[SimplifyLibCalls] propagate FMF when folding pow(x, 2.0) call (PR35601)

This should fix the larger problem with sqrt shown in:
https://bugs.llvm.org/show_bug.cgi?id=35601

llvm-svn: 320310

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index c392492e331f38d0f555fea26a0e6a7201710005..273a5e79a7d250d5909c389a9760aa9d3ad6a22d 100644 (file)
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1206,8 +1206,13 @@ Value *LibCallSimplifier::optimizePow(CallInst *CI, IRBuilder<> &B) {
 
   if (Op2C->isExactlyValue(1.0)) // pow(x, 1.0) -> x
     return Op1;
-  if (Op2C->isExactlyValue(2.0)) // pow(x, 2.0) -> x*x
+  if (Op2C->isExactlyValue(2.0)) {
+    // pow(x, 2.0) --> x * x
+    IRBuilder<>::FastMathFlagGuard Guard(B);
+    B.setFastMathFlags(CI->getFastMathFlags());
     return B.CreateFMul(Op1, Op1, "pow2");
+  }
+  // FIXME: This should propagate the FMF of the call to the fdiv.
   if (Op2C->isExactlyValue(-1.0)) // pow(x, -1.0) -> 1.0/x
     return B.CreateFDiv(ConstantFP::get(CI->getType(), 1.0), Op1, "powrecip");
 

diff --git a/llvm/test/Transforms/InstCombine/pow-1.ll b/llvm/test/Transforms/InstCombine/pow-1.ll
index 6c9f39fc0e014a604845776ebbcbf74e25131bfa..c7ca3cf7547346f7a4340ed2f00c617a128076bb 100644 (file)
--- a/llvm/test/Transforms/InstCombine/pow-1.ll
+++ b/llvm/test/Transforms/InstCombine/pow-1.ll
@@ -133,11 +133,11 @@ define float @pow2_strict(float %x) {
   ret float %r
 }
 
-; FIXME: Don't drop the FMF - PR35601 ( https://bugs.llvm.org/show_bug.cgi?id=35601 )
+; Don't drop the FMF - PR35601 ( https://bugs.llvm.org/show_bug.cgi?id=35601 )
 
 define float @pow2_fast(float %x) {
 ; CHECK-LABEL: @pow2_fast(
-; CHECK-NEXT:    [[POW2:%.*]] = fmul float %x, %x
+; CHECK-NEXT:    [[POW2:%.*]] = fmul fast float %x, %x
 ; CHECK-NEXT:    ret float [[POW2]]
 ;
   %r = call fast float @powf(float %x, float 2.0)