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[X86] combinePTESTCC - canonicalize constants to the RHS if the PTEST/TESTP node just uses the ZF flag #165601

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Merged
merged 1 commit into from
Oct 29, 2025
Merged

[X86] combinePTESTCC - canonicalize constants to the RHS if the PTEST/TESTP node just uses the ZF flag #165601

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9 changes: 5 additions & 4 deletions llvm/lib/Target/X86/X86ISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -48787,6 +48787,11 @@ static SDValue combinePTESTCC(SDValue EFLAGS, X86::CondCode &CC,
}

if (CC == X86::COND_E || CC == X86::COND_NE) {
// Canonicalize constant to RHS if we're just using ZF.
if (Op0 != Op1 && DAG.isConstantIntBuildVectorOrConstantInt(Op0) &&
!DAG.isConstantIntBuildVectorOrConstantInt(Op1))
return DAG.getNode(EFLAGS.getOpcode(), SDLoc(EFLAGS), VT, Op1, Op0);

// TESTZ(X,~Y) == TESTC(Y,X)
if (SDValue NotOp1 = IsNOT(Op1, DAG)) {
CC = (CC == X86::COND_E ? X86::COND_B : X86::COND_AE);
Expand Down Expand Up @@ -48850,10 +48855,6 @@ static SDValue combinePTESTCC(SDValue EFLAGS, X86::CondCode &CC,
}
}

// TESTZ(-1,X) == TESTZ(X,X)
if (ISD::isBuildVectorAllOnes(Op0.getNode()))
return DAG.getNode(EFLAGS.getOpcode(), SDLoc(EFLAGS), VT, Op1, Op1);

// TESTZ(X,-1) == TESTZ(X,X)
if (ISD::isBuildVectorAllOnes(Op1.getNode()))
return DAG.getNode(EFLAGS.getOpcode(), SDLoc(EFLAGS), VT, Op0, Op0);
Expand Down
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