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codegen: use new {re,de,}allocator annotations in llvm

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This obviates the patch that teaches LLVM internals about
_rust_{re,de}alloc functions by putting annotations directly in the IR
for the optimizer.

The sole test change is required to anchor FileCheck to the body of the
`box_uninitialized` method, so it doesn't see the `allocalign` on
`__rust_alloc` and get mad about the string `alloca` showing up. Since I
was there anyway, I added some checks on the attributes to prove the
right attributes got set.

While we're here, we also emit allocator attributes on
__rust_alloc_zeroed. This should allow LLVM to perform more
optimizations for zeroed blocks, and probably fixes #90032. [This
comment](https://github.com/rust-lang/rust/issues/24194#issuecomment-308791157)
mentions "weird UB-like behaviour with bitvec iterators in
rustc_data_structures" so we may need to back this change out if things
go wrong.

The new test cases require LLVM 15, so we copy them into LLVM
14-supporting versions, which we can delete when we drop LLVM 14.
This commit is contained in:
Augie Fackler 2022-03-21 15:30:54 -04:00
parent 2fdbf075cf
commit 130a1df71e
14 changed files with 356 additions and 4 deletions
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6
compiler/rustc_typeck/src/collect.rs
View file

@ -2775,6 +2775,12 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: DefId) -> CodegenFnAttrs {
}
} else if attr.has_name(sym::rustc_allocator_nounwind) {
codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
} else if attr.has_name(sym::rustc_reallocator) {
codegen_fn_attrs.flags |= CodegenFnAttrFlags::REALLOCATOR;
} else if attr.has_name(sym::rustc_deallocator) {
codegen_fn_attrs.flags |= CodegenFnAttrFlags::DEALLOCATOR;
} else if attr.has_name(sym::rustc_allocator_zeroed) {
codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR_ZEROED;
} else if attr.has_name(sym::naked) {
codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
} else if attr.has_name(sym::no_mangle) {