Auto merge of #122050 - erikdesjardins:sret, r=<try>

Stop using LLVM struct types for byval/sret For `byval`, and `sret`, the type has no semantic meaning, only the size matters\*†. Using `[N x i8]` is a more direct way to specify that we want `N` bytes, and avoids relying on LLVM's struct layout. \*: The alignment would also matter if we didn't explicitly specify it. From what I can tell, we always specified the alignment for `sret`; for `byval`, we didn't until #112157. †: For `byval`, the hidden copy may be impacted by padding in the LLVM struct type, i.e. padding bytes may not be copied. (I'm not sure if this is done today, but I think it would be legal.) But we manually pad our LLVM struct types specifically to avoid there ever being LLVM-visible padding, so that shouldn't be an issue. Split out from #121577. r? `@nikic`
rust-lang · Mar 6, 2024 · d5b8881 · d5b8881
2 parents b6d2d84 + 96a7267
commit d5b8881
Show file tree

Hide file tree

Showing 10 changed files with 80 additions and 73 deletions.
diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -424,7 +424,10 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             PassMode::Indirect { attrs, meta_attrs: _, on_stack } => {
                 assert!(!on_stack);
                 let i = apply(attrs);
-                let sret = llvm::CreateStructRetAttr(cx.llcx, self.ret.layout.llvm_type(cx));
+                let sret = llvm::CreateStructRetAttr(
+                    cx.llcx,
+                    cx.type_array(cx.type_i8(), self.ret.layout.size.bytes()),
+                );
                 attributes::apply_to_llfn(llfn, llvm::AttributePlace::Argument(i), &[sret]);
             }
             PassMode::Cast { cast, pad_i32: _ } => {
@@ -437,7 +440,10 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                 PassMode::Ignore => {}
                 PassMode::Indirect { attrs, meta_attrs: None, on_stack: true } => {
                     let i = apply(attrs);
-                    let byval = llvm::CreateByValAttr(cx.llcx, arg.layout.llvm_type(cx));
+                    let byval = llvm::CreateByValAttr(
+                        cx.llcx,
+                        cx.type_array(cx.type_i8(), arg.layout.size.bytes()),
+                    );
                     attributes::apply_to_llfn(llfn, llvm::AttributePlace::Argument(i), &[byval]);
                 }
                 PassMode::Direct(attrs)
@@ -486,7 +492,10 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             PassMode::Indirect { attrs, meta_attrs: _, on_stack } => {
                 assert!(!on_stack);
                 let i = apply(bx.cx, attrs);
-                let sret = llvm::CreateStructRetAttr(bx.cx.llcx, self.ret.layout.llvm_type(bx));
+                let sret = llvm::CreateStructRetAttr(
+                    bx.cx.llcx,
+                    bx.cx.type_array(bx.cx.type_i8(), self.ret.layout.size.bytes()),
+                );
                 attributes::apply_to_callsite(callsite, llvm::AttributePlace::Argument(i), &[sret]);
             }
             PassMode::Cast { cast, pad_i32: _ } => {
@@ -513,7 +522,10 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                 PassMode::Ignore => {}
                 PassMode::Indirect { attrs, meta_attrs: None, on_stack: true } => {
                     let i = apply(bx.cx, attrs);
-                    let byval = llvm::CreateByValAttr(bx.cx.llcx, arg.layout.llvm_type(bx));
+                    let byval = llvm::CreateByValAttr(
+                        bx.cx.llcx,
+                        bx.cx.type_array(bx.cx.type_i8(), arg.layout.size.bytes()),
+                    );
                     attributes::apply_to_callsite(
                         callsite,
                         llvm::AttributePlace::Argument(i),

diff --git a/tests/codegen/align-byval-vector.rs b/tests/codegen/align-byval-vector.rs
@@ -37,12 +37,12 @@ pub struct DoubleFoo {
 }
 
 extern "C" {
-    // x86-linux: declare void @f({{.*}}byval(%Foo) align 4{{.*}})
-    // x86-darwin: declare void @f({{.*}}byval(%Foo) align 16{{.*}})
+    // x86-linux: declare void @f({{.*}}byval([32 x i8]) align 4{{.*}})
+    // x86-darwin: declare void @f({{.*}}byval([32 x i8]) align 16{{.*}})
     fn f(foo: Foo);
 
-    // x86-linux: declare void @g({{.*}}byval(%DoubleFoo) align 4{{.*}})
-    // x86-darwin: declare void @g({{.*}}byval(%DoubleFoo) align 16{{.*}})
+    // x86-linux: declare void @g({{.*}}byval([64 x i8]) align 4{{.*}})
+    // x86-darwin: declare void @g({{.*}}byval([64 x i8]) align 16{{.*}})
     fn g(foo: DoubleFoo);
 }
 

diff --git a/tests/codegen/align-byval.rs b/tests/codegen/align-byval.rs
@@ -107,20 +107,20 @@ pub unsafe fn call_na1(x: NaturalAlign1) {
     // CHECK: start:
 
     // m68k: [[ALLOCA:%[a-z0-9+]]] = alloca %NaturalAlign1, align 1
-    // m68k: call void @natural_align_1({{.*}}byval(%NaturalAlign1) align 1{{.*}} [[ALLOCA]])
+    // m68k: call void @natural_align_1({{.*}}byval([2 x i8]) align 1{{.*}} [[ALLOCA]])
 
     // wasm: [[ALLOCA:%[a-z0-9+]]] = alloca %NaturalAlign1, align 1
-    // wasm: call void @natural_align_1({{.*}}byval(%NaturalAlign1) align 1{{.*}} [[ALLOCA]])
+    // wasm: call void @natural_align_1({{.*}}byval([2 x i8]) align 1{{.*}} [[ALLOCA]])
 
     // x86_64-linux: call void @natural_align_1(i16
 
     // x86_64-windows: call void @natural_align_1(i16
 
     // i686-linux: [[ALLOCA:%[a-z0-9+]]] = alloca %NaturalAlign1, align 4
-    // i686-linux: call void @natural_align_1({{.*}}byval(%NaturalAlign1) align 4{{.*}} [[ALLOCA]])
+    // i686-linux: call void @natural_align_1({{.*}}byval([2 x i8]) align 4{{.*}} [[ALLOCA]])
 
     // i686-windows: [[ALLOCA:%[a-z0-9+]]] = alloca %NaturalAlign1, align 4
-    // i686-windows: call void @natural_align_1({{.*}}byval(%NaturalAlign1) align 4{{.*}} [[ALLOCA]])
+    // i686-windows: call void @natural_align_1({{.*}}byval([2 x i8]) align 4{{.*}} [[ALLOCA]])
     natural_align_1(x);
 }
 
@@ -135,10 +135,10 @@ pub unsafe fn call_na2(x: NaturalAlign2) {
     // x86_64-windows-NEXT: call void @natural_align_2
 
     // i686-linux: [[ALLOCA:%[0-9]+]] = alloca %NaturalAlign2, align 4
-    // i686-linux: call void @natural_align_2({{.*}}byval(%NaturalAlign2) align 4{{.*}} [[ALLOCA]])
+    // i686-linux: call void @natural_align_2({{.*}}byval([34 x i8]) align 4{{.*}} [[ALLOCA]])
 
     // i686-windows: [[ALLOCA:%[0-9]+]] = alloca %NaturalAlign2, align 4
-    // i686-windows: call void @natural_align_2({{.*}}byval(%NaturalAlign2) align 4{{.*}} [[ALLOCA]])
+    // i686-windows: call void @natural_align_2({{.*}}byval([34 x i8]) align 4{{.*}} [[ALLOCA]])
     natural_align_2(x);
 }
 
@@ -199,141 +199,141 @@ pub unsafe fn call_fa16(x: ForceAlign16) {
 }
 
 extern "C" {
-    // m68k: declare void @natural_align_1({{.*}}byval(%NaturalAlign1) align 1{{.*}})
+    // m68k: declare void @natural_align_1({{.*}}byval([2 x i8]) align 1{{.*}})
 
-    // wasm: declare void @natural_align_1({{.*}}byval(%NaturalAlign1) align 1{{.*}})
+    // wasm: declare void @natural_align_1({{.*}}byval([2 x i8]) align 1{{.*}})
 
     // x86_64-linux: declare void @natural_align_1(i16)
 
     // x86_64-windows: declare void @natural_align_1(i16)
 
-    // i686-linux: declare void @natural_align_1({{.*}}byval(%NaturalAlign1) align 4{{.*}})
+    // i686-linux: declare void @natural_align_1({{.*}}byval([2 x i8]) align 4{{.*}})
 
-    // i686-windows: declare void @natural_align_1({{.*}}byval(%NaturalAlign1) align 4{{.*}})
+    // i686-windows: declare void @natural_align_1({{.*}}byval([2 x i8]) align 4{{.*}})
     fn natural_align_1(x: NaturalAlign1);
 
-    // m68k: declare void @natural_align_2({{.*}}byval(%NaturalAlign2) align 2{{.*}})
+    // m68k: declare void @natural_align_2({{.*}}byval([34 x i8]) align 2{{.*}})
 
-    // wasm: declare void @natural_align_2({{.*}}byval(%NaturalAlign2) align 2{{.*}})
+    // wasm: declare void @natural_align_2({{.*}}byval([34 x i8]) align 2{{.*}})
 
-    // x86_64-linux: declare void @natural_align_2({{.*}}byval(%NaturalAlign2) align 2{{.*}})
+    // x86_64-linux: declare void @natural_align_2({{.*}}byval([34 x i8]) align 2{{.*}})
 
     // x86_64-windows: declare void @natural_align_2(
     // x86_64-windows-NOT: byval
     // x86_64-windows-SAME: align 2{{.*}})
 
-    // i686-linux: declare void @natural_align_2({{.*}}byval(%NaturalAlign2) align 4{{.*}})
+    // i686-linux: declare void @natural_align_2({{.*}}byval([34 x i8]) align 4{{.*}})
 
-    // i686-windows: declare void @natural_align_2({{.*}}byval(%NaturalAlign2) align 4{{.*}})
+    // i686-windows: declare void @natural_align_2({{.*}}byval([34 x i8]) align 4{{.*}})
     fn natural_align_2(x: NaturalAlign2);
 
-    // m68k: declare void @force_align_4({{.*}}byval(%ForceAlign4) align 4{{.*}})
+    // m68k: declare void @force_align_4({{.*}}byval([20 x i8]) align 4{{.*}})
 
-    // wasm: declare void @force_align_4({{.*}}byval(%ForceAlign4) align 4{{.*}})
+    // wasm: declare void @force_align_4({{.*}}byval([20 x i8]) align 4{{.*}})
 
-    // x86_64-linux: declare void @force_align_4({{.*}}byval(%ForceAlign4) align 4{{.*}})
+    // x86_64-linux: declare void @force_align_4({{.*}}byval([20 x i8]) align 4{{.*}})
 
     // x86_64-windows: declare void @force_align_4(
     // x86_64-windows-NOT: byval
     // x86_64-windows-SAME: align 4{{.*}})
 
-    // i686-linux: declare void @force_align_4({{.*}}byval(%ForceAlign4) align 4{{.*}})
+    // i686-linux: declare void @force_align_4({{.*}}byval([20 x i8]) align 4{{.*}})
 
-    // i686-windows: declare void @force_align_4({{.*}}byval(%ForceAlign4) align 4{{.*}})
+    // i686-windows: declare void @force_align_4({{.*}}byval([20 x i8]) align 4{{.*}})
     fn force_align_4(x: ForceAlign4);
 
-    // m68k: declare void @natural_align_8({{.*}}byval(%NaturalAlign8) align 4{{.*}})
+    // m68k: declare void @natural_align_8({{.*}}byval([24 x i8]) align 4{{.*}})
 
-    // wasm: declare void @natural_align_8({{.*}}byval(%NaturalAlign8) align 8{{.*}})
+    // wasm: declare void @natural_align_8({{.*}}byval([24 x i8]) align 8{{.*}})
 
-    // x86_64-linux: declare void @natural_align_8({{.*}}byval(%NaturalAlign8) align 8{{.*}})
+    // x86_64-linux: declare void @natural_align_8({{.*}}byval([24 x i8]) align 8{{.*}})
 
     // x86_64-windows: declare void @natural_align_8(
     // x86_64-windows-NOT: byval
     // x86_64-windows-SAME: align 8{{.*}})
 
-    // i686-linux: declare void @natural_align_8({{.*}}byval(%NaturalAlign8) align 4{{.*}})
+    // i686-linux: declare void @natural_align_8({{.*}}byval([24 x i8]) align 4{{.*}})
 
-    // i686-windows: declare void @natural_align_8({{.*}}byval(%NaturalAlign8) align 4{{.*}})
+    // i686-windows: declare void @natural_align_8({{.*}}byval([24 x i8]) align 4{{.*}})
     fn natural_align_8(x: NaturalAlign8);
 
-    // m68k: declare void @force_align_8({{.*}}byval(%ForceAlign8) align 8{{.*}})
+    // m68k: declare void @force_align_8({{.*}}byval([24 x i8]) align 8{{.*}})
 
-    // wasm: declare void @force_align_8({{.*}}byval(%ForceAlign8) align 8{{.*}})
+    // wasm: declare void @force_align_8({{.*}}byval([24 x i8]) align 8{{.*}})
 
-    // x86_64-linux: declare void @force_align_8({{.*}}byval(%ForceAlign8) align 8{{.*}})
+    // x86_64-linux: declare void @force_align_8({{.*}}byval([24 x i8]) align 8{{.*}})
 
     // x86_64-windows: declare void @force_align_8(
     // x86_64-windows-NOT: byval
     // x86_64-windows-SAME: align 8{{.*}})
 
-    // i686-linux: declare void @force_align_8({{.*}}byval(%ForceAlign8) align 4{{.*}})
+    // i686-linux: declare void @force_align_8({{.*}}byval([24 x i8]) align 4{{.*}})
 
     // i686-windows: declare void @force_align_8(
     // i686-windows-NOT: byval
     // i686-windows-SAME: align 8{{.*}})
     fn force_align_8(x: ForceAlign8);
 
-    // m68k: declare void @lower_fa8({{.*}}byval(%LowerFA8) align 4{{.*}})
+    // m68k: declare void @lower_fa8({{.*}}byval([24 x i8]) align 4{{.*}})
 
-    // wasm: declare void @lower_fa8({{.*}}byval(%LowerFA8) align 8{{.*}})
+    // wasm: declare void @lower_fa8({{.*}}byval([24 x i8]) align 8{{.*}})
 
-    // x86_64-linux: declare void @lower_fa8({{.*}}byval(%LowerFA8) align 8{{.*}})
+    // x86_64-linux: declare void @lower_fa8({{.*}}byval([24 x i8]) align 8{{.*}})
 
     // x86_64-windows: declare void @lower_fa8(
     // x86_64-windows-NOT: byval
     // x86_64-windows-SAME: align 8{{.*}})
 
-    // i686-linux: declare void @lower_fa8({{.*}}byval(%LowerFA8) align 4{{.*}})
+    // i686-linux: declare void @lower_fa8({{.*}}byval([24 x i8]) align 4{{.*}})
 
-    // i686-windows: declare void @lower_fa8({{.*}}byval(%LowerFA8) align 4{{.*}})
+    // i686-windows: declare void @lower_fa8({{.*}}byval([24 x i8]) align 4{{.*}})
     fn lower_fa8(x: LowerFA8);
 
-    // m68k: declare void @wrapped_fa8({{.*}}byval(%WrappedFA8) align 8{{.*}})
+    // m68k: declare void @wrapped_fa8({{.*}}byval([24 x i8]) align 8{{.*}})
 
-    // wasm: declare void @wrapped_fa8({{.*}}byval(%WrappedFA8) align 8{{.*}})
+    // wasm: declare void @wrapped_fa8({{.*}}byval([24 x i8]) align 8{{.*}})
 
-    // x86_64-linux: declare void @wrapped_fa8({{.*}}byval(%WrappedFA8) align 8{{.*}})
+    // x86_64-linux: declare void @wrapped_fa8({{.*}}byval([24 x i8]) align 8{{.*}})
 
     // x86_64-windows: declare void @wrapped_fa8(
     // x86_64-windows-NOT: byval
     // x86_64-windows-SAME: align 8{{.*}})
 
-    // i686-linux: declare void @wrapped_fa8({{.*}}byval(%WrappedFA8) align 4{{.*}})
+    // i686-linux: declare void @wrapped_fa8({{.*}}byval([24 x i8]) align 4{{.*}})
 
     // i686-windows: declare void @wrapped_fa8(
     // i686-windows-NOT: byval
     // i686-windows-SAME: align 8{{.*}})
     fn wrapped_fa8(x: WrappedFA8);
 
-    // m68k: declare void @transparent_fa8({{.*}}byval(%TransparentFA8) align 8{{.*}})
+    // m68k: declare void @transparent_fa8({{.*}}byval([24 x i8]) align 8{{.*}})
 
-    // wasm: declare void @transparent_fa8({{.*}}byval(%TransparentFA8) align 8{{.*}})
+    // wasm: declare void @transparent_fa8({{.*}}byval([24 x i8]) align 8{{.*}})
 
-    // x86_64-linux: declare void @transparent_fa8({{.*}}byval(%TransparentFA8) align 8{{.*}})
+    // x86_64-linux: declare void @transparent_fa8({{.*}}byval([24 x i8]) align 8{{.*}})
 
     // x86_64-windows: declare void @transparent_fa8(
     // x86_64-windows-NOT: byval
     // x86_64-windows-SAME: align 8{{.*}})
 
-    // i686-linux: declare void @transparent_fa8({{.*}}byval(%TransparentFA8) align 4{{.*}})
+    // i686-linux: declare void @transparent_fa8({{.*}}byval([24 x i8]) align 4{{.*}})
 
     // i686-windows: declare void @transparent_fa8(
     // i686-windows-NOT: byval
     // i686-windows-SAME: align 8{{.*}})
     fn transparent_fa8(x: TransparentFA8);
 
-    // m68k: declare void @force_align_16({{.*}}byval(%ForceAlign16) align 16{{.*}})
+    // m68k: declare void @force_align_16({{.*}}byval([80 x i8]) align 16{{.*}})
 
-    // wasm: declare void @force_align_16({{.*}}byval(%ForceAlign16) align 16{{.*}})
+    // wasm: declare void @force_align_16({{.*}}byval([80 x i8]) align 16{{.*}})
 
-    // x86_64-linux: declare void @force_align_16({{.*}}byval(%ForceAlign16) align 16{{.*}})
+    // x86_64-linux: declare void @force_align_16({{.*}}byval([80 x i8]) align 16{{.*}})
 
     // x86_64-windows: declare void @force_align_16(
     // x86_64-windows-NOT: byval
     // x86_64-windows-SAME: align 16{{.*}})
 
-    // i686-linux: declare void @force_align_16({{.*}}byval(%ForceAlign16) align 4{{.*}})
+    // i686-linux: declare void @force_align_16({{.*}}byval([80 x i8]) align 4{{.*}})
 
     // i686-windows: declare void @force_align_16(
     // i686-windows-NOT: byval

diff --git a/tests/codegen/align-enum.rs b/tests/codegen/align-enum.rs
@@ -8,7 +8,6 @@ pub enum Align64 {
     A(u32),
     B(u32),
 }
-// CHECK: %Align64 = type { i32, [15 x i32] }
 
 pub struct Nested64 {
     a: u8,

diff --git a/tests/codegen/align-struct.rs b/tests/codegen/align-struct.rs
@@ -5,27 +5,23 @@
 
 #[repr(align(64))]
 pub struct Align64(i32);
-// CHECK: %Align64 = type { i32, [15 x i32] }
 
 pub struct Nested64 {
     a: Align64,
     b: i32,
     c: i32,
     d: i8,
 }
-// CHECK: %Nested64 = type { %Align64, i32, i32, i8, [55 x i8] }
 
 pub enum Enum4 {
     A(i32),
     B(i32),
 }
-// No Aggregate type, and hence nothing in LLVM IR.
 
 pub enum Enum64 {
     A(Align64),
     B(i32),
 }
-// CHECK: %Enum64 = type { i32, [31 x i32] }
 
 // CHECK-LABEL: @align64
 #[no_mangle]

diff --git a/tests/codegen/function-arguments-noopt.rs b/tests/codegen/function-arguments-noopt.rs
@@ -42,7 +42,7 @@ pub fn borrow_call(x: &i32, f: fn(&i32) -> &i32) -> &i32 {
   f(x)
 }
 
-// CHECK: void @struct_(ptr sret(%S) align 4{{( %_0)?}}, ptr align 4 %x)
+// CHECK: void @struct_(ptr sret([32 x i8]) align 4{{( %_0)?}}, ptr align 4 %x)
 #[no_mangle]
 pub fn struct_(x: S) -> S {
   x
@@ -51,7 +51,7 @@ pub fn struct_(x: S) -> S {
 // CHECK-LABEL: @struct_call
 #[no_mangle]
 pub fn struct_call(x: S, f: fn(S) -> S) -> S {
-  // CHECK: call void %f(ptr sret(%S) align 4{{( %_0)?}}, ptr align 4 %{{.+}})
+  // CHECK: call void %f(ptr sret([32 x i8]) align 4{{( %_0)?}}, ptr align 4 %{{.+}})
   f(x)
 }
 

diff --git a/tests/codegen/function-arguments.rs b/tests/codegen/function-arguments.rs
@@ -188,7 +188,7 @@ pub fn notunpin_box(x: Box<NotUnpin>) -> Box<NotUnpin> {
   x
 }
 
-// CHECK: @struct_return(ptr noalias nocapture noundef sret(%S) align 4 dereferenceable(32){{( %_0)?}})
+// CHECK: @struct_return(ptr noalias nocapture noundef sret([32 x i8]) align 4 dereferenceable(32){{( %_0)?}})
 #[no_mangle]
 pub fn struct_return() -> S {
   S {

diff --git a/tests/codegen/mem-replace-big-type.rs b/tests/codegen/mem-replace-big-type.rs
@@ -23,7 +23,7 @@ pub fn replace_big(dst: &mut Big, src: Big) -> Big {
 // CHECK-NOT: call void @llvm.memcpy
 
 // For a large type, we expect exactly three `memcpy`s
-// CHECK-LABEL: define internal void @{{.+}}mem{{.+}}replace{{.+}}sret(%Big)
+// CHECK-LABEL: define internal void @{{.+}}mem{{.+}}replace{{.+}}sret([56 x i8])
 // CHECK-NOT: call void @llvm.memcpy
 // CHECK: call void @llvm.memcpy.{{.+}}(ptr align 8 %result, ptr align 8 %dest, i{{.*}} 56, i1 false)
 // CHECK-NOT: call void @llvm.memcpy