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[DAGCombine] Merge visitSSUBO+visitUSUBO into visitSUBO. NFCI.

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llvm-svn: 355688
This commit is contained in:
Simon Pilgrim 2019-03-08 11:16:55 +00:00
parent 228c3405e1
commit 5d65b16758
1 changed files with 8 additions and 33 deletions
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41
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -299,8 +299,7 @@ namespace {
SDValue visitUADDO(SDNode *N);
SDValue visitUADDOLike(SDValue N0, SDValue N1, SDNode *N);
SDValue visitSUBC(SDNode *N);
SDValue visitSSUBO(SDNode *N);
SDValue visitUSUBO(SDNode *N);
SDValue visitSUBO(SDNode *N);
SDValue visitADDE(SDNode *N);
SDValue visitADDCARRY(SDNode *N);
SDValue visitADDCARRYLike(SDValue N0, SDValue N1, SDValue CarryIn, SDNode *N);
@ -1497,8 +1496,8 @@ SDValue DAGCombiner::visit(SDNode *N) {
case ISD::SADDO: return visitSADDO(N);
case ISD::UADDO: return visitUADDO(N);
case ISD::SUBC: return visitSUBC(N);
case ISD::SSUBO: return visitSSUBO(N);
case ISD::USUBO: return visitUSUBO(N);
case ISD::SSUBO:
case ISD::USUBO: return visitSUBO(N);
case ISD::ADDE: return visitADDE(N);
case ISD::ADDCARRY: return visitADDCARRY(N);
case ISD::SUBE: return visitSUBE(N);
@ -2925,35 +2924,11 @@ SDValue DAGCombiner::visitSUBC(SDNode *N) {
return SDValue();
}
// TODO: merge this with DAGCombiner::visitUSUBO
SDValue DAGCombiner::visitSSUBO(SDNode *N) {
SDValue N0 = N->getOperand(0);
SDValue N1 = N->getOperand(1);
EVT VT = N0.getValueType();
EVT CarryVT = N->getValueType(1);
SDLoc DL(N);
// If the flag result is dead, turn this into an SUB.
if (!N->hasAnyUseOfValue(1))
return CombineTo(N, DAG.getNode(ISD::SUB, DL, VT, N0, N1),
DAG.getUNDEF(CarryVT));
// fold (ssubo x, x) -> 0 + no borrow
if (N0 == N1)
return CombineTo(N, DAG.getConstant(0, DL, VT),
DAG.getConstant(0, DL, CarryVT));
// fold (ssubo x, 0) -> x + no borrow
if (isNullOrNullSplat(N1))
return CombineTo(N, N0, DAG.getConstant(0, DL, CarryVT));
return SDValue();
}
SDValue DAGCombiner::visitUSUBO(SDNode *N) {
SDValue DAGCombiner::visitSUBO(SDNode *N) {
SDValue N0 = N->getOperand(0);
SDValue N1 = N->getOperand(1);
EVT VT = N0.getValueType();
bool IsSigned = (ISD::SSUBO == N->getOpcode());
EVT CarryVT = N->getValueType(1);
SDLoc DL(N);
@ -2963,17 +2938,17 @@ SDValue DAGCombiner::visitUSUBO(SDNode *N) {
return CombineTo(N, DAG.getNode(ISD::SUB, DL, VT, N0, N1),
DAG.getUNDEF(CarryVT));
// fold (usubo x, x) -> 0 + no borrow
// fold (subo x, x) -> 0 + no borrow
if (N0 == N1)
return CombineTo(N, DAG.getConstant(0, DL, VT),
DAG.getConstant(0, DL, CarryVT));
// fold (usubo x, 0) -> x + no borrow
// fold (subo x, 0) -> x + no borrow
if (isNullOrNullSplat(N1))
return CombineTo(N, N0, DAG.getConstant(0, DL, CarryVT));
// Canonicalize (usubo -1, x) -> ~x, i.e. (xor x, -1) + no borrow
if (isAllOnesOrAllOnesSplat(N0))
if (!IsSigned && isAllOnesOrAllOnesSplat(N0))
return CombineTo(N, DAG.getNode(ISD::XOR, DL, VT, N1, N0),
DAG.getConstant(0, DL, CarryVT));