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Checking a build_vector for an all-ones value.

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Type legalization can zero-extend the elements of the build_vector node, so,
for example, we may have an <8 x i8> with i32 elements of value 255. That
should return 'true' for the vector being all ones.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153203 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jim Grosbach 2012-03-21 17:48:04 +00:00
parent 208a4ff2b5
commit 331ff3b1d1
1 changed files with 14 additions and 5 deletions
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19
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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@ -124,20 +124,29 @@ bool ISD::isBuildVectorAllOnes(const SDNode *N) {
if (i == e) return false;
// Do not accept build_vectors that aren't all constants or which have non-~0
// elements.
// elements. We have to be a bit careful here, as the type of the constant
// may not be the same as the type of the vector elements due to type
// legalization (the elements are promoted to a legal type for the target and
// a vector of a type may be legal when the base element type is not).
// We only want to check enough bits to cover the vector elements, because
// we care if the resultant vector is all ones, not whether the individual
// constants are.
SDValue NotZero = N->getOperand(i);
unsigned EltSize = N->getValueType(0).getVectorElementType().getSizeInBits();
if (isa<ConstantSDNode>(NotZero)) {
if (!cast<ConstantSDNode>(NotZero)->isAllOnesValue())
if (cast<ConstantSDNode>(NotZero)->getAPIntValue().countTrailingOnes() <
EltSize)
return false;
} else if (isa<ConstantFPSDNode>(NotZero)) {
if (!cast<ConstantFPSDNode>(NotZero)->getValueAPF().
bitcastToAPInt().isAllOnesValue())
if (cast<ConstantFPSDNode>(NotZero)->getValueAPF()
.bitcastToAPInt().countTrailingOnes() < EltSize)
return false;
} else
return false;
// Okay, we have at least one ~0 value, check to see if the rest match or are
// undefs.
// undefs. Even with the above element type twiddling, this should be OK, as
// the same type legalization should have applied to all the elements.
for (++i; i != e; ++i)
if (N->getOperand(i) != NotZero &&
N->getOperand(i).getOpcode() != ISD::UNDEF)