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Another minor simplification: handle setcc (zero_extend x), c -> setcc(x, c')

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21318 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-04-18 04:30:45 +00:00
parent 7467c9b086
commit 4a44c8df19
1 changed files with 45 additions and 0 deletions
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45
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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@ -406,6 +406,51 @@ SDOperand SelectionDAG::getSetCC(ISD::CondCode Cond, MVT::ValueType VT,
case ISD::SETGE: return getConstant((int64_t)C1 >= (int64_t)C2, VT);
}
} else {
// If the LHS is a ZERO_EXTEND and if this is an ==/!= comparison, perform
// the comparison on the input.
if (N1.getOpcode() == ISD::ZERO_EXTEND) {
unsigned InSize = MVT::getSizeInBits(N1.getOperand(0).getValueType());
// If the comparison constant has bits in the upper part, the
// zero-extended value could never match.
if (C2 & (~0ULL << InSize)) {
unsigned VSize = MVT::getSizeInBits(N1.getValueType());
switch (Cond) {
case ISD::SETUGT:
case ISD::SETUGE:
case ISD::SETEQ: return getConstant(0, VT);
case ISD::SETULT:
case ISD::SETULE:
case ISD::SETNE: return getConstant(1, VT);
case ISD::SETGT:
case ISD::SETGE:
// True if the sign bit of C2 is set.
return getConstant((C2 & (1ULL << VSize)) != 0, VT);
case ISD::SETLT:
case ISD::SETLE:
// True if the sign bit of C2 isn't set.
return getConstant((C2 & (1ULL << VSize)) == 0, VT);
default:
break;
}
}
// Otherwise, we can perform the comparison with the low bits.
switch (Cond) {
case ISD::SETEQ:
case ISD::SETNE:
case ISD::SETUGT:
case ISD::SETUGE:
case ISD::SETULT:
case ISD::SETULE:
return getSetCC(Cond, VT, N1.getOperand(0),
getConstant(C2, N1.getOperand(0).getValueType()));
default:
break; // todo, be more careful with signed comparisons
}
}
uint64_t MinVal, MaxVal;
unsigned OperandBitSize = MVT::getSizeInBits(N2C->getValueType(0));
if (ISD::isSignedIntSetCC(Cond)) {