[llvm-dev] [RFC] Adding support for marking allocator functions in LLVM IR

[Reid Kleckner via llvm-dev]

On Thu, Jan 6, 2022 at 1:41 AM Nikita Popov via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> An important bit I'm missing in this proposal is what the actual semantics
> of the "allocator" attribute are -- what optimizations is LLVM permitted to
> perform if this attribute is present?
> ...
> I assume the only optimization that "allocator" should control is the
> elimination of unused alloc+free pairs. Is that correct? Or are there other
> optimizations that should be bound to it?
>

Not to speak for Augie, but I think these predicates exist to support a
higher level goal of teaching LLVM to promote heap allocations to stack
allocations. LLVM can only currently do this when other passes (GVN+DSE)
promote all loads and stores to an allocation to registers, but you can
imagine building out more annotations to make other transforms possible.
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