From 5493feed251b00413a1978fc13a4a00fb7ec4e9e Mon Sep 17 00:00:00 2001 From: David Tweed Date: Mon, 18 Mar 2013 11:54:44 +0000 Subject: [PATCH] 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. llvm-svn: 177279 --- llvm/lib/IR/Constants.cpp | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp index 0c7effb..70f7e01 100644 --- a/llvm/lib/IR/Constants.cpp +++ b/llvm/lib/IR/Constants.cpp @@ -47,6 +47,19 @@ bool Constant::isNegativeZeroValue() const { if (const ConstantFP *CFP = dyn_cast(this)) return CFP->isZero() && CFP->isNegative(); + // Equivalent for a vector of -0.0's. + if (const ConstantDataVector *CV = dyn_cast(this)) + if (ConstantFP *SplatCFP = dyn_cast_or_null(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(this)) + if (const VectorType *VT = dyn_cast(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(); } -- 2.7.4