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Swap the operands of a select node if the false (the second) operand is 0. 

For example, this pattern 
(select (setcc lhs, rhs, cc), true, 0)
is transformed to this one:
(select (setcc lhs, rhs, inverse(cc)), 0, true)

This enables MipsDAGToDAGISel::ReplaceUsesWithZeroReg (added in r152280) to
replace 0 with $zero.

llvm-svn: 152285
This commit is contained in:
Akira Hatanaka 2012-03-08 02:14:24 +00:00
parent 3f28ec28d5
commit 7dd7c08419
1 changed files with 35 additions and 0 deletions
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35
llvm/lib/Target/Mips/MipsISelLowering.cpp
View File

@ -576,6 +576,39 @@ static SDValue PerformSETCCCombine(SDNode *N, SelectionDAG& DAG,
return CreateCMovFP(DAG, Cond, True, False, N->getDebugLoc());
}
static SDValue PerformSELECTCombine(SDNode *N, SelectionDAG& DAG,
TargetLowering::DAGCombinerInfo &DCI,
const MipsSubtarget* Subtarget) {
if (DCI.isBeforeLegalizeOps())
return SDValue();
SDValue SetCC = N->getOperand(0);
if ((SetCC.getOpcode() != ISD::SETCC) ||
!SetCC.getOperand(0).getValueType().isInteger())
return SDValue();
SDValue False = N->getOperand(2);
EVT FalseTy = False.getValueType();
if (!FalseTy.isInteger())
return SDValue();
ConstantSDNode *CN = dyn_cast<ConstantSDNode>(False);
if (!CN || CN->getZExtValue())
return SDValue();
const DebugLoc DL = N->getDebugLoc();
ISD::CondCode CC = cast<CondCodeSDNode>(SetCC.getOperand(2))->get();
SDValue True = N->getOperand(1);
SetCC = DAG.getSetCC(DL, SetCC.getValueType(), SetCC.getOperand(0),
SetCC.getOperand(1), ISD::getSetCCInverse(CC, true));
return DAG.getNode(ISD::SELECT, DL, FalseTy, SetCC, False, True);
}
static SDValue PerformANDCombine(SDNode *N, SelectionDAG& DAG,
TargetLowering::DAGCombinerInfo &DCI,
const MipsSubtarget* Subtarget) {
@ -686,6 +719,8 @@ SDValue MipsTargetLowering::PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI)
return PerformDivRemCombine(N, DAG, DCI, Subtarget);
case ISD::SETCC:
return PerformSETCCCombine(N, DAG, DCI, Subtarget);
case ISD::SELECT:
return PerformSELECTCombine(N, DAG, DCI, Subtarget);
case ISD::AND:
return PerformANDCombine(N, DAG, DCI, Subtarget);
case ISD::OR: