[PATCH] D124930: [DagCombine] Fold (X & ~Y) | Y with truncated not

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: llvm/include/llvm/CodeGen/SelectionDAGNodes.h:1691
 
+/// If \p V is a bitwise note, returns the inverted operand. Otherwise returns
+/// and empty SDValue. Only bits set in \p Mask are required to be inverted,
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note -> node


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Comment at: llvm/include/llvm/CodeGen/SelectionDAGNodes.h:1692
+/// If \p V is a bitwise note, returns the inverted operand. Otherwise returns
+/// and empty SDValue. Only bits set in \p Mask are required to be inverted,
+/// other bits may be arbitrary.
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an empty SDValue


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Comment at: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:4688
 // Only bits set in Mask must be negated, other bits may be arbitrary.
-static SDValue getBitwiseNotOperand(SDValue V, SDValue Mask) {
-  if (isBitwiseNot(V, true))
+SDValue llvm::getBitwiseNotOperand(SDValue V, SDValue Mask, bool AllowUndefs) {
+  if (isBitwiseNot(V, AllowUndefs))
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Would this be more generally useful if we replaced Mask with a APInt DemandedBits?


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  https://reviews.llvm.org/D124930/new/

https://reviews.llvm.org/D124930