_xor
+        | sym::simd_reduce_min
+        | sym::simd_reduce_max
+        | sym::simd_reduce_min_nanless
+        | sym::simd_reduce_max_nanless => (2, vec![param(0)], param(1)),
+        name if name.as_str().starts_with("simd_shuffle") => {
+            match name.as_str()["simd_shuffle".len()..].parse() {
+                Ok(n) => {
+                    let params = vec![param(0), param(0), tcx.mk_array(tcx.types.u32, n)];
+                    (2, params, param(1))
+                }
+                Err(_) => {
+                    struct_span_err!(
+                        tcx.sess,
+                        it.span,
+                        E0439,
+                        "invalid `simd_shuffle`, needs length: `{}`",
+                        name
+                    )
+                    .emit();
+                    return;
+                }
             }
-            Err(_) => {
-                struct_span_err!(
-                    tcx.sess,
-                    it.span,
-                    E0439,
-                    "invalid `simd_shuffle`, needs length: `{}`",
-                    name
-                )
-                .emit();
-                return;
-            }
-        },
+        }
         _ => {
             let msg = format!("unrecognized platform-specific intrinsic function: `{}`", name);
             tcx.sess.struct_span_err(it.span, &msg).emit();

src/librustc_typeck/check/method/suggest.rs

@@ -17,7 +17,7 @@ use rustc_middle::ty::print::with_crate_prefix;
 use rustc_middle::ty::{
     self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness,
 };
-use rustc_span::symbol::{kw, Ident};
+use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{source_map, FileName, Span};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use rustc_trait_selection::traits::Obligation;
@@ -743,7 +743,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 let mut fallback_span = true;
                 let msg = "remove this method call";
-                if item_name.as_str() == "as_str" && actual.peel_refs().is_str() {
+                if item_name.name == sym::as_str && actual.peel_refs().is_str() {
                     if let SelfSource::MethodCall(expr) = source {
                         let call_expr =
                             self.tcx.hir().expect_expr(self.tcx.hir().get_parent_node(expr.hir_id));

src/librustc_typeck/check/op.rs

@@ -13,7 +13,7 @@ use rustc_middle::ty::TyKind::{Adt, Array, Char, FnDef, Never, Ref, Str, Tuple,
 use rustc_middle::ty::{
     self, suggest_constraining_type_param, Ty, TyCtxt, TypeFoldable, TypeVisitor,
 };
-use rustc_span::symbol::Ident;
+use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 use rustc_trait_selection::infer::InferCtxtExt;
 
@@ -702,16 +702,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
         let (opname, trait_did) = if let Op::Binary(op, IsAssign::Yes) = op {
             match op.node {
-                hir::BinOpKind::Add => ("add_assign", lang.add_assign_trait()),
-                hir::BinOpKind::Sub => ("sub_assign", lang.sub_assign_trait()),
-                hir::BinOpKind::Mul => ("mul_assign", lang.mul_assign_trait()),
-                hir::BinOpKind::Div => ("div_assign", lang.div_assign_trait()),
-                hir::BinOpKind::Rem => ("rem_assign", lang.rem_assign_trait()),
-                hir::BinOpKind::BitXor => ("bitxor_assign", lang.bitxor_assign_trait()),
-                hir::BinOpKind::BitAnd => ("bitand_assign", lang.bitand_assign_trait()),
-                hir::BinOpKind::BitOr => ("bitor_assign", lang.bitor_assign_trait()),
-                hir::BinOpKind::Shl => ("shl_assign", lang.shl_assign_trait()),
-                hir::BinOpKind::Shr => ("shr_assign", lang.shr_assign_trait()),
+                hir::BinOpKind::Add => (sym::add_assign, lang.add_assign_trait()),
+                hir::BinOpKind::Sub => (sym::sub_assign, lang.sub_assign_trait()),
+                hir::BinOpKind::Mul => (sym::mul_assign, lang.mul_assign_trait()),
+                hir::BinOpKind::Div => (sym::div_assign, lang.div_assign_trait()),
+                hir::BinOpKind::Rem => (sym::rem_assign, lang.rem_assign_trait()),
+                hir::BinOpKind::BitXor => (sym::bitxor_assign, lang.bitxor_assign_trait()),
+                hir::BinOpKind::BitAnd => (sym::bitand_assign, lang.bitand_assign_trait()),
+                hir::BinOpKind::BitOr => (sym::bitor_assign, lang.bitor_assign_trait()),
+                hir::BinOpKind::Shl => (sym::shl_assign, lang.shl_assign_trait()),
+                hir::BinOpKind::Shr => (sym::shr_assign, lang.shr_assign_trait()),
                 hir::BinOpKind::Lt
                 | hir::BinOpKind::Le
                 | hir::BinOpKind::Ge
@@ -725,30 +725,30 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         } else if let Op::Binary(op, IsAssign::No) = op {
             match op.node {
-                hir::BinOpKind::Add => ("add", lang.add_trait()),
-                hir::BinOpKind::Sub => ("sub", lang.sub_trait()),
-                hir::BinOpKind::Mul => ("mul", lang.mul_trait()),
-                hir::BinOpKind::Div => ("div", lang.div_trait()),
-                hir::BinOpKind::Rem => ("rem", lang.rem_trait()),
-                hir::BinOpKind::BitXor => ("bitxor", lang.bitxor_trait()),
-                hir::BinOpKind::BitAnd => ("bitand", lang.bitand_trait()),
-                hir::BinOpKind::BitOr => ("bitor", lang.bitor_trait()),
-                hir::BinOpKind::Shl => ("shl", lang.shl_trait()),
-                hir::BinOpKind::Shr => ("shr", lang.shr_trait()),
-                hir::BinOpKind::Lt => ("lt", lang.partial_ord_trait()),
-                hir::BinOpKind::Le => ("le", lang.partial_ord_trait()),
-                hir::BinOpKind::Ge => ("ge", lang.partial_ord_trait()),
-                hir::BinOpKind::Gt => ("gt", lang.partial_ord_trait()),
-                hir::BinOpKind::Eq => ("eq", lang.eq_trait()),
-                hir::BinOpKind::Ne => ("ne", lang.eq_trait()),
+                hir::BinOpKind::Add => (sym::add, lang.add_trait()),
+                hir::BinOpKind::Sub => (sym::sub, lang.sub_trait()),
+                hir::BinOpKind::Mul => (sym::mul, lang.mul_trait()),
+                hir::BinOpKind::Div => (sym::div, lang.div_trait()),
+                hir::BinOpKind::Rem => (sym::rem, lang.rem_trait()),
+                hir::BinOpKind::BitXor => (sym::bitxor, lang.bitxor_trait()),
+                hir::BinOpKind::BitAnd => (sym::bitand, lang.bitand_trait()),
+                hir::BinOpKind::BitOr => (sym::bitor, lang.bitor_trait()),
+                hir::BinOpKind::Shl => (sym::shl, lang.shl_trait()),
+                hir::BinOpKind::Shr => (sym::shr, lang.shr_trait()),
+                hir::BinOpKind::Lt => (sym::lt, lang.partial_ord_trait()),
+                hir::BinOpKind::Le => (sym::le, lang.partial_ord_trait()),
+                hir::BinOpKind::Ge => (sym::ge, lang.partial_ord_trait()),
+                hir::BinOpKind::Gt => (sym::gt, lang.partial_ord_trait()),
+                hir::BinOpKind::Eq => (sym::eq, lang.eq_trait()),
+                hir::BinOpKind::Ne => (sym::ne, lang.eq_trait()),
                 hir::BinOpKind::And | hir::BinOpKind::Or => {
                     span_bug!(span, "&& and || are not overloadable")
                 }
             }
         } else if let Op::Unary(hir::UnOp::UnNot, _) = op {
-            ("not", lang.not_trait())
+            (sym::not, lang.not_trait())
         } else if let Op::Unary(hir::UnOp::UnNeg, _) = op {
-            ("neg", lang.neg_trait())
+            (sym::neg, lang.neg_trait())
         } else {
             bug!("lookup_op_method: op not supported: {:?}", op)
         };
@@ -759,7 +759,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         );
 
         let method = trait_did.and_then(|trait_did| {
-            let opname = Ident::from_str(opname);
+            let opname = Ident::with_dummy_span(opname);
             self.lookup_method_in_trait(span, opname, trait_did, lhs_ty, Some(other_tys))
         });
 

src/librustdoc/clean/cfg.rs

@@ -162,8 +162,8 @@ impl Cfg {
             Cfg::Any(ref sub_cfgs) | Cfg::All(ref sub_cfgs) => {
                 sub_cfgs.first().map(Cfg::should_capitalize_first_letter).unwrap_or(false)
             }
-            Cfg::Cfg(name, _) => match &*name.as_str() {
-                "debug_assertions" | "target_endian" => true,
+            Cfg::Cfg(name, _) => match name {
+                sym::debug_assertions | sym::target_endian => true,
                 _ => false,
             },
         }
@@ -347,12 +347,11 @@ impl<'a> fmt::Display for Html<'a> {
             Cfg::False => fmt.write_str("nowhere"),
 
             Cfg::Cfg(name, value) => {
-                let n = &*name.as_str();
-                let human_readable = match (n, value) {
-                    ("unix", None) => "Unix",
-                    ("windows", None) => "Windows",
-                    ("debug_assertions", None) => "debug-assertions enabled",
-                    ("target_os", Some(os)) => match &*os.as_str() {
+                let human_readable = match (name, value) {
+                    (sym::unix, None) => "Unix",
+                    (sym::windows, None) => "Windows",
+                    (sym::debug_assertions, None) => "debug-assertions enabled",
+                    (sym::target_os, Some(os)) => match &*os.as_str() {
                         "android" => "Android",
                         "dragonfly" => "DragonFly BSD",
                         "emscripten" => "Emscripten",
@@ -372,7 +371,7 @@ impl<'a> fmt::Display for Html<'a> {
                         "windows" => "Windows",
                         _ => "",
                     },
-                    ("target_arch", Some(arch)) => match &*arch.as_str() {
+                    (sym::target_arch, Some(arch)) => match &*arch.as_str() {
                         "aarch64" => "AArch64",
                         "arm" => "ARM",
                         "asmjs" => "JavaScript",
@@ -388,7 +387,7 @@ impl<'a> fmt::Display for Html<'a> {
                         "x86_64" => "x86-64",
                         _ => "",
                     },
-                    ("target_vendor", Some(vendor)) => match &*vendor.as_str() {
+                    (sym::target_vendor, Some(vendor)) => match &*vendor.as_str() {
                         "apple" => "Apple",
                         "pc" => "PC",
                         "rumprun" => "Rumprun",
@@ -396,7 +395,7 @@ impl<'a> fmt::Display for Html<'a> {
                         "fortanix" => "Fortanix",
                         _ => "",
                     },
-                    ("target_env", Some(env)) => match &*env.as_str() {
+                    (sym::target_env, Some(env)) => match &*env.as_str() {
                         "gnu" => "GNU",
                         "msvc" => "MSVC",
                         "musl" => "musl",
@@ -405,9 +404,9 @@ impl<'a> fmt::Display for Html<'a> {
                         "sgx" => "SGX",
                         _ => "",
                     },
-                    ("target_endian", Some(endian)) => return write!(fmt, "{}-endian", endian),
-                    ("target_pointer_width", Some(bits)) => return write!(fmt, "{}-bit", bits),
-                    ("target_feature", Some(feat)) => {
+                    (sym::target_endian, Some(endian)) => return write!(fmt, "{}-endian", endian),
+                    (sym::target_pointer_width, Some(bits)) => return write!(fmt, "{}-bit", bits),
+                    (sym::target_feature, Some(feat)) => {
                         if self.1 {
                             return write!(fmt, "<code>{}</code>", feat);
                         } else {
@@ -419,9 +418,14 @@ impl<'a> fmt::Display for Html<'a> {
                 if !human_readable.is_empty() {
                     fmt.write_str(human_readable)
                 } else if let Some(v) = value {
-                    write!(fmt, "<code>{}=\"{}\"</code>", Escape(n), Escape(&v.as_str()))
+                    write!(
+                        fmt,
+                        "<code>{}=\"{}\"</code>",
+                        Escape(&name.as_str()),
+                        Escape(&v.as_str())
+                    )
                 } else {
-                    write!(fmt, "<code>{}</code>", Escape(n))
+                    write!(fmt, "<code>{}</code>", Escape(&name.as_str()))
                 }
             }
         }

src/librustdoc/clean/mod.rs

@@ -114,7 +114,7 @@ impl Clean<ExternalCrate> for CrateNum {
                 for attr in attrs.lists(sym::doc) {
                     if let Some(v) = attr.value_str() {
                         if attr.check_name(sym::primitive) {
-                            prim = PrimitiveType::from_str(&v.as_str());
+                            prim = PrimitiveType::from_symbol(v);
                             if prim.is_some() {
                                 break;
                             }

src/librustdoc/clean/types.rs

@@ -21,7 +21,7 @@ use rustc_index::vec::IndexVec;
 use rustc_middle::middle::stability;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::source_map::DUMMY_SP;
-use rustc_span::symbol::{sym, Ident, Symbol};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{self, FileName};
 use rustc_target::abi::VariantIdx;
 use rustc_target::spec::abi::Abi;
@@ -1230,33 +1230,33 @@ impl GetDefId for Type {
 }
 
 impl PrimitiveType {
-    pub fn from_str(s: &str) -> Option<PrimitiveType> {
+    pub fn from_symbol(s: Symbol) -> Option<PrimitiveType> {
         match s {
-            "isize" => Some(PrimitiveType::Isize),
-            "i8" => Some(PrimitiveType::I8),
-            "i16" => Some(PrimitiveType::I16),
-            "i32" => Some(PrimitiveType::I32),
-            "i64" => Some(PrimitiveType::I64),
-            "i128" => Some(PrimitiveType::I128),
-            "usize" => Some(PrimitiveType::Usize),
-            "u8" => Some(PrimitiveType::U8),
-            "u16" => Some(PrimitiveType::U16),
-            "u32" => Some(PrimitiveType::U32),
-            "u64" => Some(PrimitiveType::U64),
-            "u128" => Some(PrimitiveType::U128),
-            "bool" => Some(PrimitiveType::Bool),
-            "char" => Some(PrimitiveType::Char),
-            "str" => Some(PrimitiveType::Str),
-            "f32" => Some(PrimitiveType::F32),
-            "f64" => Some(PrimitiveType::F64),
-            "array" => Some(PrimitiveType::Array),
-            "slice" => Some(PrimitiveType::Slice),
-            "tuple" => Some(PrimitiveType::Tuple),
-            "unit" => Some(PrimitiveType::Unit),
-            "pointer" => Some(PrimitiveType::RawPointer),
-            "reference" => Some(PrimitiveType::Reference),
-            "fn" => Some(PrimitiveType::Fn),
-            "never" => Some(PrimitiveType::Never),
+            sym::isize => Some(PrimitiveType::Isize),
+            sym::i8 => Some(PrimitiveType::I8),
+            sym::i16 => Some(PrimitiveType::I16),
+            sym::i32 => Some(PrimitiveType::I32),
+            sym::i64 => Some(PrimitiveType::I64),
+            sym::i128 => Some(PrimitiveType::I128),
+            sym::usize => Some(PrimitiveType::Usize),
+            sym::u8 => Some(PrimitiveType::U8),
+            sym::u16 => Some(PrimitiveType::U16),
+            sym::u32 => Some(PrimitiveType::U32),
+            sym::u64 => Some(PrimitiveType::U64),
+            sym::u128 => Some(PrimitiveType::U128),
+            sym::bool => Some(PrimitiveType::Bool),
+            sym::char => Some(PrimitiveType::Char),
+            sym::str => Some(PrimitiveType::Str),
+            sym::f32 => Some(PrimitiveType::F32),
+            sym::f64 => Some(PrimitiveType::F64),
+            sym::array => Some(PrimitiveType::Array),
+            sym::slice => Some(PrimitiveType::Slice),
+            sym::tuple => Some(PrimitiveType::Tuple),
+            sym::unit => Some(PrimitiveType::Unit),
+            sym::pointer => Some(PrimitiveType::RawPointer),
+            sym::reference => Some(PrimitiveType::Reference),
+            kw::Fn => Some(PrimitiveType::Fn),
+            sym::never => Some(PrimitiveType::Never),
             _ => None,
         }
     }

src/test/ui/hygiene/unpretty-debug.stdout

@@ -10,7 +10,10 @@
 
 macro_rules! foo /* 0#0 */ { ($ x : ident) => { y + $ x } }
 
-fn bar /* 0#0 */() { let x /* 0#0 */ = 1; y /* 0#1 */ + x /* 0#0 */ }
+fn bar /* 0#0 */() {
+    let x /* 0#0 */ = 1;
+    y /* 0#1 */ + x /* 0#0 */
+}
 
 fn y /* 0#0 */() { }