[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

diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 47e587fab7b6a94f585a36a26d47b909fde4a72d..83afb1a65ac09dbdd9ce45a2517338619a18c20f 100644 (file)
--- 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 0811e63cc74ac0f8b21cc38bea71ec430a9144e3..6c37c5466cea8044d766a9e5038f175b7e034c85 100644 (file)
--- 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 c98a1a5bc6282882b01e99c18a9b8e6de6942b18..1acd0354431e41b3391ce1c243fcf428d68b1e2f 100644 (file)
--- 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" }