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

[Qing Shan Zhang via Phabricator via llvm-commits]

steven.zhang added a comment.

LGTM now overall with some minor comments. As you are adding the pattern for VNMSUBFP, I would suggest you do it in another patch.



================
Comment at: llvm/lib/Target/PowerPC/PPCISelLowering.cpp:15818
+    const TargetOptions &Options = getTargetMachine().Options;
+    unsigned InvertedOpc = invertFMAOpcode(Opc);
+    SDValue N0 = Op.getOperand(0);
----------------

 Remove the InvertedOpc but use FMA directly as we know that it is FNMSUB now. And move the invertFMAOpcode as lambda of the getNegatedExpression.


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Comment at: llvm/lib/Target/PowerPC/PPCISelLowering.cpp:15833
+
+    // Transformations may change sign of zeroes.
+    if (Flags.hasNoSignedZeros() || Options.NoSignedZerosFPMath) {
----------------
It will be great if you can add more wording on how it changes the sign of zeroes here. 


Repository:
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  https://reviews.llvm.org/D76585/new/

https://reviews.llvm.org/D76585