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Fix a reassociate crash on sozefx when compiling with dragonegg+gcc-4.7 due to
the optimizers producing a multiply expression with more multiplications than the original (!). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159426 91177308-0d34-0410-b5e6-96231b3b80d8
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@@ -674,8 +674,6 @@ void Reassociate::RewriteExprTree(BinaryOperator *I,
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// Flags are cleared from the operator in ExpressionChanged up to I inclusive.
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BinaryOperator *ExpressionChanged = 0;
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for (unsigned i = 0; ; ++i) {
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assert(!NodesToRewrite.empty() &&
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"Optimized expressions has more nodes than original!");
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BinaryOperator *Op = NodesToRewrite.pop_back_val();
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// The last operation (which comes earliest in the IR) is special as both
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@@ -753,9 +751,19 @@ void Reassociate::RewriteExprTree(BinaryOperator *I,
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}
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// Otherwise, grab a spare node from the original expression and use that as
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// the left-hand side.
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assert(!NodesToRewrite.empty() &&
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"Optimized expressions has more nodes than original!");
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// the left-hand side. If there are no nodes left then the optimizers made
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// an expression with more nodes than the original! This usually means that
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// they did something stupid but it might mean that the problem was just too
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// hard (finding the mimimal number of multiplications needed to realize a
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// multiplication expression is NP-complete). Whatever the reason, smart or
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// stupid, create a new node if there are none left.
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if (NodesToRewrite.empty()) {
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Constant *Undef = UndefValue::get(I->getType());
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BinaryOperator *N = BinaryOperator::Create(Instruction::BinaryOps(Opcode),
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Undef, Undef, "", I);
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NodesToRewrite.push_back(N);
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}
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DEBUG(dbgs() << "RA: " << *Op << '\n');
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Op->setOperand(0, NodesToRewrite.back());
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DEBUG(dbgs() << "TO: " << *Op << '\n');
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