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Add ability to transform (x - (y - z)) into (x + (z - y))

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llvm-svn: 2566
This commit is contained in:
Chris Lattner 2002-05-09 01:29:19 +00:00
parent 890652c8a2
commit 172488eb68
1 changed files with 13 additions and 0 deletions
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13
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -180,6 +180,19 @@ Instruction *InstCombiner::visitSub(BinaryOperator *I) {
if (Value *V = dyn_castNegInst(Op1))
return BinaryOperator::create(Instruction::Add, Op0, V);
// Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression is
// not used by anyone else...
//
if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
if (Op1I->use_size() == 1) {
// Swap the two operands of the subexpr...
Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
Op1I->setOperand(0, IIOp1);
Op1I->setOperand(1, IIOp0);
// Create the new top level add instruction...
return BinaryOperator::create(Instruction::Add, Op0, Op1);
}
return 0;
}