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Implement Reassociate/mul-neg-add.ll
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21788 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -614,6 +614,18 @@ void Reassociate::ReassociateBB(BasicBlock *BB) {
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// sorted form, optimize it globally if possible.
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OptimizeExpression(I->getOpcode(), Ops);
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// We want to sink immediates as deeply as possible except in the case where
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// this is a multiply tree used only by an add, and the immediate is a -1.
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// In this case we reassociate to put the negation on the outside so that we
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// can fold the negation into the add: (-X)*Y + Z -> Z-X*Y
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if (I->getOpcode() == Instruction::Mul && I->hasOneUse() &&
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cast<Instruction>(I->use_back())->getOpcode() == Instruction::Add &&
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isa<ConstantInt>(Ops.back().Op) &&
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cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
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Ops.insert(Ops.begin(), Ops.back());
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Ops.pop_back();
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}
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DEBUG(std::cerr << "RAOut:\t"; PrintOps(I->getOpcode(), Ops, BB);
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std::cerr << "\n");
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