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Handle an empty dupli.

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This can happen if the original interval has been broken into two disconnected
parts. Ideally, we should be able to detect when the graph is disconnected and
create separate intervals, but that code is not implemented yet.

Example:

Two basic blocks are both branching to a loop header. Our interval is defined in
both basic blocks, and live into the loop along both edges.

We decide to split the interval around the loop. The interval is split into an
inside part and an outside part. The outside part now has two disconnected
segments, one in each basic block.

If we later decide to split the outside interval into single blocks, we get one
interval per basic block and an empty dupli for the remainder.

llvm-svn: 110976
This commit is contained in:
Jakob Stoklund Olesen 2010-08-12 23:02:57 +00:00
parent f8957964f7
commit 2dc2440b42
1 changed files with 8 additions and 2 deletions
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10
lib/CodeGen/SplitKit.cpp
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@ -674,8 +674,14 @@ void SplitEditor::rewrite() {
// dupli_ goes in last, after rewriting.
if (dupli_) {
dupli_->RenumberValues(lis_);
intervals_.push_back(dupli_);
if (dupli_->empty()) {
DEBUG(dbgs() << " dupli became empty?\n");
lis_.removeInterval(dupli_->reg);
dupli_ = 0;
} else {
dupli_->RenumberValues(lis_);
intervals_.push_back(dupli_);
}
}
// Calculate spill weight and allocation hints for new intervals.