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Fold C ? 0 : 1 to ~C or zext(~C) or trunc(~C) depending the types.

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llvm-svn: 41163
This commit is contained in:
Evan Cheng 2007-08-18 05:57:05 +00:00
parent 40b9999770
commit a65c956119
1 changed files with 14 additions and 3 deletions
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17
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -2249,6 +2249,7 @@ SDOperand DAGCombiner::visitSELECT(SDNode *N) {
ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1);
ConstantSDNode *N2C = dyn_cast<ConstantSDNode>(N2);
MVT::ValueType VT = N->getValueType(0);
MVT::ValueType VT0 = N0.getValueType();
// fold select C, X, X -> X
if (N1 == N2)
@ -2262,15 +2263,25 @@ SDOperand DAGCombiner::visitSELECT(SDNode *N) {
// fold select C, 1, X -> C | X
if (MVT::i1 == VT && N1C && N1C->getValue() == 1)
return DAG.getNode(ISD::OR, VT, N0, N2);
// fold select C, 0, 1 -> ~C
if (MVT::isInteger(VT) && MVT::isInteger(VT0) &&
N1C && N2C && N1C->isNullValue() && N2C->getValue() == 1) {
SDOperand XORNode = DAG.getNode(ISD::XOR, VT0, N0, DAG.getConstant(1, VT0));
if (VT == VT0)
return XORNode;
AddToWorkList(XORNode.Val);
if (MVT::getSizeInBits(VT) > MVT::getSizeInBits(VT0))
return DAG.getNode(ISD::ZERO_EXTEND, VT, XORNode);
return DAG.getNode(ISD::TRUNCATE, VT, XORNode);
}
// fold select C, 0, X -> ~C & X
// FIXME: this should check for C type == X type, not i1?
if (MVT::i1 == VT && N1C && N1C->isNullValue()) {
if (VT == VT0 && N1C && N1C->isNullValue()) {
SDOperand XORNode = DAG.getNode(ISD::XOR, VT, N0, DAG.getConstant(1, VT));
AddToWorkList(XORNode.Val);
return DAG.getNode(ISD::AND, VT, XORNode, N2);
}
// fold select C, X, 1 -> ~C | X
if (MVT::i1 == VT && N2C && N2C->getValue() == 1) {
if (VT == VT0 && N2C && N2C->getValue() == 1) {
SDOperand XORNode = DAG.getNode(ISD::XOR, VT, N0, DAG.getConstant(1, VT));
AddToWorkList(XORNode.Val);
return DAG.getNode(ISD::OR, VT, XORNode, N1);