Replace ByVal attribute with on_stack field for Indirect

This makes it clearer that only PassMode::Indirect allows ByVal

compiler/rustc_codegen_llvm/src/abi.rs

@@ -41,12 +41,12 @@ impl ArgAttributeExt for ArgAttribute {
 }
 
 pub trait ArgAttributesExt {
-    fn apply_llfn(&self, idx: AttributePlace, llfn: &Value, ty: Option<&Type>);
-    fn apply_callsite(&self, idx: AttributePlace, callsite: &Value, ty: Option<&Type>);
+    fn apply_attrs_to_llfn(&self, idx: AttributePlace, llfn: &Value);
+    fn apply_attrs_to_callsite(&self, idx: AttributePlace, callsite: &Value);
 }
 
 impl ArgAttributesExt for ArgAttributes {
-    fn apply_llfn(&self, idx: AttributePlace, llfn: &Value, ty: Option<&Type>) {
+    fn apply_attrs_to_llfn(&self, idx: AttributePlace, llfn: &Value) {
         let mut regular = self.regular;
         unsafe {
             let deref = self.pointee_size.bytes();
@@ -61,9 +61,6 @@ impl ArgAttributesExt for ArgAttributes {
             if let Some(align) = self.pointee_align {
                 llvm::LLVMRustAddAlignmentAttr(llfn, idx.as_uint(), align.bytes() as u32);
             }
-            if regular.contains(ArgAttribute::ByVal) {
-                llvm::LLVMRustAddByValAttr(llfn, idx.as_uint(), ty.unwrap());
-            }
             regular.for_each_kind(|attr| attr.apply_llfn(idx, llfn));
             match self.arg_ext {
                 ArgExtension::None => {}
@@ -77,7 +74,7 @@ impl ArgAttributesExt for ArgAttributes {
         }
     }
 
-    fn apply_callsite(&self, idx: AttributePlace, callsite: &Value, ty: Option<&Type>) {
+    fn apply_attrs_to_callsite(&self, idx: AttributePlace, callsite: &Value) {
         let mut regular = self.regular;
         unsafe {
             let deref = self.pointee_size.bytes();
@@ -100,9 +97,6 @@ impl ArgAttributesExt for ArgAttributes {
                     align.bytes() as u32,
                 );
             }
-            if regular.contains(ArgAttribute::ByVal) {
-                llvm::LLVMRustAddByValCallSiteAttr(callsite, idx.as_uint(), ty.unwrap());
-            }
             regular.for_each_kind(|attr| attr.apply_callsite(idx, callsite));
             match self.arg_ext {
                 ArgExtension::None => {}
@@ -285,10 +279,12 @@ impl ArgAbiExt<'ll, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
             PassMode::Pair(..) => {
                 OperandValue::Pair(next(), next()).store(bx, dst);
             }
-            PassMode::Indirect(_, Some(_)) => {
+            PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ } => {
                 OperandValue::Ref(next(), Some(next()), self.layout.align.abi).store(bx, dst);
             }
-            PassMode::Direct(_) | PassMode::Indirect(_, None) | PassMode::Cast(_) => {
+            PassMode::Direct(_)
+            | PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ }
+            | PassMode::Cast(_) => {
                 let next_arg = next();
                 self.store(bx, next_arg, dst);
             }
@@ -333,14 +329,14 @@ impl<'tcx> FnAbiLlvmExt<'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             if let PassMode::Pair(_, _) = arg.mode { 2 } else { 1 }
         ).sum();
         let mut llargument_tys = Vec::with_capacity(
-            if let PassMode::Indirect(..) = self.ret.mode { 1 } else { 0 } + args_capacity,
+            if let PassMode::Indirect { .. } = self.ret.mode { 1 } else { 0 } + args_capacity,
         );
 
         let llreturn_ty = match self.ret.mode {
             PassMode::Ignore => cx.type_void(),
             PassMode::Direct(_) | PassMode::Pair(..) => self.ret.layout.immediate_llvm_type(cx),
             PassMode::Cast(cast) => cast.llvm_type(cx),
-            PassMode::Indirect(..) => {
+            PassMode::Indirect { .. } => {
                 llargument_tys.push(cx.type_ptr_to(self.ret.memory_ty(cx)));
                 cx.type_void()
             }
@@ -360,7 +356,7 @@ impl<'tcx> FnAbiLlvmExt<'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                     llargument_tys.push(arg.layout.scalar_pair_element_llvm_type(cx, 1, true));
                     continue;
                 }
-                PassMode::Indirect(_, Some(_)) => {
+                PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ } => {
                     let ptr_ty = cx.tcx.mk_mut_ptr(arg.layout.ty);
                     let ptr_layout = cx.layout_of(ptr_ty);
                     llargument_tys.push(ptr_layout.scalar_pair_element_llvm_type(cx, 0, true));
@@ -368,7 +364,9 @@ impl<'tcx> FnAbiLlvmExt<'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                     continue;
                 }
                 PassMode::Cast(cast) => cast.llvm_type(cx),
-                PassMode::Indirect(_, None) => cx.type_ptr_to(arg.memory_ty(cx)),
+                PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ } => {
+                    cx.type_ptr_to(arg.memory_ty(cx))
+                }
             };
             llargument_tys.push(llarg_ty);
         }
@@ -420,35 +418,53 @@ impl<'tcx> FnAbiLlvmExt<'tcx> for FnAbi<'tcx, Ty<'tcx>> {
         }
 
         let mut i = 0;
-        let mut apply = |attrs: &ArgAttributes, ty: Option<&Type>| {
-            attrs.apply_llfn(llvm::AttributePlace::Argument(i), llfn, ty);
+        let mut apply = |attrs: &ArgAttributes| {
+            attrs.apply_attrs_to_llfn(llvm::AttributePlace::Argument(i), llfn);
             i += 1;
+            i - 1
         };
         match self.ret.mode {
             PassMode::Direct(ref attrs) => {
-                attrs.apply_llfn(llvm::AttributePlace::ReturnValue, llfn, None);
+                attrs.apply_attrs_to_llfn(llvm::AttributePlace::ReturnValue, llfn);
+            }
+            PassMode::Indirect { ref attrs, extra_attrs: _, on_stack } => {
+                assert!(!on_stack);
+                apply(attrs);
             }
-            PassMode::Indirect(ref attrs, _) => apply(attrs, Some(self.ret.layout.llvm_type(cx))),
             _ => {}
         }
         for arg in &self.args {
             if arg.pad.is_some() {
-                apply(&ArgAttributes::new(), None);
+                apply(&ArgAttributes::new());
             }
             match arg.mode {
                 PassMode::Ignore => {}
-                PassMode::Direct(ref attrs) | PassMode::Indirect(ref attrs, None) => {
-                    apply(attrs, Some(arg.layout.llvm_type(cx)))
+                PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: true } => {
+                    let i = apply(attrs);
+                    unsafe {
+                        llvm::LLVMRustAddByValAttr(
+                            llfn,
+                            llvm::AttributePlace::Argument(i).as_uint(),
+                            arg.layout.llvm_type(cx),
+                        );
                     }
-                PassMode::Indirect(ref attrs, Some(ref extra_attrs)) => {
-                    apply(attrs, None);
-                    apply(extra_attrs, None);
+                }
+                PassMode::Direct(ref attrs)
+                | PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: false } => {
+                    apply(attrs);
+                }
+                PassMode::Indirect { ref attrs, extra_attrs: Some(ref extra_attrs), on_stack } => {
+                    assert!(!on_stack);
+                    apply(attrs);
+                    apply(extra_attrs);
                 }
                 PassMode::Pair(ref a, ref b) => {
-                    apply(a, None);
-                    apply(b, None);
+                    apply(a);
+                    apply(b);
+                }
+                PassMode::Cast(_) => {
+                    apply(&ArgAttributes::new());
                 }
-                PassMode::Cast(_) => apply(&ArgAttributes::new(), None),
             }
         }
     }
@@ -457,15 +473,19 @@ impl<'tcx> FnAbiLlvmExt<'tcx> for FnAbi<'tcx, Ty<'tcx>> {
         // FIXME(wesleywiser, eddyb): We should apply `nounwind` and `noreturn` as appropriate to this callsite.
 
         let mut i = 0;
-        let mut apply = |attrs: &ArgAttributes, ty: Option<&Type>| {
-            attrs.apply_callsite(llvm::AttributePlace::Argument(i), callsite, ty);
+        let mut apply = |attrs: &ArgAttributes| {
+            attrs.apply_attrs_to_callsite(llvm::AttributePlace::Argument(i), callsite);
             i += 1;
+            i - 1
         };
         match self.ret.mode {
             PassMode::Direct(ref attrs) => {
-                attrs.apply_callsite(llvm::AttributePlace::ReturnValue, callsite, None);
+                attrs.apply_attrs_to_callsite(llvm::AttributePlace::ReturnValue, callsite);
+            }
+            PassMode::Indirect { ref attrs, extra_attrs: _, on_stack } => {
+                assert!(!on_stack);
+                apply(attrs);
             }
-            PassMode::Indirect(ref attrs, _) => apply(attrs, Some(self.ret.layout.llvm_type(bx))),
             _ => {}
         }
         if let abi::Abi::Scalar(ref scalar) = self.ret.layout.abi {
@@ -483,22 +503,39 @@ impl<'tcx> FnAbiLlvmExt<'tcx> for FnAbi<'tcx, Ty<'tcx>> {
         }
         for arg in &self.args {
             if arg.pad.is_some() {
-                apply(&ArgAttributes::new(), None);
+                apply(&ArgAttributes::new());
             }
             match arg.mode {
                 PassMode::Ignore => {}
-                PassMode::Direct(ref attrs) | PassMode::Indirect(ref attrs, None) => {
-                    apply(attrs, Some(arg.layout.llvm_type(bx)))
+                PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: true } => {
+                    let i = apply(attrs);
+                    unsafe {
+                        llvm::LLVMRustAddByValCallSiteAttr(
+                            callsite,
+                            llvm::AttributePlace::Argument(i).as_uint(),
+                            arg.layout.llvm_type(bx),
+                        );
                     }
-                PassMode::Indirect(ref attrs, Some(ref extra_attrs)) => {
-                    apply(attrs, None);
-                    apply(extra_attrs, None);
+                }
+                PassMode::Direct(ref attrs)
+                | PassMode::Indirect { ref attrs, extra_attrs: None, on_stack: false } => {
+                    apply(attrs);
+                }
+                PassMode::Indirect {
+                    ref attrs,
+                    extra_attrs: Some(ref extra_attrs),
+                    on_stack: _,
+                } => {
+                    apply(attrs);
+                    apply(extra_attrs);
                 }
                 PassMode::Pair(ref a, ref b) => {
-                    apply(a, None);
-                    apply(b, None);
+                    apply(a);
+                    apply(b);
+                }
+                PassMode::Cast(_) => {
+                    apply(&ArgAttributes::new());
                 }
-                PassMode::Cast(_) => apply(&ArgAttributes::new(), None),
             }
         }
 

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -255,7 +255,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             return;
         }
         let llval = match self.fn_abi.ret.mode {
-            PassMode::Ignore | PassMode::Indirect(..) => {
+            PassMode::Ignore | PassMode::Indirect { .. } => {
                 bx.ret_void();
                 return;
             }
@@ -1101,7 +1101,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // Force by-ref if we have to load through a cast pointer.
         let (mut llval, align, by_ref) = match op.val {
             Immediate(_) | Pair(..) => match arg.mode {
-                PassMode::Indirect(..) | PassMode::Cast(_) => {
+                PassMode::Indirect { .. } | PassMode::Cast(_) => {
                     let scratch = PlaceRef::alloca(bx, arg.layout);
                     op.val.store(bx, scratch);
                     (scratch.llval, scratch.align, true)

compiler/rustc_middle/src/ty/layout.rs

@@ -2801,7 +2801,8 @@ where
             for arg in &mut self.args {
                 fixup(arg, false);
             }
-            if let PassMode::Indirect(ref mut attrs, _) = self.ret.mode {
+            if let PassMode::Indirect { ref mut attrs, extra_attrs: _, on_stack: _ } = self.ret.mode
+            {
                 attrs.set(ArgAttribute::StructRet);
             }
             return;

compiler/rustc_target/src/abi/call/mod.rs

@@ -36,9 +36,12 @@ pub enum PassMode {
     /// a single uniform or a pair of registers.
     Cast(CastTarget),
     /// Pass the argument indirectly via a hidden pointer.
-    /// The second value, if any, is for the extra data (vtable or length)
+    /// The `extra_attrs` value, if any, is for the extra data (vtable or length)
     /// which indicates that it refers to an unsized rvalue.
-    Indirect(ArgAttributes, Option<ArgAttributes>),
+    /// `on_stack` defines that the the value should be passed at a fixed
+    /// stack offset in accordance to the ABI rather than passed using a
+    /// pointer. This corresponds to the `byval` LLVM argument attribute.
+    Indirect { attrs: ArgAttributes, extra_attrs: Option<ArgAttributes>, on_stack: bool },
 }
 
 // Hack to disable non_upper_case_globals only for the bitflags! and not for the rest
@@ -52,7 +55,6 @@ mod attr_impl {
     bitflags::bitflags! {
         #[derive(Default)]
         pub struct ArgAttribute: u16 {
-            const ByVal     = 1 << 0;
             const NoAlias   = 1 << 1;
             const NoCapture = 1 << 2;
             const NonNull   = 1 << 3;
@@ -460,14 +462,14 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
 
         let extra_attrs = self.layout.is_unsized().then_some(ArgAttributes::new());
 
-        self.mode = PassMode::Indirect(attrs, extra_attrs);
+        self.mode = PassMode::Indirect { attrs, extra_attrs, on_stack: false };
     }
 
     pub fn make_indirect_byval(&mut self) {
         self.make_indirect();
         match self.mode {
-            PassMode::Indirect(ref mut attrs, _) => {
-                attrs.set(ArgAttribute::ByVal);
+            PassMode::Indirect { attrs: _, extra_attrs: _, ref mut on_stack } => {
+                *on_stack = true;
             }
             _ => unreachable!(),
         }
@@ -500,15 +502,15 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
     }
 
     pub fn is_indirect(&self) -> bool {
-        matches!(self.mode, PassMode::Indirect(..))
+        matches!(self.mode, PassMode::Indirect {..})
     }
 
     pub fn is_sized_indirect(&self) -> bool {
-        matches!(self.mode, PassMode::Indirect(_, None))
+        matches!(self.mode, PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ })
     }
 
     pub fn is_unsized_indirect(&self) -> bool {
-        matches!(self.mode, PassMode::Indirect(_, Some(_)))
+        matches!(self.mode, PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ })
     }
 
     pub fn is_ignore(&self) -> bool {
@@ -617,7 +619,7 @@ impl<'a, Ty> FnAbi<'a, Ty> {
             a => return Err(format!("unrecognized arch \"{}\" in target specification", a)),
         }
 
-        if let PassMode::Indirect(ref mut attrs, _) = self.ret.mode {
+        if let PassMode::Indirect { ref mut attrs, extra_attrs: _, on_stack: _ } = self.ret.mode {
             attrs.set(ArgAttribute::StructRet);
         }
 

compiler/rustc_target/src/abi/call/x86.rs

@@ -92,9 +92,14 @@ where
 
         for arg in &mut fn_abi.args {
             let attrs = match arg.mode {
-                PassMode::Ignore | PassMode::Indirect(_, None) => continue,
+                PassMode::Ignore
+                | PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ } => {
+                    continue;
+                }
                 PassMode::Direct(ref mut attrs) => attrs,
-                PassMode::Pair(..) | PassMode::Indirect(_, Some(_)) | PassMode::Cast(_) => {
+                PassMode::Pair(..)
+                | PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ }
+                | PassMode::Cast(_) => {
                     unreachable!("x86 shouldn't be passing arguments by {:?}", arg.mode)
                 }
             };