[PATCH] D76585: [PowerPC] Require NSZ flag for c-a*b to FNMSUB

Thu Mar 26 07:01:04 PDT 2020

spatel added a subscriber: qshanz.
spatel added inline comments.

================
Comment at: llvm/test/CodeGen/PowerPC/fma-negate.ll:289
+; NO-VSX-NEXT:    fmadd 1, 1, 3, 5
+; NO-VSX-NEXT:    fmadd 2, 0, 4, 6
 ; NO-VSX-NEXT:    blr
----------------
qiucf wrote:
> spatel wrote:
> > qiucf wrote:
> > > This should be a regression. And the reason is `SplitVectorRes` did not pass `SDNode` flags to legalized ones. If that's truly a bug, I will cook a patch for it.
> > This should **not** be a regression, right? If we dropped the flags during legalization, that is a bug.
> I posted the fix at D76832 :)
Thanks! Please rebase this patch after that the other one is pushed.
PPC experts can judge whether we want to proceed with this one or wait for possible improvements in getNegatibleCost().
We have known bugs with that logic (D76638, D76439), but I'm not sure yet what the best solution is. @qshanz may have a better idea.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76585/new/

https://reviews.llvm.org/D76585