InstCombine: If the divisor of an fdiv has an exact inverse, turn it into an fmul.
Fixes PR9587.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128546 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index d1a1fd6..6651387 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -452,6 +452,18 @@
if (Value *V = SimplifyFDivInst(Op0, Op1, TD))
return ReplaceInstUsesWith(I, V);
+ if (ConstantFP *Op1C = dyn_cast<ConstantFP>(Op1)) {
+ const APFloat &Op1F = Op1C->getValueAPF();
+
+ // If the divisor has an exact multiplicative inverse we can turn the fdiv
+ // into a cheaper fmul.
+ APFloat Reciprocal(Op1F.getSemantics());
+ if (Op1F.getExactInverse(&Reciprocal)) {
+ ConstantFP *RFP = ConstantFP::get(Builder->getContext(), Reciprocal);
+ return BinaryOperator::CreateFMul(Op0, RFP);
+ }
+ }
+
return 0;
}