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Add micro-optimization which allows us to fold imm into cmp. This allows us to save 1 word (sometimes) and reduce register pressure.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93551 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Anton Korobeynikov 2010-01-15 21:18:02 +00:00
parent 3af4a0b4cb
commit 0c1ba91a54
1 changed files with 32 additions and 0 deletions
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32
lib/Target/MSP430/MSP430ISelLowering.cpp
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@ -675,21 +675,53 @@ static SDValue EmitCMP(SDValue &LHS, SDValue &RHS, SDValue &TargetCC,
case ISD::SETULE:
std::swap(LHS, RHS); // FALLTHROUGH
case ISD::SETUGE:
// Turn lhs u>= rhs with lhs constant into rhs u< lhs+1, this allows us to
// fold constant into instruction.
if (const ConstantSDNode * C = dyn_cast<ConstantSDNode>(LHS)) {
LHS = RHS;
RHS = DAG.getConstant(C->getSExtValue() + 1, C->getValueType(0));
TCC = MSP430CC::COND_LO;
break;
}
TCC = MSP430CC::COND_HS; // aka COND_C
break;
case ISD::SETUGT:
std::swap(LHS, RHS); // FALLTHROUGH
case ISD::SETULT:
// Turn lhs u< rhs with lhs constant into rhs u>= lhs+1, this allows us to
// fold constant into instruction.
if (const ConstantSDNode * C = dyn_cast<ConstantSDNode>(LHS)) {
LHS = RHS;
RHS = DAG.getConstant(C->getSExtValue() + 1, C->getValueType(0));
TCC = MSP430CC::COND_HS;
break;
}
TCC = MSP430CC::COND_LO; // aka COND_NC
break;
case ISD::SETLE:
std::swap(LHS, RHS); // FALLTHROUGH
case ISD::SETGE:
// Turn lhs >= rhs with lhs constant into rhs < lhs+1, this allows us to
// fold constant into instruction.
if (const ConstantSDNode * C = dyn_cast<ConstantSDNode>(LHS)) {
LHS = RHS;
RHS = DAG.getConstant(C->getSExtValue() + 1, C->getValueType(0));
TCC = MSP430CC::COND_L;
break;
}
TCC = MSP430CC::COND_GE;
break;
case ISD::SETGT:
std::swap(LHS, RHS); // FALLTHROUGH
case ISD::SETLT:
// Turn lhs < rhs with lhs constant into rhs >= lhs+1, this allows us to
// fold constant into instruction.
if (const ConstantSDNode * C = dyn_cast<ConstantSDNode>(LHS)) {
LHS = RHS;
RHS = DAG.getConstant(C->getSExtValue() + 1, C->getValueType(0));
TCC = MSP430CC::COND_GE;
break;
}
TCC = MSP430CC::COND_L;
break;
}