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Compile this:

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xori r6, r2, 1
        rlwinm r6, r6, 0, 31, 31
        cmpwi cr0, r6, 0
        bne cr0, LBB1_3 ; endif

to this:

        rlwinm r6, r2, 0, 31, 31
        cmpwi cr0, r6, 0
        beq cr0, LBB1_3 ; endif


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26047 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-02-08 02:13:15 +00:00
parent 5819342732
commit 3391bcd434
1 changed files with 26 additions and 0 deletions
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26
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -2544,6 +2544,32 @@ SDOperand DAGCombiner::SimplifySetCC(MVT::ValueType VT, SDOperand N0,
DAG.getConstant(C1 & (~0ULL>>(64-ExtSrcTyBits)),
ExtDstTy),
Cond);
} else if ((N1C->getValue() == 0 || N1C->getValue() == 1) &&
(Cond == ISD::SETEQ || Cond == ISD::SETNE) &&
(N0.getOpcode() == ISD::XOR ||
(N0.getOpcode() == ISD::AND &&
N0.getOperand(0).getOpcode() == ISD::XOR &&
N0.getOperand(1) == N0.getOperand(0).getOperand(1))) &&
isa<ConstantSDNode>(N0.getOperand(1)) &&
cast<ConstantSDNode>(N0.getOperand(1))->getValue() == 1) {
// If this is (X^1) == 0/1, swap the RHS and eliminate the xor. We can
// only do this if the top bits are known zero.
if (TLI.MaskedValueIsZero(N1,
MVT::getIntVTBitMask(N0.getValueType())-1)) {
// Okay, get the un-inverted input value.
SDOperand Val;
if (N0.getOpcode() == ISD::XOR)
Val = N0.getOperand(0);
else {
assert(N0.getOpcode() == ISD::AND &&
N0.getOperand(0).getOpcode() == ISD::XOR);
// ((X^1)&1)^1 -> X & 1
Val = DAG.getNode(ISD::AND, N0.getValueType(),
N0.getOperand(0).getOperand(0), N0.getOperand(1));
}
return DAG.getSetCC(VT, Val, N1,
Cond == ISD::SETEQ ? ISD::SETNE : ISD::SETEQ);
}
}
uint64_t MinVal, MaxVal;