Auto merge of #122050 - erikdesjardins:sret, r=nikic

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 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`

1 files changed, 31 insertions, 19 deletions

diff --git a/tests/codegen/repr/transparent-struct-ptr.rs b/tests/codegen/repr/transparent-struct-ptr.rs
index ff531029e04..26f0120752f 100644
--- a/tests/codegen/repr/transparent-struct-ptr.rs
+++ b/tests/codegen/repr/transparent-struct-ptr.rs
@@ -1,23 +1,36 @@
-//@ revisions: x32 x64 sparc sparc64
+//@ revisions: i686-linux i686-freebsd x64-linux x64-apple wasm32
 //@ compile-flags: -O -C no-prepopulate-passes
-//
-//@[x32] only-x86
-//@[x64] only-x86_64
-//@[sparc] only-sparc
-//@[sparc64] only-sparc64
-//@ ignore-windows
+
+//@[i686-linux] compile-flags: --target i686-unknown-linux-gnu
+//@[i686-linux] needs-llvm-components: x86
+//@[i686-freebsd] compile-flags: --target i686-unknown-freebsd
+//@[i686-freebsd] needs-llvm-components: x86
+//@[x64-linux] compile-flags: --target x86_64-unknown-linux-gnu
+//@[x64-linux] needs-llvm-components: x86
+//@[x64-apple] compile-flags: --target x86_64-apple-darwin
+//@[x64-apple] needs-llvm-components: x86
+//@[wasm32] compile-flags: --target wasm32-wasi
+//@[wasm32] needs-llvm-components: webassembly
+
 // See ./transparent.rs
 // Some platforms pass large aggregates using immediate arrays in LLVMIR
 // Other platforms pass large aggregates using struct pointer in LLVMIR
 // This covers the "struct pointer" case.
 
+#![feature(no_core, lang_items, transparent_unions)]
+#![crate_type = "lib"]
+#![no_std]
+#![no_core]
 
-#![feature(transparent_unions)]
+#[lang="sized"] trait Sized { }
+#[lang="freeze"] trait Freeze { }
+#[lang="copy"] trait Copy { }
 
-#![crate_type="lib"]
+impl Copy for [u32; 16] {}
+impl Copy for BigS {}
+impl Copy for BigU {}
 
 
-#[derive(Clone, Copy)]
 #[repr(C)]
 pub struct BigS([u32; 16]);
 
@@ -34,24 +47,23 @@ pub enum TeBigS {
     Variant(BigS),
 }
 
-// CHECK: define{{.*}}void @test_BigS(ptr [[BIGS_RET_ATTRS1:.*]] sret(%BigS) [[BIGS_RET_ATTRS2:.*]], ptr [[BIGS_ARG_ATTRS1:.*]] byval(%BigS) [[BIGS_ARG_ATTRS2:.*]])
+// CHECK: define{{.*}}void @test_BigS(ptr [[BIGS_RET_ATTRS1:.*]] sret([64 x i8]) [[BIGS_RET_ATTRS2:.*]], ptr [[BIGS_ARG_ATTRS1:.*]] byval([64 x i8]) [[BIGS_ARG_ATTRS2:.*]])
 #[no_mangle]
 pub extern "C" fn test_BigS(_: BigS) -> BigS { loop {} }
 
-// CHECK: define{{.*}}void @test_TsBigS(ptr [[BIGS_RET_ATTRS1]] sret(%TsBigS) [[BIGS_RET_ATTRS2]], ptr [[BIGS_ARG_ATTRS1]] byval(%TsBigS) [[BIGS_ARG_ATTRS2:.*]])
+// CHECK: define{{.*}}void @test_TsBigS(ptr [[BIGS_RET_ATTRS1]] sret([64 x i8]) [[BIGS_RET_ATTRS2]], ptr [[BIGS_ARG_ATTRS1]] byval([64 x i8]) [[BIGS_ARG_ATTRS2:.*]])
 #[no_mangle]
 pub extern "C" fn test_TsBigS(_: TsBigS) -> TsBigS { loop {} }
 
-// CHECK: define{{.*}}void @test_TuBigS(ptr [[BIGS_RET_ATTRS1]] sret(%TuBigS) [[BIGS_RET_ATTRS2]], ptr [[BIGS_ARG_ATTRS1]] byval(%TuBigS) [[BIGS_ARG_ATTRS2:.*]])
+// CHECK: define{{.*}}void @test_TuBigS(ptr [[BIGS_RET_ATTRS1]] sret([64 x i8]) [[BIGS_RET_ATTRS2]], ptr [[BIGS_ARG_ATTRS1]] byval([64 x i8]) [[BIGS_ARG_ATTRS2:.*]])
 #[no_mangle]
 pub extern "C" fn test_TuBigS(_: TuBigS) -> TuBigS { loop {} }
 
-// CHECK: define{{.*}}void @test_TeBigS(ptr [[BIGS_RET_ATTRS1]] sret(%"TeBigS::Variant") [[BIGS_RET_ATTRS2]], ptr [[BIGS_ARG_ATTRS1]] byval(%"TeBigS::Variant") [[BIGS_ARG_ATTRS2]])
+// CHECK: define{{.*}}void @test_TeBigS(ptr [[BIGS_RET_ATTRS1]] sret([64 x i8]) [[BIGS_RET_ATTRS2]], ptr [[BIGS_ARG_ATTRS1]] byval([64 x i8]) [[BIGS_ARG_ATTRS2]])
 #[no_mangle]
 pub extern "C" fn test_TeBigS(_: TeBigS) -> TeBigS { loop {} }
 
 
-#[derive(Clone, Copy)]
 #[repr(C)]
 pub union BigU {
     foo: [u32; 16],
@@ -70,18 +82,18 @@ pub enum TeBigU {
     Variant(BigU),
 }
 
-// CHECK: define{{.*}}void @test_BigU(ptr [[BIGU_RET_ATTRS1:.*]] sret(%BigU) [[BIGU_RET_ATTRS2:.*]], ptr [[BIGU_ARG_ATTRS1:.*]] byval(%BigU) [[BIGU_ARG_ATTRS2:.*]])
+// CHECK: define{{.*}}void @test_BigU(ptr [[BIGU_RET_ATTRS1:.*]] sret([64 x i8]) [[BIGU_RET_ATTRS2:.*]], ptr [[BIGU_ARG_ATTRS1:.*]] byval([64 x i8]) [[BIGU_ARG_ATTRS2:.*]])
 #[no_mangle]
 pub extern "C" fn test_BigU(_: BigU) -> BigU { loop {} }
 
-// CHECK: define{{.*}}void @test_TsBigU(ptr [[BIGU_RET_ATTRS1:.*]] sret(%TsBigU) [[BIGU_RET_ATTRS2:.*]], ptr [[BIGU_ARG_ATTRS1]] byval(%TsBigU) [[BIGU_ARG_ATTRS2]])
+// CHECK: define{{.*}}void @test_TsBigU(ptr [[BIGU_RET_ATTRS1:.*]] sret([64 x i8]) [[BIGU_RET_ATTRS2:.*]], ptr [[BIGU_ARG_ATTRS1]] byval([64 x i8]) [[BIGU_ARG_ATTRS2]])
 #[no_mangle]
 pub extern "C" fn test_TsBigU(_: TsBigU) -> TsBigU { loop {} }
 
-// CHECK: define{{.*}}void @test_TuBigU(ptr [[BIGU_RET_ATTRS1]] sret(%TuBigU) [[BIGU_RET_ATTRS2:.*]], ptr [[BIGU_ARG_ATTRS1]] byval(%TuBigU) [[BIGU_ARG_ATTRS2]])
+// CHECK: define{{.*}}void @test_TuBigU(ptr [[BIGU_RET_ATTRS1]] sret([64 x i8]) [[BIGU_RET_ATTRS2:.*]], ptr [[BIGU_ARG_ATTRS1]] byval([64 x i8]) [[BIGU_ARG_ATTRS2]])
 #[no_mangle]
 pub extern "C" fn test_TuBigU(_: TuBigU) -> TuBigU { loop {} }
 
-// CHECK: define{{.*}}void @test_TeBigU(ptr [[BIGU_RET_ATTRS1]] sret(%"TeBigU::Variant") [[BIGU_RET_ATTRS2:.*]], ptr [[BIGU_ARG_ATTRS1]] byval(%"TeBigU::Variant") [[BIGU_ARG_ATTRS2]])
+// CHECK: define{{.*}}void @test_TeBigU(ptr [[BIGU_RET_ATTRS1]] sret([64 x i8]) [[BIGU_RET_ATTRS2:.*]], ptr [[BIGU_ARG_ATTRS1]] byval([64 x i8]) [[BIGU_ARG_ATTRS2]])
 #[no_mangle]
 pub extern "C" fn test_TeBigU(_: TeBigU) -> TeBigU { loop {} }