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Rework this to clarify where the removal of nodes from the queue is 

really happening.  No intended functionality change.

llvm-svn: 159451
This commit is contained in:
Duncan Sands 2012-06-29 19:03:05 +00:00
parent 1db30fc071
commit 9838286d9e
1 changed files with 9 additions and 8 deletions
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17
llvm/lib/Transforms/Scalar/Reassociate.cpp
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@ -667,15 +667,13 @@ void Reassociate::RewriteExprTree(BinaryOperator *I,
/// the new expression into.
SmallVector<BinaryOperator*, 8> NodesToRewrite;
unsigned Opcode = I->getOpcode();
NodesToRewrite.push_back(I);
BinaryOperator *Op = I;
// ExpressionChanged - Non-null if the rewritten expression differs from the
// original in some non-trivial way, requiring the clearing of optional flags.
// Flags are cleared from the operator in ExpressionChanged up to I inclusive.
BinaryOperator *ExpressionChanged = 0;
for (unsigned i = 0; ; ++i) {
BinaryOperator *Op = NodesToRewrite.pop_back_val();
// The last operation (which comes earliest in the IR) is special as both
// operands will come from Ops, rather than just one with the other being
// a subexpression.
@ -746,7 +744,7 @@ void Reassociate::RewriteExprTree(BinaryOperator *I,
// from the original expression then just rewrite the rest of the expression
// into it.
if (BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode)) {
NodesToRewrite.push_back(BO);
Op = BO;
continue;
}
@ -757,19 +755,22 @@ void Reassociate::RewriteExprTree(BinaryOperator *I,
// hard (finding the mimimal number of multiplications needed to realize a
// multiplication expression is NP-complete). Whatever the reason, smart or
// stupid, create a new node if there are none left.
BinaryOperator *NewOp;
if (NodesToRewrite.empty()) {
Constant *Undef = UndefValue::get(I->getType());
BinaryOperator *N = BinaryOperator::Create(Instruction::BinaryOps(Opcode),
Undef, Undef, "", I);
NodesToRewrite.push_back(N);
NewOp = BinaryOperator::Create(Instruction::BinaryOps(Opcode),
Undef, Undef, "", I);
} else {
NewOp = NodesToRewrite.pop_back_val();
}
DEBUG(dbgs() << "RA: " << *Op << '\n');
Op->setOperand(0, NodesToRewrite.back());
Op->setOperand(0, NewOp);
DEBUG(dbgs() << "TO: " << *Op << '\n');
ExpressionChanged = Op;
MadeChange = true;
++NumChanged;
Op = NewOp;
}
// If the expression changed non-trivially then clear out all subclass data