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| author | Patrick Walton <pcwalton@fb.com> | 2022-10-31 20:38:40 -0700 |
|---|---|---|
| committer | Erik Desjardins <erikdesjardins@users.noreply.github.com> | 2023-07-10 19:19:30 -0400 |
| commit | 0becc89d4a75d14571b02fb34ec1e3a45c9fb9dc (patch) | |
| tree | 993d76d3838c65c16c50e796de364bd2eb2ec06c /tests/codegen/function-arguments.rs | |
| parent | 8ca44ef9caa4049d584fbbce218c219cdca33a2f (diff) | |
| download | rust-0becc89d4a75d14571b02fb34ec1e3a45c9fb9dc.tar.gz rust-0becc89d4a75d14571b02fb34ec1e3a45c9fb9dc.zip | |
rustc_target: Add alignment to indirectly-passed by-value types, correcting the
alignment of `byval` on x86 in the process. Commit 88e4d2c2918428d55e34cd57c11279ea839c8822 from five years ago removed support for alignment on indirectly-passed arguments because of problems with the `i686-pc-windows-msvc` target. Unfortunately, the `memcpy` optimizations I recently added to LLVM 16 depend on this to forward `memcpy`s. This commit attempts to fix the problems with `byval` parameters on that target and now correctly adds the `align` attribute. The problem is summarized in [this comment] by @eddyb. Briefly, 32-bit x86 has special alignment rules for `byval` parameters: for the most part, their alignment is forced to 4. This is not well-documented anywhere but in the Clang source. I looked at the logic in Clang `TargetInfo.cpp` and tried to replicate it here. The relevant methods in that file are `X86_32ABIInfo::getIndirectResult()` and `X86_32ABIInfo::getTypeStackAlignInBytes()`. The `align` parameter attribute for `byval` parameters in LLVM must match the platform ABI, or miscompilations will occur. Note that this doesn't use the approach suggested by eddyb, because I felt it was overkill to store the alignment in `on_stack` when special handling is really only needed for 32-bit x86. As a side effect, this should fix #80127, because it will make the `align` parameter attribute for `byval` parameters match the platform ABI on LLVM x86-64. [this comment]: https://github.com/rust-lang/rust/pull/80822#issuecomment-829985417
Diffstat (limited to 'tests/codegen/function-arguments.rs')
| -rw-r--r-- | tests/codegen/function-arguments.rs | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/tests/codegen/function-arguments.rs b/tests/codegen/function-arguments.rs index ccf4a5de327..2f047f10311 100644 --- a/tests/codegen/function-arguments.rs +++ b/tests/codegen/function-arguments.rs @@ -142,7 +142,7 @@ pub fn mutable_notunpin_borrow(_: &mut NotUnpin) { pub fn notunpin_borrow(_: &NotUnpin) { } -// CHECK: @indirect_struct({{%S\*|ptr}} noalias nocapture noundef readonly dereferenceable(32) %_1) +// CHECK: @indirect_struct({{%S\*|ptr}} noalias nocapture noundef readonly align 4 dereferenceable(32) %_1) #[no_mangle] pub fn indirect_struct(_: S) { } @@ -188,7 +188,7 @@ pub fn notunpin_box(x: Box<NotUnpin>) -> Box<NotUnpin> { x } -// CHECK: @struct_return({{%S\*|ptr}} noalias nocapture noundef sret(%S) dereferenceable(32){{( %_0)?}}) +// CHECK: @struct_return({{%S\*|ptr}} noalias nocapture noundef sret(%S) align 4 dereferenceable(32){{( %_0)?}}) #[no_mangle] pub fn struct_return() -> S { S { |