diff options
Diffstat (limited to 'lib/CodeGen')
-rw-r--r-- | lib/CodeGen/SplitKit.cpp | 27 |
1 files changed, 13 insertions, 14 deletions
diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp index 30f9600..2ab7fa8 100644 --- a/lib/CodeGen/SplitKit.cpp +++ b/lib/CodeGen/SplitKit.cpp @@ -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; |