Rollup merge of #30590 - nagisa:mir-constval-function, r=luqmana

This moves back (essentially reverts #30265) into MIR-specific translation code, but keeps the
funcition split out, since it is expected to eventually become recursive.

Fixes https://github.com/rust-lang/rust/issues/29572

cc @oli-obk

src/librustc_trans/trans/consts.rs

@@ -31,7 +31,6 @@ use trans::{adt, closure, debuginfo, expr, inline, machine};
 use trans::base::{self, push_ctxt};
 use trans::common::{self, type_is_sized, ExprOrMethodCall, node_id_substs, C_nil, const_get_elt};
 use trans::common::{CrateContext, C_integral, C_floating, C_bool, C_str_slice, C_bytes, val_ty};
-use trans::common::C_floating_f64;
 use trans::common::{C_struct, C_undef, const_to_opt_int, const_to_opt_uint, VariantInfo, C_uint};
 use trans::common::{type_is_fat_ptr, Field, C_vector, C_array, C_null, ExprId, MethodCallKey};
 use trans::declare;
@@ -108,38 +107,6 @@ pub fn const_lit(cx: &CrateContext, e: &hir::Expr, lit: &ast::Lit)
     }
 }
 
-pub fn trans_constval<'blk, 'tcx>(bcx: common::Block<'blk, 'tcx>,
-                                cv: &ConstVal,
-                                ty: Ty<'tcx>,
-                                param_substs: &'tcx Substs<'tcx>)
-                                -> ValueRef
-{
-    let ccx = bcx.ccx();
-    let llty = type_of::type_of(ccx, ty);
-    match *cv {
-        ConstVal::Float(v) => C_floating_f64(v, llty),
-        ConstVal::Bool(v) => C_bool(ccx, v),
-        ConstVal::Int(v) => C_integral(llty, v as u64, true),
-        ConstVal::Uint(v) => C_integral(llty, v, false),
-        ConstVal::Str(ref v) => C_str_slice(ccx, v.clone()),
-        ConstVal::ByteStr(ref v) => addr_of(ccx, C_bytes(ccx, v), 1, "byte_str"),
-        ConstVal::Struct(id) | ConstVal::Tuple(id) => {
-            let expr = bcx.tcx().map.expect_expr(id);
-            match const_expr(ccx, expr, param_substs, None, TrueConst::Yes) {
-                Ok((val, _)) => val,
-                Err(e) => panic!("const eval failure: {}", e.description()),
-            }
-        },
-        ConstVal::Array(id, _) | ConstVal::Repeat(id, _) => {
-            let expr = bcx.tcx().map.expect_expr(id);
-            expr::trans(bcx, expr).datum.val
-        },
-        ConstVal::Function(_) => {
-            unimplemented!()
-        },
-    }
-}
-
 pub fn ptrcast(val: ValueRef, ty: Type) -> ValueRef {
     unsafe {
         llvm::LLVMConstPointerCast(val, ty.to_ref())

src/librustc_trans/trans/mir/constant.rs

@@ -9,11 +9,14 @@
 // except according to those terms.
 
 use back::abi;
+use llvm::ValueRef;
+use middle::subst::Substs;
 use middle::ty::{Ty, HasTypeFlags};
 use rustc::middle::const_eval::ConstVal;
 use rustc::mir::repr as mir;
-use trans::consts;
-use trans::common::{self, Block};
+use trans::common::{self, Block, C_bool, C_bytes, C_floating_f64, C_integral, C_str_slice};
+use trans::consts::{self, TrueConst};
+use trans::{type_of, expr};
 
 
 use super::operand::{OperandRef, OperandValue};
@@ -27,7 +30,7 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
                           -> OperandRef<'tcx>
     {
         let ccx = bcx.ccx();
-        let val = consts::trans_constval(bcx, cv, ty, bcx.fcx.param_substs);
+        let val = self.trans_constval_inner(bcx, cv, ty, bcx.fcx.param_substs);
         let val = if common::type_is_immediate(ccx, ty) {
             OperandValue::Immediate(val)
         } else if common::type_is_fat_ptr(bcx.tcx(), ty) {
@@ -46,6 +49,39 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
         }
     }
 
+    /// Translate ConstVal into a bare LLVM ValueRef.
+    fn trans_constval_inner(&mut self,
+                            bcx: common::Block<'bcx, 'tcx>,
+                            cv: &ConstVal,
+                            ty: Ty<'tcx>,
+                            param_substs: &'tcx Substs<'tcx>)
+                            -> ValueRef
+    {
+        let ccx = bcx.ccx();
+        let llty = type_of::type_of(ccx, ty);
+        match *cv {
+            ConstVal::Float(v) => C_floating_f64(v, llty),
+            ConstVal::Bool(v) => C_bool(ccx, v),
+            ConstVal::Int(v) => C_integral(llty, v as u64, true),
+            ConstVal::Uint(v) => C_integral(llty, v, false),
+            ConstVal::Str(ref v) => C_str_slice(ccx, v.clone()),
+            ConstVal::ByteStr(ref v) => consts::addr_of(ccx, C_bytes(ccx, v), 1, "byte_str"),
+            ConstVal::Struct(id) | ConstVal::Tuple(id) => {
+                let expr = bcx.tcx().map.expect_expr(id);
+                match consts::const_expr(ccx, expr, param_substs, None, TrueConst::Yes) {
+                    Ok((val, _)) => val,
+                    Err(e) => panic!("const eval failure: {}", e.description()),
+                }
+            },
+            ConstVal::Array(id, _) | ConstVal::Repeat(id, _) => {
+                let expr = bcx.tcx().map.expect_expr(id);
+                expr::trans(bcx, expr).datum.val
+            },
+            ConstVal::Function(did) =>
+                self.trans_fn_ref(bcx, ty, param_substs, did).immediate()
+        }
+    }
+
     pub fn trans_constant(&mut self,
                           bcx: Block<'bcx, 'tcx>,
                           constant: &mir::Constant<'tcx>)

src/test/run-pass/mir_refs_correct.rs

@@ -68,6 +68,7 @@ enum CEnum {
 const C: u8 = 84;
 const C2: [u8; 5] = [42; 5];
 const C3: [u8; 3] = [42, 41, 40];
+const C4: fn(u8) -> S = S;
 
 fn regular() -> u8 {
     21
@@ -198,6 +199,11 @@ fn t23() -> (CEnum, CEnum) {
     (CEnum::A, CEnum::B)
 }
 
+#[rustc_mir]
+fn t24() -> fn(u8) -> S {
+    C4
+}
+
 fn main(){
     unsafe {
         assert_eq!(t1()(), regular());
@@ -240,5 +246,6 @@ fn main(){
         assert_eq!(t21(), Unit);
         assert_eq!(t22(), None);
         assert_eq!(t23(), (CEnum::A, CEnum::B));
+        assert_eq!(t24(), C4);
     }
 }