[PATCH] D130839: [DAG] FoldConstantArithmetic - add initial support for undef elements in bitcasted binop constant folding

[Xiang Zhang via Phabricator via llvm-commits]

xiangzhangllvm added inline comments.


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Comment at: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:5583
+          BV2->getConstantRawBits(IsLE, EltBits, RawBits2, UndefElts2)) {
+        // Handle constant folding with UNDEF. TODO: Handle more cases.
+        auto FoldValueWithUndef = [](unsigned Opcode, const APInt &C1,
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Maybe better to add a small case here, some like
"old nodes"  --> "new nodes"


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Comment at: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:5589
+          if (!(IsUndef1 || IsUndef2))
+            Fold = FoldValue(Opcode, C1, C2);
+          else if (Opcode == ISD::AND || Opcode == ISD::MUL)
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Do we need to make sure the C1 C2 has no other uses ?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D130839/new/

https://reviews.llvm.org/D130839