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Auto merge of #121298 - nikic:writable, r=cuviper

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Set writable and dead_on_unwind attributes for sret arguments

Set the `writable` and `dead_on_unwind` attributes for `sret` arguments. This allows call slot optimization to remove more memcpy's.

See https://llvm.org/docs/LangRef.html#parameter-attributes for the specification of these attributes. In short, the statement we're making here is that:

 * The return slot is writable.
 * The return slot will not be read if the function unwinds.

Fixes https://github.com/rust-lang/rust/issues/90595.
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bors 2024-04-25 04:31:56 +00:00
commit 284f94f9c0
7 changed files with 33 additions and 4 deletions
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2
tests/codegen/function-arguments.rs
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@ -197,7 +197,7 @@ pub fn notunpin_box(x: Box<NotUnpin>) -> Box<NotUnpin> {
x
}
// CHECK: @struct_return(ptr noalias nocapture noundef sret([32 x i8]) align 4 dereferenceable(32){{( %_0)?}})
// CHECK: @struct_return(ptr{{( dead_on_unwind)?}} noalias nocapture noundef{{( writable)?}} sret([32 x i8]) align 4 dereferenceable(32){{( %_0)?}})
#[no_mangle]
pub fn struct_return() -> S {
S {