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Implement InstCombine/add.ll:test28, transforming C1-(X+C2) --> (C1-C2)-X. 

This occurs several dozen times in specint2k, particularly in crafty and gcc
apparently.

llvm-svn: 21136
This commit is contained in:
Chris Lattner 2005-04-07 16:28:01 +00:00
parent dd83183c1e
commit c7f3c1a00e
1 changed files with 8 additions and 2 deletions
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10
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -795,10 +795,16 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
if (Op1I->getOpcode() == Instruction::Add &&
!Op0->getType()->isFloatingPoint()) {
if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y
if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y
return BinaryOperator::createNeg(Op1I->getOperand(1), I.getName());
else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y
else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y
return BinaryOperator::createNeg(Op1I->getOperand(0), I.getName());
else if (ConstantInt *CI1 = dyn_cast<ConstantInt>(I.getOperand(0))) {
if (ConstantInt *CI2 = dyn_cast<ConstantInt>(Op1I->getOperand(1)))
// C1-(X+C2) --> (C1-C2)-X
return BinaryOperator::createSub(ConstantExpr::getSub(CI1, CI2),
Op1I->getOperand(0));
}
}
if (Op1I->hasOneUse()) {