[TargetLowering] zextOrTrunc for xor and or if top bits are known 0, just like AND

[AZero13]

No description provided.

[llvmbot]

@llvm/pr-subscribers-llvm-selectiondag

Author: AZero13 (AZero13)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/146079.diff

1 Files Affected:

• (modified) llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp (+25-2)

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp index 000f8cc6786a5..62faf3cb1d8c8 100644 --- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp @@ -4240,14 +4240,26 @@ SDValue TargetLowering::foldSetCCWithOr(EVT VT, SDValue N0, SDValue N1, SelectionDAG &DAG = DCI.DAG; EVT OpVT = N0.getValueType(); - if (!N0.hasOneUse() || !OpVT.isInteger() || + if (N0.getOpcode() != ISD::OR || !OpVT.isInteger() || (Cond != ISD::SETEQ && Cond != ISD::SETNE)) return SDValue(); + // (X | Y) != 0 --> zextOrTrunc(X | Y) + // iff everything but LSB is known zero: + if (Cond == ISD::SETNE && isNullConstant(N1) && + (getBooleanContents(OpVT) == TargetLowering::UndefinedBooleanContent || + getBooleanContents(OpVT) == TargetLowering::ZeroOrOneBooleanContent)) { + unsigned NumEltBits = OpVT.getScalarSizeInBits(); + APInt UpperBits = APInt::getHighBitsSet(NumEltBits, NumEltBits - 1); + if (DAG.MaskedValueIsZero(N0, UpperBits)) + return DAG.getBoolExtOrTrunc(N0, DL, VT, OpVT); + } + // (X | Y) == Y // (X | Y) != Y SDValue X; - if (sd_match(N0, m_Or(m_Value(X), m_Specific(N1))) && hasAndNotCompare(N1)) { + if (N0.hasOneUse() && sd_match(N0, m_Or(m_Value(X), m_Specific(N1))) && + hasAndNotCompare(N1)) { // If the target supports an 'and-not' or 'and-complement' logic operation, // try to use that to make a comparison operation more efficient. @@ -4447,6 +4459,17 @@ SDValue TargetLowering::foldSetCCWithBinOp(EVT VT, SDValue N0, SDValue N1, if (X == N1) return DAG.getSetCC(DL, VT, Y, DAG.getConstant(0, DL, OpVT), Cond); + // (X ^ Y) != 0 --> zextOrTrunc(X ^ Y) + // iff everything but LSB is known zero: + if (BOpcode == ISD::XOR && Cond == ISD::SETNE && isNullConstant(N1) && + (getBooleanContents(OpVT) == TargetLowering::UndefinedBooleanContent || + getBooleanContents(OpVT) == TargetLowering::ZeroOrOneBooleanContent)) { + unsigned NumEltBits = OpVT.getScalarSizeInBits(); + APInt UpperBits = APInt::getHighBitsSet(NumEltBits, NumEltBits - 1); + if (DAG.MaskedValueIsZero(N0, UpperBits)) + return DAG.getBoolExtOrTrunc(N0, DL, VT, OpVT); + } + if (Y != N1) return SDValue(); 

[arsenm]

Missing tests