commit 1aeed6a9557a13ff76ecf314ad6ae8c270acced9
author Davide Italiano <davide@freebsd.org> Mon Nov 30 19:36:35 2015 +0000
committer Davide Italiano <davide@freebsd.org> Mon Nov 30 19:36:35 2015 +0000
tree e01197f49145c7ae5412a7e93241818e8bdbdfc2
parent 9586a388706f2ed7cfd29ce863dded4a628142fb

[SimplifyLibCalls] Transform log(exp2(y)) to y*log(2) under fast-math.

llvm-svn: 254317

llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 47e587f..83afb1a 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1322,6 +1322,15 @@
     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 @@
 // 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)
 //

llvm/test/Transforms/InstCombine/log-pow-nofastmath.ll

diff --git a/llvm/test/Transforms/InstCombine/log-pow-nofastmath.ll b/llvm/test/Transforms/InstCombine/log-pow-nofastmath.ll
index 0811e63..6c37c54 100644
--- a/llvm/test/Transforms/InstCombine/log-pow-nofastmath.ll
+++ b/llvm/test/Transforms/InstCombine/log-pow-nofastmath.ll
@@ -13,5 +13,18 @@
 ; 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)

llvm/test/Transforms/InstCombine/log-pow.ll

diff --git a/llvm/test/Transforms/InstCombine/log-pow.ll b/llvm/test/Transforms/InstCombine/log-pow.ll
index c98a1a5..1acd035 100644
--- a/llvm/test/Transforms/InstCombine/log-pow.ll
+++ b/llvm/test/Transforms/InstCombine/log-pow.ll
@@ -22,7 +22,20 @@
 ; 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" }