llvm-project

cc1ca591 - [GlobalIsel] Add failure memory order to LegalityQuery (NFC) (#162284)

[GlobalIsel] Add failure memory order to LegalityQuery (NFC) (#162284) The `cmpxchg` instruction has two memory orders, one for success and one for failure. Prior to this patch `LegalityQuery` only exposed a single memory order, that of the success case. This meant that it was not generally possible to legalize `cmpxchg` instructions based on their memory orders. Add a `FailureOrdering` field to `LegalityQuery::MemDesc`; it is only set for `cmpxchg` instructions, otherwise it is `NotAtomic`. I didn't rename `Ordering` to `SuccessOrdering` or similar to avoid breaking changes for out of tree targets. The new field does not increase `sizeof(MemDesc)`, it falls into previous padding bits due to alignment, so I'd expect there to be no performance impact for this change. Verified no breakage via check-llvm in build with AMDGPU, AArch64, and X86 targets enabled.