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[SDAG] refactor foldSetCCWithRotate; NFC 

There are more potential optimizations to make here,
so rearrange to make it easier to append those.
This commit is contained in:
Sanjay Patel 2022-03-02 15:03:35 -05:00
parent 68069f27d9
commit c33dbc2a2d
1 changed files with 10 additions and 4 deletions
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14
llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
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@ -3819,17 +3819,23 @@ static SDValue foldSetCCWithRotate(EVT VT, SDValue N0, SDValue N1,
if (Cond != ISD::SETEQ && Cond != ISD::SETNE)
return SDValue();
if (N0.getOpcode() != ISD::ROTL && N0.getOpcode() != ISD::ROTR)
return SDValue();
auto *C1 = isConstOrConstSplat(N1, /* AllowUndefs */ true);
if (!C1 || !(C1->isZero() || C1->isAllOnes()))
return SDValue();
auto getRotateSource = [](SDValue X) {
if (X.getOpcode() == ISD::ROTL || X.getOpcode() == ISD::ROTR)
return X.getOperand(0);
return SDValue();
};
// Peek through a rotated value compared against 0 or -1:
// (rot X, Y) == 0/-1 --> X == 0/-1
// (rot X, Y) != 0/-1 --> X != 0/-1
return DAG.getSetCC(dl, VT, N0.getOperand(0), N1, Cond);
if (SDValue R = getRotateSource(N0))
return DAG.getSetCC(dl, VT, R, N1, Cond);
return SDValue();
}
/// Try to simplify a setcc built with the specified operands and cc. If it is