The optimization a + (-0.0f) -> a was being misapplied to a + (+0.0f) in the vector case (because
we weren't differntiating floating-point zeroinitializers from other zero-initializers)
which was causing problems for code relying upon a + (+0.0f) to, eg, flush denormals to
0. Make the scalar and vector cases have the same behaviour.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177279 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/IR/Constants.cpp b/lib/IR/Constants.cpp
index 0c7effb..70f7e01 100644
--- a/lib/IR/Constants.cpp
+++ b/lib/IR/Constants.cpp
@@ -47,6 +47,19 @@
if (const ConstantFP *CFP = dyn_cast<ConstantFP>(this))
return CFP->isZero() && CFP->isNegative();
+ // Equivalent for a vector of -0.0's.
+ if (const ConstantDataVector *CV = dyn_cast<ConstantDataVector>(this))
+ if (ConstantFP *SplatCFP = dyn_cast_or_null<ConstantFP>(CV->getSplatValue()))
+ if (SplatCFP && SplatCFP->isZero() && SplatCFP->isNegative())
+ return true;
+
+ // However, vectors of zeroes which are floating point represent +0.0's.
+ if (const ConstantAggregateZero *CAZ = dyn_cast<ConstantAggregateZero>(this))
+ if (const VectorType *VT = dyn_cast<VectorType>(CAZ->getType()))
+ if (VT->getElementType()->isFloatingPointTy())
+ // As it's a CAZ, we know it's the zero bit-pattern (ie, +0.0) in each element.
+ return false;
+
// Otherwise, just use +0.0.
return isNullValue();
}