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Teach DAG combiner to turn a BUILD_VECTOR of UNDEFs into an UNDEF of vector type.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148297 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Craig Topper 2012-01-17 09:09:48 +00:00
parent 8b5a6b63dd
commit d3b588965d
1 changed files with 8 additions and 4 deletions
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12
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -7142,11 +7142,13 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
// optimizations. We do not handle sign-extend because we can't fill the sign
// using shuffles.
EVT SourceType = MVT::Other;
bool allAnyExt = true;
for (unsigned i = 0; i < NumInScalars; ++i) {
bool AllAnyExt = true;
bool AllUndef = true;
for (unsigned i = 0; i != NumInScalars; ++i) {
SDValue In = N->getOperand(i);
// Ignore undef inputs.
if (In.getOpcode() == ISD::UNDEF) continue;
AllUndef = false;
bool AnyExt = In.getOpcode() == ISD::ANY_EXTEND;
bool ZeroExt = In.getOpcode() == ISD::ZERO_EXTEND;
@ -7171,9 +7173,11 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
}
// Check if all of the extends are ANY_EXTENDs.
allAnyExt &= AnyExt;
AllAnyExt &= AnyExt;
}
if (AllUndef)
return DAG.getUNDEF(VT);
// In order to have valid types, all of the inputs must be extended from the
// same source type and all of the inputs must be any or zero extend.
@ -7193,7 +7197,7 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
bool isLE = TLI.isLittleEndian();
unsigned ElemRatio = OutScalarTy.getSizeInBits()/SourceType.getSizeInBits();
assert(ElemRatio > 1 && "Invalid element size ratio");
SDValue Filler = allAnyExt ? DAG.getUNDEF(SourceType):
SDValue Filler = AllAnyExt ? DAG.getUNDEF(SourceType):
DAG.getConstant(0, SourceType);
unsigned NewBVElems = ElemRatio * N->getValueType(0).getVectorNumElements();