[PATCH] D117459: [PowerPC] Change CTR clobber estimation for 128-bit floating types

[ChenZheng via Phabricator via llvm-commits]

shchenz added inline comments.


================
Comment at: llvm/lib/Target/PowerPC/PPCTargetTransformInfo.cpp:663
+               J->getOperand(0)->getType()->getScalarType()->isFP128Ty()) {
+      return true;
     } else if (isa<UIToFPInst>(J) || isa<SIToFPInst>(J) ||
----------------
I think we are trying to handle fpext/fptrunc for fp128 type? If so, can we just explicitly handle them like:
```

     } else if (isa<FPTruncInst>(J) && cast<FPTruncInst>(J)->getSrcTy()->getScalarType()->isFP128Ty()) {
       return true;
     } else  if (isa<FPExtInst>(J) && cast<FPExtInst>(J)->getDestTy()->getScalarType()->isFP128Ty()) {
       return true;
     } 
```

Your patch seems not only change instructions `FPTruncInst` and `FPExtInst`. As you may have noted, ctr clobber check here is very sensitive especially for fp128/ppc_fp128. We met several issues before.

And have you checked with ppc_fp128 for the above two instructions `FPTruncInst` and `FPExtInst`? Can we expand them on PowerPC without potential writing ctr?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D117459/new/

https://reviews.llvm.org/D117459