[PATCH] Add HLE target feature

[Jeffrey Yasskin]

On Wed, Feb 20, 2013 at 5:08 PM, Chandler Carruth <chandlerc at google.com> wrote:
> 1) The base case: we must have a single spec for the LLVM IR model. This
> should be tailored to the needs of optimizers, general enough to represent
> the various builtins, and still support efficient lowering to both X86 and
> potentially PPC implementations.

Oh yeah, I'd forgotten this part. Michael, could you point us to your
patch against http://llvm.org/docs/Atomics.html documenting your new
IR attributes? I didn't look through every patches, but I didn't see
any documentation in a brief scan.

Note that "Start a Hardware Lock Elision transaction with the atomic
operation." won't be sufficient, even if these are just
semantically-ignorable hints. I suspect that there's some
actually-useful semantics here that would make these operations usable
by other architectures if they ever add such instructions. For
example, see the documentation of the !nontemporal metadata.

Thanks,
Jeffrey