[llvm-dev] rL296252 Made large integer operation codegen significantly worse.

Amaury SECHET via llvm-dev llvm-dev at lists.llvm.org
Sat Feb 25 09:51:57 PST 2017


I'm working with workload where the bottleneck is cryptographic signature
checks. Or, in compiler terms, most large integer operations.

Looking at rL296252 , the state of affair in that area degraded quite
significantly, see test/CodeGen/X86/i256-add.ll for instance.

Is there some kind of work in progress here and it is expected to get
better ? Because if not, that's a big problem. It looks like the problem is
that the compiler now choose to use pushfq/popfq in some cases rather than
chaining adc to propagate the carry in additions.

I hope this can get sorted out quickly. I'm happy to help if that is


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