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Add folding rules for mul X, 0 and mul X, 2
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2417 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -2,7 +2,7 @@
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//
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// InstructionCombining - Combine instructions to form fewer, simple
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// instructions. This pass does not modify the CFG, and has a tendancy to
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// make instructions dead, so a subsequent DCE pass is useful.
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// make instructions dead, so a subsequent DIE pass is useful.
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//
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// This pass combines things like:
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// %Y = add int 1, %X
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@ -75,8 +75,7 @@ namespace {
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//
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static bool SimplifyBinOp(BinaryOperator *I) {
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if (isa<Constant>(I->getOperand(0)) && !isa<Constant>(I->getOperand(1)))
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if (!I->swapOperands())
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return true;
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return !I->swapOperands();
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return false;
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}
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@ -146,6 +145,17 @@ Instruction *InstCombiner::visitMul(BinaryOperator *I) {
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I->replaceAllUsesWith(Op1);
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return I;
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} else if (I->getType()->isIntegral() &&
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cast<ConstantInt>(Op2)->equalsInt(2)) {
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// Convert 'mul int %X, 2' to 'add int %X, %X'
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return BinaryOperator::create(Instruction::Add, Op1, Op1, I->getName());
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} else if (Op2->isNullValue()) {
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// Eliminate 'mul int %X, 0'
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AddUsesToWorkList(I); // Add all modified instrs to worklist
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I->replaceAllUsesWith(Op2); // Set this value to zero directly
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return I;
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}
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}
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