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Only split around a loop if the live range has uses outside the loop periphery.

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Before we would also split around a loop if any peripheral block had multiple
uses. This could cause repeated splitting when splitting a different live range
would insert uses into the periphery.

Now -spiller=inline passes the nightly test suite again.

llvm-svn: 116494
This commit is contained in:
Jakob Stoklund Olesen 2010-10-14 18:26:45 +00:00
parent 467d56737b
commit e0b9dbf91b
1 changed files with 13 additions and 14 deletions
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27
lib/CodeGen/SplitKit.cpp
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@ -213,24 +213,28 @@ const MachineLoop *SplitAnalysis::getBestSplitLoop() {
if (usingLoops_.empty())
return 0;
LoopPtrSet Loops, SecondLoops;
LoopPtrSet Loops;
LoopBlocks Blocks;
BlockPtrSet CriticalExits;
// Find first-class and second class candidate loops.
// We prefer to split around loops where curli is used outside the periphery.
// We split around loops where curli is used outside the periphery.
for (LoopCountMap::const_iterator I = usingLoops_.begin(),
E = usingLoops_.end(); I != E; ++I) {
const MachineLoop *Loop = I->first;
getLoopBlocks(Loop, Blocks);
LoopPtrSet *LPS = 0;
switch(analyzeLoopPeripheralUse(Blocks)) {
case OutsideLoop:
LPS = &Loops;
break;
case MultiPeripheral:
LPS = &SecondLoops;
// FIXME: We could split a live range with multiple uses in a peripheral
// block and still make progress. However, it is possible that splitting
// another live range will insert copies into a peripheral block, and
// there is a small chance we can enter an infinity loop, inserting copies
// forever.
// For safety, stick to splitting live ranges with uses outside the
// periphery.
DEBUG(dbgs() << " multiple peripheral uses in " << *Loop);
break;
case ContainedInLoop:
DEBUG(dbgs() << " contained in " << *Loop);
@ -246,16 +250,11 @@ const MachineLoop *SplitAnalysis::getBestSplitLoop() {
if (!canSplitCriticalExits(Blocks, CriticalExits))
continue;
// This is a possible split.
assert(LPS);
LPS->insert(Loop);
Loops.insert(Loop);
}
DEBUG(dbgs() << " getBestSplitLoop found " << Loops.size() << " + "
<< SecondLoops.size() << " candidate loops.\n");
// If there are no first class loops available, look at second class loops.
if (Loops.empty())
Loops = SecondLoops;
DEBUG(dbgs() << " getBestSplitLoop found " << Loops.size()
<< " candidate loops.\n");
if (Loops.empty())
return 0;