fix handling of function attributes + optimize out pointer parameters #9109
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I landed most of this separately... but not the interesting parts. I'm still looking into why the segfault happens on x86. |
The `noalias` attributes were being set only on function definitions, not on all declarations. This is harmless for `noalias`, but prevented some optimization opportunities and is *not* harmless for other attributes like `sret` with ABI implications. Closes #9104
This brings Rust in line with how `clang` handles return pointers.
Example:
pub fn bar() -> [uint, .. 8] {
let a = [0, .. 8];
a
}
Before:
; Function Attrs: nounwind uwtable
define void @_ZN3bar17ha4635c6f704bfa334v0.0E([8 x i64]* nocapture, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #1 {
"function top level":
%a = alloca [8 x i64], align 8
%2 = bitcast [8 x i64]* %a to i8*
call void @llvm.memset.p0i8.i64(i8* %2, i8 0, i64 64, i32 8, i1 false)
%3 = bitcast [8 x i64]* %0 to i8*
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %3, i8* %2, i64 64, i32 8, i1 false)
ret void
}
After:
; Function Attrs: nounwind uwtable
define void @_ZN3bar17ha4635c6f704bfa334v0.0E([8 x i64]* noalias nocapture sret, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #1 {
"function top level":
%2 = bitcast [8 x i64]* %0 to i8*
call void @llvm.memset.p0i8.i64(i8* %2, i8 0, i64 64, i32 8, i1 false)
ret void
}
Closes #9072
Closes #7298
Closes #9154
also removes the unused `FastInvoke` wrapper, as it's never actually going to be used (we can't *partially* switch to `fastcc`, and this is only used for Rust functions)
bors
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flip1995
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Aug 11, 2022
`explicit_auto_deref` changes fixes rust-lang#9123 fixes rust-lang#9109 fixes rust-lang#9143 fixes rust-lang#9101 This avoid suggesting code which hits a rustc bug. Basically `&{x}` won't use auto-deref if the target type is `Sized`. changelog: Don't suggest using auto deref for block expressions when the target type is `Sized` changelog: Include the borrow in the suggestion for `explicit_auto_deref` changelog: Don't lint `explicit_auto_deref` on `dyn Trait` return changelog: Don't lint `explicit_auto_deref` when other adjustments are required changelog: Lint `explicit_auto_deref` in implicit return positions for closures
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