[PATCH] D16239: Fix PR25526 by adding back limited cmpxchg pseudo-Insts
Tim Northover via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 3 11:47:57 PST 2016
On 15 January 2016 at 20:25, Ahmed Bougacha <ahmed.bougacha at gmail.com> wrote:
> So, I cringe as I'm typing this, but what about using an intrinsic for
> the comparison as well?
I've finally gotten around to attempting this idea properly, and I
don't think it's going to help. Through some hackery in FastISel, I
did manage to ensure the basic block's outs were physical, but ISel
specifically assumes that VRegs are assigned to anything escaping a
basic block (and asserts if not, in CopyValueToVirtualRegister).
That's not an assertion I'd be comfortable relaxing, even if the rest
of the patch was clean.
In general, I think that would also be too intrusive for the atomic
expansion pass and scarily fragile (we'd probably need a separate DAG
implementation as a fallback anyway in case the code isn't exactly
I'm updating the previous patch at the moment with your last round of
comments, but any other ideas are still welcome.
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