[llvm] [InstCombine] Resolve TODO: nnan nsz X / -0.0 -> copysign(inf, X) (PR #79766)

[Matt Arsenault via llvm-commits]

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@@ -1598,9 +1598,11 @@ Instruction *InstCombinerImpl::foldFDivConstantDivisor(BinaryOperator &I) {
       return BinaryOperator::CreateFDivFMF(X, NegC, &I);
 
   // nnan X / +0.0 -> copysign(inf, X)
-  if (I.hasNoNaNs() && match(I.getOperand(1), m_Zero())) {
+  // nnan nsz X / -0.0 -> copysign(inf, X)
+  if (I.hasNoNaNs() &&
+      (match(I.getOperand(1), m_PosZeroFP()) ||
+       (I.hasNoSignedZeros() && match(I.getOperand(1), m_NegZeroFP())))) {
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arsenm wrote:

The NSZ case can be relaxed to m_AnyZeroFP 

https://github.com/llvm/llvm-project/pull/79766