From f8f4df59dc4afa5478d3e307e9d5aa38e3946755 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Mon, 11 Jan 2016 23:31:48 +0000
Subject: [PATCH] [LibCallSimplifier] use instruction-level fast-math-flags to
 transform log calls

Also, add tests to verify that we're checking 'fast' on both calls of each transform pair,
tighten the CHECK lines, and give the tests more meaningful names.

This is a continuation of:
http://reviews.llvm.org/rL255555
http://reviews.llvm.org/rL256871
http://reviews.llvm.org/rL256964
http://reviews.llvm.org/rL257400
http://reviews.llvm.org/rL257404



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257414 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Utils/SimplifyLibCalls.cpp |  6 ++-
 test/Transforms/InstCombine/log-pow.ll    | 64 +++++++++++++++--------
 2 files changed, 46 insertions(+), 24 deletions(-)

diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index ef700499ef2..24345465cf7 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1354,11 +1354,13 @@ Value *LibCallSimplifier::optimizeLog(CallInst *CI, IRBuilder<> &B) {
       !FT->getParamType(0)->isFloatingPointTy())
     return Ret;
 
-  if (!canUseUnsafeFPMath(CI->getParent()->getParent()))
+  if (!CI->hasUnsafeAlgebra())
     return Ret;
   Value *Op1 = CI->getArgOperand(0);
   auto *OpC = dyn_cast<CallInst>(Op1);
-  if (!OpC)
+
+  // The earlier call must also be unsafe in order to do these transforms.
+  if (!OpC || !OpC->hasUnsafeAlgebra())
     return Ret;
 
   // log(pow(x,y)) -> y*log(x)
diff --git a/test/Transforms/InstCombine/log-pow.ll b/test/Transforms/InstCombine/log-pow.ll
index c5ca1688d34..a0c10d0a0b8 100644
--- a/test/Transforms/InstCombine/log-pow.ll
+++ b/test/Transforms/InstCombine/log-pow.ll
@@ -1,41 +1,61 @@
 ; RUN: opt < %s -instcombine -S | FileCheck %s
 
-define double @mylog(double %x, double %y) #0 {
-entry:
+define double @log_pow(double %x, double %y) {
+  %pow = call fast double @llvm.pow.f64(double %x, double %y)
+  %call = call fast double @log(double %pow)
+  ret double %call
+}
+
+; CHECK-LABEL: define double @log_pow(
+; CHECK-NEXT:  %log = call fast double @log(double %x)
+; CHECK-NEXT:  %mul = fmul fast double %log, %y
+; CHECK-NEXT:  ret double %mul
+
+define double @log_pow_not_fast(double %x, double %y) {
   %pow = call double @llvm.pow.f64(double %x, double %y)
-  %call = call double @log(double %pow) #0
+  %call = call fast double @log(double %pow)
   ret double %call
 }
 
-; CHECK-LABEL: define double @mylog(
-; CHECK:   %log = call fast double @log(double %x) #0
-; CHECK:   %mul = fmul fast double %log, %y
-; CHECK:   ret double %mul
-; CHECK: }
+; CHECK-LABEL: define double @log_pow_not_fast(
+; CHECK-NEXT:  %pow = call double @llvm.pow.f64(double %x, double %y)
+; CHECK-NEXT:  %call = call fast double @log(double %pow)
+; CHECK-NEXT:  ret double %call
 
-define double @test2(double ()* %fptr, double %p1) #0 {
+define double @function_pointer(double ()* %fptr, double %p1) {
   %call1 = call double %fptr()
   %pow = call double @log(double %call1)
   ret double %pow
 }
 
-; CHECK-LABEL: @test2
-; CHECK: log
+; CHECK-LABEL: @function_pointer
+; CHECK-NEXT:  %call1 = call double %fptr()
+; CHECK-NEXT:  %pow = call double @log(double %call1)
+; CHECK-NEXT:  ret double %pow
+
+define double @log_exp2(double %x) {
+  %call2 = call fast double @exp2(double %x)
+  %call3 = call fast double @log(double %call2)
+  ret double %call3
+}
+
+; CHECK-LABEL: @log_exp2
+; CHECK-NEXT:  %call2 = call fast double @exp2(double %x)
+; CHECK-NEXT:  %logmul = fmul fast double %x, 0x3FE62E42FEFA39EF
+; CHECK-NEXT:  ret double %logmul
 
-define double @test3(double %x) #0 {
-  %call2 = call double @exp2(double %x) #0
-  %call3 = call double @log(double %call2) #0
+define double @log_exp2_not_fast(double %x) {
+  %call2 = call double @exp2(double %x)
+  %call3 = call fast double @log(double %call2)
   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: }
+; CHECK-LABEL: @log_exp2_not_fast
+; CHECK-NEXT:  %call2 = call double @exp2(double %x)
+; CHECK-NEXT:  %call3 = call fast double @log(double %call2)
+; CHECK-NEXT:  ret double %call3
 
-declare double @log(double) #0
-declare double @exp2(double) #0
+declare double @log(double)
+declare double @exp2(double)
 declare double @llvm.pow.f64(double, double)
 
-attributes #0 = { "unsafe-fp-math"="true" }
-- 
2.34.1