[PATCH] D113442: [InstCombine] Enable fold select into operand for FAdd, FMul, and FSub.

[Huihui Zhang via Phabricator via llvm-commits]

huihuiz added a comment.

Thanks Sanjay for the comments, I will update unit test as suggested.

I have some concern when I checked with alive2, for fadd https://alive2.llvm.org/ce/z/UjAMM_  alive2 complaints mis-matched outputs.
For integer add this folding seems correct https://alive2.llvm.org/ce/z/oE4UQJ

Let me know if such transformation would be illegal for floating point type as alive2 pointed out, or there is anything I missed before I go fixing the unit test ?



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Comment at: llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp:257
   case Instruction::Sub:   // Can only fold on the amount subtracted.
+  case Instruction::FSub:
   case Instruction::Shl:   // Can only fold on the shift amount.
----------------
spatel wrote:
> Why exclude fdiv?
I checked with alive2, looks like adding fdiv, sdiv and udiv will trigger undefined behavior
https://alive2.llvm.org/ce/z/KvFYev
 


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