shylie/llvm-project
1
0
Fork 0
Code Issues Pull Requests Actions 6 Packages Projects Releases Wiki Activity

[DAG] move fold (select C, 0, 1 -> xor C, 1) to a helper function; NFC

Browse Source 
We're missing at least 3 other similar folds based on what we have in InstCombine. 

llvm-svn: 283596
This commit is contained in:
Sanjay Patel 2016-10-07 20:47:51 +00:00
parent 6982bb8f25
commit ecaf343fe7
1 changed files with 31 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -334,6 +334,7 @@ namespace {
SDValue visitShiftByConstant(SDNode *N, ConstantSDNode *Amt);
SDValue foldSelectOfConstants(SDNode *N);
bool SimplifySelectOps(SDNode *SELECT, SDValue LHS, SDValue RHS);
SDValue SimplifyBinOpWithSameOpcodeHands(SDNode *N);
SDValue SimplifySelect(const SDLoc &DL, SDValue N0, SDValue N1, SDValue N2);
@ -5105,24 +5106,14 @@ static SDValue combineMinNumMaxNum(const SDLoc &DL, EVT VT, SDValue LHS,
}
}
SDValue DAGCombiner::visitSELECT(SDNode *N) {
// TODO: We should handle other cases of selecting between {-1,0,1} here.
SDValue DAGCombiner::foldSelectOfConstants(SDNode *N) {
SDValue N0 = N->getOperand(0);
SDValue N1 = N->getOperand(1);
SDValue N2 = N->getOperand(2);
EVT VT = N->getValueType(0);
EVT VT0 = N0.getValueType();
// fold (select C, X, X) -> X
if (N1 == N2)
return N1;
if (const ConstantSDNode *N0C = dyn_cast<const ConstantSDNode>(N0)) {
// fold (select true, X, Y) -> X
// fold (select false, X, Y) -> Y
return !N0C->isNullValue() ? N1 : N2;
}
// fold (select C, 1, X) -> (or C, X)
if (VT == MVT::i1 && isOneConstant(N1))
return DAG.getNode(ISD::OR, SDLoc(N), VT, N0, N2);
// fold (select C, 0, 1) -> (xor C, 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
@ -5142,17 +5133,41 @@ SDValue DAGCombiner::visitSELECT(SDNode *N) {
SDValue XORNode;
if (VT == VT0) {
SDLoc DL(N);
return DAG.getNode(ISD::XOR, DL, VT0,
N0, DAG.getConstant(1, DL, VT0));
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));
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);
}
return SDValue();
}
SDValue DAGCombiner::visitSELECT(SDNode *N) {
SDValue N0 = N->getOperand(0);
SDValue N1 = N->getOperand(1);
SDValue N2 = N->getOperand(2);
EVT VT = N->getValueType(0);
EVT VT0 = N0.getValueType();
// fold (select C, X, X) -> X
if (N1 == N2)
return N1;
if (const ConstantSDNode *N0C = dyn_cast<const ConstantSDNode>(N0)) {
// fold (select true, X, Y) -> X
// fold (select false, X, Y) -> Y
return !N0C->isNullValue() ? N1 : N2;
}
// fold (select C, 1, X) -> (or C, X)
if (VT == MVT::i1 && isOneConstant(N1))
return DAG.getNode(ISD::OR, SDLoc(N), VT, N0, N2);
if (SDValue V = foldSelectOfConstants(N))
return V;
// fold (select C, 0, X) -> (and (not C), X)
if (VT == VT0 && VT == MVT::i1 && isNullConstant(N1)) {
SDValue NOTNode = DAG.getNOT(SDLoc(N0), N0, VT);