[InstSimplify] Missed optimization in math expression: log10(pow(10.0,x)) == x, log2(pow(2.0,x)) == x
Summary: This patch enables folding following instructions under -ffast-math flag: log10(pow(10.0,x)) -> x, log2(pow(2.0,x)) -> x
Reviewers: hfinkel, spatel, efriedma, craig.topper, zvi, majnemer, lebedev.ri
Reviewed By: spatel, lebedev.ri
Subscribers: lebedev.ri, llvm-commits
Differential Revision: https://reviews.llvm.org/D41940
llvm-svn: 352981
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index ed3ba77..c83d62f 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4940,7 +4940,15 @@
case Intrinsic::log2:
// log2(exp2(x)) -> x
if (Q.CxtI->hasAllowReassoc() &&
- match(Op0, m_Intrinsic<Intrinsic::exp2>(m_Value(X)))) return X;
+ (match(Op0, m_Intrinsic<Intrinsic::exp2>(m_Value(X))) ||
+ match(Op0, m_Intrinsic<Intrinsic::pow>(m_SpecificFP(2.0),
+ m_Value(X))))) return X;
+ break;
+ case Intrinsic::log10:
+ // log10(pow(10.0, x)) -> x
+ if (Q.CxtI->hasAllowReassoc() &&
+ match(Op0, m_Intrinsic<Intrinsic::pow>(m_SpecificFP(10.0),
+ m_Value(X)))) return X;
break;
default:
break;