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codegen: use new {re,de,}allocator annotations in llvm #99574

Merged
merged 1 commit into from
Jul 26, 2022
Merged

codegen: use new {re,de,}allocator annotations in llvm #99574

merged 1 commit into from
Jul 26, 2022

Commits on Jul 26, 2022

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

    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 rust-lang#90032. [This
comment](rust-lang#24194 (comment))
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.
    @durin42
    durin42 committed Jul 26, 2022
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