[InstCombine] Missed optimization in math expression: squashing sqrt functions
Summary: This patch enables folding under -ffast-math flag sqrt(a) * sqrt(b) -> sqrt(a*b)
Reviewers: hfinkel, spatel, davide
Reviewed By: spatel, davide
Subscribers: davide, llvm-commits
Differential Revision: https://reviews.llvm.org/D41322
llvm-svn: 321637
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 541dde6..3860483 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -728,6 +728,23 @@
}
}
+ // sqrt(a) * sqrt(b) -> sqrt(a * b)
+ if (AllowReassociate &&
+ Op0->hasOneUse() && Op1->hasOneUse()) {
+ Value *Opnd0 = nullptr;
+ Value *Opnd1 = nullptr;
+ if (match(Op0, m_Intrinsic<Intrinsic::sqrt>(m_Value(Opnd0))) &&
+ match(Op1, m_Intrinsic<Intrinsic::sqrt>(m_Value(Opnd1)))) {
+ BuilderTy::FastMathFlagGuard Guard(Builder);
+ Builder.setFastMathFlags(I.getFastMathFlags());
+ Value *FMulVal = Builder.CreateFMul(Opnd0, Opnd1);
+ Value *Sqrt = Intrinsic::getDeclaration(I.getModule(),
+ Intrinsic::sqrt, I.getType());
+ Value *SqrtCall = Builder.CreateCall(Sqrt, FMulVal);
+ return replaceInstUsesWith(I, SqrtCall);
+ }
+ }
+
// Handle symmetric situation in a 2-iteration loop
Value *Opnd0 = Op0;
Value *Opnd1 = Op1;