[InstCombine] Missed optimization in math expression: simplify calls exp functions
Summary: This patch enables folding following expressions under -ffast-math flag: exp(X) * exp(Y) -> exp(X + Y), exp2(X) * exp2(Y) -> exp2(X + Y). Motivation: https://bugs.llvm.org/show_bug.cgi?id=35594
Reviewers: hfinkel, spatel, efriedma, lebedev.ri
Reviewed By: spatel, lebedev.ri
Subscribers: lebedev.ri, llvm-commits
Differential Revision: https://reviews.llvm.org/D41342
llvm-svn: 352730
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index ca67348..ae3f081 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -441,6 +441,26 @@
return replaceInstUsesWith(I, Sqrt);
}
+ // exp(X) * exp(Y) -> exp(X + Y)
+ // Match as long as at least one of exp has only one use.
+ if (match(Op0, m_Intrinsic<Intrinsic::exp>(m_Value(X))) &&
+ match(Op1, m_Intrinsic<Intrinsic::exp>(m_Value(Y))) &&
+ (Op0->hasOneUse() || Op1->hasOneUse())) {
+ Value *XY = Builder.CreateFAddFMF(X, Y, &I);
+ Value *Exp = Builder.CreateUnaryIntrinsic(Intrinsic::exp, XY, &I);
+ return replaceInstUsesWith(I, Exp);
+ }
+
+ // exp2(X) * exp2(Y) -> exp2(X + Y)
+ // Match as long as at least one of exp2 has only one use.
+ if (match(Op0, m_Intrinsic<Intrinsic::exp2>(m_Value(X))) &&
+ match(Op1, m_Intrinsic<Intrinsic::exp2>(m_Value(Y))) &&
+ (Op0->hasOneUse() || Op1->hasOneUse())) {
+ Value *XY = Builder.CreateFAddFMF(X, Y, &I);
+ Value *Exp2 = Builder.CreateUnaryIntrinsic(Intrinsic::exp2, XY, &I);
+ return replaceInstUsesWith(I, Exp2);
+ }
+
// (X*Y) * X => (X*X) * Y where Y != X
// The purpose is two-fold:
// 1) to form a power expression (of X).