[llvm] [InstCombine] optimize exp(exp(x)) / exp(x) with fast-math (PR #66177)

[Nikita Popov via llvm-commits]

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@@ -1748,6 +1748,18 @@ Instruction *InstCombinerImpl::visitFDiv(BinaryOperator &I) {
 
   if (Instruction *Mul = foldFDivPowDivisor(I, Builder))
     return Mul;
+  Value *ExpX;
+  // exp(exp(X)) / exp(X) -> exp(exp(X) - X)
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nikic wrote:

Not seeing any checks for FMF here? Please add negative tests that the transform is not performed without needed flags.

https://github.com/llvm/llvm-project/pull/66177