From 24c91af18b7b2da200d91cf5ae6a27f3be47cdc0 Mon Sep 17 00:00:00 2001
From: Davide Italiano <davide@freebsd.org>
Date: Mon, 30 Nov 2015 19:36:35 +0000
Subject: [PATCH] [SimplifyLibCalls] Transform log(exp2(y)) to y*log(2) under
fast-math.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254317 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/Transforms/Utils/SimplifyLibCalls.cpp | 10 +++++++++-
test/Transforms/InstCombine/log-pow-nofastmath.ll | 13 +++++++++++++
test/Transforms/InstCombine/log-pow.ll | 13 +++++++++++++
3 files changed, 35 insertions(+), 1 deletion(-)
diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 47e587fab7b..83afb1a65ac 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1322,6 +1322,15 @@ Value *LibCallSimplifier::optimizeLog(CallInst *CI, IRBuilder<> &B) {
return B.CreateFMul(OpC->getArgOperand(1),
EmitUnaryFloatFnCall(OpC->getOperand(0), Callee->getName(), B,
Callee->getAttributes()), "mul");
+
+ // log(exp2(y)) -> y*log(2)
+ if (F && Name == "log" && TLI->getLibFunc(F->getName(), Func) &&
+ TLI->has(Func) && Func == LibFunc::exp2)
+ return B.CreateFMul(
+ OpC->getArgOperand(0),
+ EmitUnaryFloatFnCall(ConstantFP::get(CI->getType(), 2.0),
+ Callee->getName(), B, Callee->getAttributes()),
+ "logmul");
return Ret;
}
@@ -2301,7 +2310,6 @@ void LibCallSimplifier::replaceAllUsesWith(Instruction *I, Value *With) {
// log, logf, logl:
// * log(exp(x)) -> x
// * log(exp(y)) -> y*log(e)
-// * log(exp2(y)) -> y*log(2)
// * log(exp10(y)) -> y*log(10)
// * log(sqrt(x)) -> 0.5*log(x)
//
diff --git a/test/Transforms/InstCombine/log-pow-nofastmath.ll b/test/Transforms/InstCombine/log-pow-nofastmath.ll
index 0811e63cc74..6c37c5466ce 100644
--- a/test/Transforms/InstCombine/log-pow-nofastmath.ll
+++ b/test/Transforms/InstCombine/log-pow-nofastmath.ll
@@ -13,5 +13,18 @@ entry:
; CHECK: ret double %call
; CHECK: }
+define double @test3(double %x) #0 {
+ %call2 = call double @exp2(double %x) #0
+ %call3 = call double @log(double %call2) #0
+ ret double %call3
+}
+
+; CHECK-LABEL: @test3
+; CHECK: %call2 = call double @exp2(double %x)
+; CHECK: %call3 = call double @log(double %call2)
+; CHECK: ret double %call3
+; CHECK: }
+
declare double @log(double) #0
+declare double @exp2(double)
declare double @llvm.pow.f64(double, double)
diff --git a/test/Transforms/InstCombine/log-pow.ll b/test/Transforms/InstCombine/log-pow.ll
index c98a1a5bc62..1acd0354431 100644
--- a/test/Transforms/InstCombine/log-pow.ll
+++ b/test/Transforms/InstCombine/log-pow.ll
@@ -22,7 +22,20 @@ define double @test2(double ()* %fptr, double %p1) #0 {
; CHECK-LABEL: @test2
; CHECK: log
+define double @test3(double %x) #0 {
+ %call2 = call double @exp2(double %x) #0
+ %call3 = call double @log(double %call2) #0
+ ret double %call3
+}
+
+; CHECK-LABEL: @test3
+; CHECK: %call2 = call double @exp2(double %x) #0
+; CHECK: %logmul = fmul fast double %x, 0x3FE62E42FEFA39EF
+; CHECK: ret double %logmul
+; CHECK: }
+
declare double @log(double) #0
+declare double @exp2(double) #0
declare double @llvm.pow.f64(double, double)
attributes #0 = { "unsafe-fp-math"="true" }