[InstSimplify] (X * Y) / Y --> X for relaxed floating-point ops
This is the FP counterpart that was mentioned in PR35709:
https://bugs.llvm.org/show_bug.cgi?id=35709
Differential Revision: https://reviews.llvm.org/D42385
llvm-svn: 323716
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index a258c4d..b81ecc8 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4298,9 +4298,15 @@
if (FMF.noNaNs()) {
// X / X -> 1.0 is legal when NaNs are ignored.
+ // We can ignore infinities because INF/INF is NaN.
if (Op0 == Op1)
return ConstantFP::get(Op0->getType(), 1.0);
+ // (X * Y) / Y --> X if we can reassociate to the above form.
+ Value *X;
+ if (FMF.allowReassoc() && match(Op0, m_c_FMul(m_Value(X), m_Specific(Op1))))
+ return X;
+
// -X / X -> -1.0 and
// X / -X -> -1.0 are legal when NaNs are ignored.
// We can ignore signed zeros because +-0.0/+-0.0 is NaN and ignored.