[PATCH] D146117: [RISCV]Optimize (riscvisd::select_cc x, 0, ne, x, 1)

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


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Comment at: llvm/lib/Target/RISCV/RISCVISelLowering.cpp:10914
       }
+      // (riscvisd::select_cc x, 0, ne, x, 1) -> (add x, (setcc x, 0, eq))
+      if (isNullConstant(RHS) && isOneConstant(FalseV) && LHS == TrueV &&
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We need to handle the commuted case `iscvisd::select_cc x, 0, eq, 1, x` as well.


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Comment at: llvm/lib/Target/RISCV/RISCVISelLowering.cpp:10917
+          CCVal == ISD::CondCode::SETNE) {
+        SDValue C = DAG.getSetCC(DL, VT, LHS, RHS, ISD::CondCode::SETEQ);
+        return DAG.getNode(ISD::ADD, DL, VT, LHS, C);
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I think you need to do
`LHS = DAG.getFreeze(LHS);`

to make this safe for undefined values.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D146117/new/

https://reviews.llvm.org/D146117