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[DAGCombine] visitMULHS/visitMULHU - isBuildVectorAllZeros doesn't mean node is all zeros 

Return a proper zero vector, just in case some elements are undef.

Noticed by inspection after dealing with a similar issue in PR43159.

llvm-svn: 370460
This commit is contained in:
Simon Pilgrim 2019-08-30 10:42:14 +00:00
parent 01a3c25c27
commit 7cbf823f93
1 changed files with 8 additions and 8 deletions
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16
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -4183,10 +4183,10 @@ SDValue DAGCombiner::visitMULHS(SDNode *N) {
if (VT.isVector()) {
// fold (mulhs x, 0) -> 0
if (ISD::isBuildVectorAllZeros(N1.getNode()))
return N1;
if (ISD::isBuildVectorAllZeros(N0.getNode()))
return N0;
// do not return N0/N1, because undef node may exist.
if (ISD::isBuildVectorAllZeros(N0.getNode()) ||
ISD::isBuildVectorAllZeros(N1.getNode()))
return DAG.getConstant(0, DL, VT);
}
// fold (mulhs x, 0) -> 0
@ -4230,10 +4230,10 @@ SDValue DAGCombiner::visitMULHU(SDNode *N) {
if (VT.isVector()) {
// fold (mulhu x, 0) -> 0
if (ISD::isBuildVectorAllZeros(N1.getNode()))
return N1;
if (ISD::isBuildVectorAllZeros(N0.getNode()))
return N0;
// do not return N0/N1, because undef node may exist.
if (ISD::isBuildVectorAllZeros(N0.getNode()) ||
ISD::isBuildVectorAllZeros(N1.getNode()))
return DAG.getConstant(0, DL, VT);
}
// fold (mulhu x, 0) -> 0