forked from OSchip/llvm-project
[SDAG] Actually check for a non-constant splat and clarify comments
around the handling of UNDEF lanes in boolean vector content analysis. The code before my changes here also failed to check for non-constant splats in a buildvector. I have no idea how to trigger this, I just spotted by inspection when trying to understand the code. It seems extremely unlikely to be worth the trouble to teach the only caller of this code (DAG combining setcc patterns) how to cleverly handle undef lanes, so I've just commented more thoroughly that we're giving up there. llvm-svn: 212515
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@ -1160,8 +1160,10 @@ bool TargetLowering::isConstTrueVal(const SDNode *N) const {
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IsVec = true;
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bool HasUndefElements;
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CN = BV->getConstantSplatNode(HasUndefElements);
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if (HasUndefElements)
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return false; // Can't blindly collapse the undef values.
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// Only interested in constant splats, and we don't try to handle undef
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// elements in identifying boolean constants.
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if (!CN || HasUndefElements)
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return false;
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}
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switch (getBooleanContents(IsVec)) {
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@ -1190,8 +1192,10 @@ bool TargetLowering::isConstFalseVal(const SDNode *N) const {
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IsVec = true;
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bool HasUndefElements;
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CN = BV->getConstantSplatNode(HasUndefElements);
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if (HasUndefElements)
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return false; // Can't blindly collapse the undef values.
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// Only interested in constant splats, and we don't try to handle undef
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// elements in identifying boolean constants.
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if (!CN || HasUndefElements)
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return false;
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}
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if (getBooleanContents(IsVec) == UndefinedBooleanContent)
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