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This patch does two things. First, it canonicalizes 'X >= C' -> 'X > C-1' 

(likewise for <= >=u >=u).

Second, it implements a special case hack to turn 'X gtu SINTMAX' -> 'X lt 0'

On powerpc, for example, this changes this:

        lis r2, 32767
        ori r2, r2, 65535
        cmplw cr0, r3, r2
        bgt .LBB_test_2

into:

        cmpwi cr0, r3, 0
        blt .LBB_test_2

llvm-svn: 21142
This commit is contained in:
Chris Lattner 2005-04-07 18:14:58 +00:00
parent 31f5e2f73f
commit 6b03a0cba1
1 changed files with 49 additions and 7 deletions
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56
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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@ -375,9 +375,10 @@ SDOperand SelectionDAG::getSetCC(ISD::CondCode Cond, MVT::ValueType VT,
case ISD::SETTRUE2: return getConstant(1, VT);
}
if (ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1.Val))
if (ConstantSDNode *N2C = dyn_cast<ConstantSDNode>(N2.Val)) {
uint64_t C1 = N1C->getValue(), C2 = N2C->getValue();
if (ConstantSDNode *N2C = dyn_cast<ConstantSDNode>(N2.Val)) {
uint64_t C2 = N2C->getValue();
if (ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1.Val)) {
uint64_t C1 = N1C->getValue();
// Sign extend the operands if required
if (ISD::isSignedIntSetCC(Cond)) {
@ -398,11 +399,52 @@ SDOperand SelectionDAG::getSetCC(ISD::CondCode Cond, MVT::ValueType VT,
case ISD::SETLE: return getConstant((int64_t)C1 <= (int64_t)C2, VT);
case ISD::SETGE: return getConstant((int64_t)C1 >= (int64_t)C2, VT);
}
} else {
// Ensure that the constant occurs on the RHS.
Cond = ISD::getSetCCSwappedOperands(Cond);
std::swap(N1, N2);
} else if (1) {
uint64_t MinVal, MaxVal;
unsigned OperandBitSize = MVT::getSizeInBits(N2C->getValueType(0));
if (ISD::isSignedIntSetCC(Cond)) {
MinVal = 1ULL << (OperandBitSize-1);
if (OperandBitSize != 1) // Avoid X >> 64, which is undefined.
MaxVal = ~0ULL >> (65-OperandBitSize);
else
MaxVal = 0;
} else {
MinVal = 0;
MaxVal = ~0ULL >> (64-OperandBitSize);
}
// Canonicalize GE/LE comparisons to use GT/LT comparisons.
if (Cond == ISD::SETGE || Cond == ISD::SETUGE) {
if (C2 == MinVal) return getConstant(1, VT); // X >= MIN --> true
--C2; // X >= C1 --> X > (C1-1)
Cond = (Cond == ISD::SETGE) ? ISD::SETGT : ISD::SETUGT;
N2 = getConstant(C2, N2.getValueType());
N2C = cast<ConstantSDNode>(N2.Val);
}
if (Cond == ISD::SETLE || Cond == ISD::SETULE) {
if (C2 == MaxVal) return getConstant(1, VT); // X <= MAX --> true
++C2; // X <= C1 --> X < (C1+1)
Cond = (Cond == ISD::SETLE) ? ISD::SETLT : ISD::SETULT;
N2 = getConstant(C2, N2.getValueType());
N2C = cast<ConstantSDNode>(N2.Val);
}
// If we have "setcc X, C1", check to see if we can shrink the immediate
// by changing cc.
// SETUGT X, SINTMAX -> SETLT X, 0
if (Cond == ISD::SETUGT && OperandBitSize != 1 &&
C2 == (~0ULL >> (65-OperandBitSize)))
return getSetCC(ISD::SETLT, VT, N1, getConstant(0, N2.getValueType()));
// FIXME: Implement the rest of these.
}
} else if (isa<ConstantSDNode>(N1.Val)) {
// Ensure that the constant occurs on the RHS.
return getSetCC(ISD::getSetCCSwappedOperands(Cond), VT, N2, N1);
}
if (ConstantFPSDNode *N1C = dyn_cast<ConstantFPSDNode>(N1.Val))
if (ConstantFPSDNode *N2C = dyn_cast<ConstantFPSDNode>(N2.Val)) {