use -0.0 when creating an fneg instruction

Backends recognize (-0.0 - X) as the canonical form for fneg
and produce better code. Eg, ppc64 with 0.0:

   lis r2, ha16(LCPI0_0)
   lfs f0, lo16(LCPI0_0)(r2)
   fsubs f1, f0, f1
   blr

vs. -0.0:

   fneg f1, f1
   blr

Differential Revision: http://reviews.llvm.org/D6723

llvm-svn: 224583

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 39b71f37f8b..c2d2eec3fc3 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -759,7 +759,7 @@ Value *FAddCombine::createFSub(Value *Opnd0, Value *Opnd1) {
 }
 
 Value *FAddCombine::createFNeg(Value *V) {
-  Value *Zero = cast<Value>(ConstantFP::get(V->getType(), 0.0));
+  Value *Zero = cast<Value>(ConstantFP::getZeroValueForNegation(V->getType()));
   Value *NewV = createFSub(Zero, V);
   if (Instruction *I = dyn_cast<Instruction>(NewV))
     createInstPostProc(I, true); // fneg's don't receive instruction numbers.