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Implement Reassociate/mul-neg-add.ll

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21788 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-05-08 21:41:35 +00:00
parent 22d06312a9
commit 44b8c7d5d3
1 changed files with 12 additions and 0 deletions
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12
lib/Transforms/Scalar/Reassociate.cpp
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@ -614,6 +614,18 @@ void Reassociate::ReassociateBB(BasicBlock *BB) {
// sorted form, optimize it globally if possible.
OptimizeExpression(I->getOpcode(), Ops);
// We want to sink immediates as deeply as possible except in the case where
// this is a multiply tree used only by an add, and the immediate is a -1.
// In this case we reassociate to put the negation on the outside so that we
// can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
if (I->getOpcode() == Instruction::Mul && I->hasOneUse() &&
cast<Instruction>(I->use_back())->getOpcode() == Instruction::Add &&
isa<ConstantInt>(Ops.back().Op) &&
cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
Ops.insert(Ops.begin(), Ops.back());
Ops.pop_back();
}
DEBUG(std::cerr << "RAOut:\t"; PrintOps(I->getOpcode(), Ops, BB);
std::cerr << "\n");