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[DAG] clean up foldSelectOfConstants(); NFCI

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Rename variables, simplify logic. 
Not clear yet why we don't handle a target with ZeroOrNegativeOneBooleanContent too.

llvm-svn: 283613
This commit is contained in:
Sanjay Patel 2016-10-07 21:55:42 +00:00
parent 99e8d201a0
commit 1d88c15c1d
1 changed files with 14 additions and 19 deletions
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33
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -5108,13 +5108,14 @@ static SDValue combineMinNumMaxNum(const SDLoc &DL, EVT VT, SDValue LHS,
// TODO: We should handle other cases of selecting between {-1,0,1} here.
SDValue DAGCombiner::foldSelectOfConstants(SDNode *N) {
SDValue N0 = N->getOperand(0);
SDValue Cond = N->getOperand(0);
SDValue N1 = N->getOperand(1);
SDValue N2 = N->getOperand(2);
EVT VT = N->getValueType(0);
EVT VT0 = N0.getValueType();
EVT CondVT = Cond.getValueType();
SDLoc DL(N);
// fold (select C, 0, 1) -> (xor C, 1)
// fold (select Cond, 0, 1) -> (xor Cond, 1)
// We can't do this reliably if integer based booleans have different contents
// to floating point based booleans. This is because we can't tell whether we
// have an integer-based boolean or a floating-point-based boolean unless we
@ -5124,23 +5125,17 @@ SDValue DAGCombiner::foldSelectOfConstants(SDNode *N) {
// in another basic block or it could require searching a complicated
// expression.
if (VT.isInteger() &&
(VT0 == MVT::i1 || (VT0.isInteger() &&
TLI.getBooleanContents(false, false) ==
TLI.getBooleanContents(false, true) &&
TLI.getBooleanContents(false, false) ==
TargetLowering::ZeroOrOneBooleanContent)) &&
(CondVT == MVT::i1 || (CondVT.isInteger() &&
TLI.getBooleanContents(false, true) ==
TargetLowering::ZeroOrOneBooleanContent &&
TLI.getBooleanContents(false, false) ==
TargetLowering::ZeroOrOneBooleanContent)) &&
isNullConstant(N1) && isOneConstant(N2)) {
SDValue XORNode;
if (VT == VT0) {
SDLoc DL(N);
return DAG.getNode(ISD::XOR, DL, VT0, N0, DAG.getConstant(1, DL, VT0));
}
SDLoc DL0(N0);
XORNode = DAG.getNode(ISD::XOR, DL0, VT0, N0, DAG.getConstant(1, DL0, VT0));
AddToWorklist(XORNode.getNode());
if (VT.bitsGT(VT0))
return DAG.getNode(ISD::ZERO_EXTEND, SDLoc(N), VT, XORNode);
return DAG.getNode(ISD::TRUNCATE, SDLoc(N), VT, XORNode);
SDValue NotCond = DAG.getNode(ISD::XOR, DL, CondVT, Cond,
DAG.getConstant(1, DL, CondVT));
if (VT.bitsEq(CondVT))
return NotCond;
return DAG.getZExtOrTrunc(NotCond, DL, VT);
}
return SDValue();