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author | Jakob Stoklund Olesen <stoklund@2pi.dk> | 2011-04-26 22:33:12 +0000 |
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committer | Jakob Stoklund Olesen <stoklund@2pi.dk> | 2011-04-26 22:33:12 +0000 |
commit | 9f4b893b84d9c2b56aa2abc3c96ce1e5ccc465e5 (patch) | |
tree | c5bf2921106ae502b478c1373c07131d93d855c1 /lib | |
parent | d5c7f7cb5e15a7382cd163cb191db898510226c8 (diff) | |
download | llvm-9f4b893b84d9c2b56aa2abc3c96ce1e5ccc465e5.tar.gz llvm-9f4b893b84d9c2b56aa2abc3c96ce1e5ccc465e5.tar.bz2 llvm-9f4b893b84d9c2b56aa2abc3c96ce1e5ccc465e5.tar.xz |
Add a safe-guard against repeated splitting for some rare cases.
The number of blocks covered by a live range must be strictly decreasing when
splitting, otherwise we can't allow repeated splitting.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130249 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
-rw-r--r-- | lib/CodeGen/RegAllocGreedy.cpp | 18 | ||||
-rw-r--r-- | lib/CodeGen/SplitKit.cpp | 23 | ||||
-rw-r--r-- | lib/CodeGen/SplitKit.h | 5 |
3 files changed, 43 insertions, 3 deletions
diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp index b150582da6..d57bc88a13 100644 --- a/lib/CodeGen/RegAllocGreedy.cpp +++ b/lib/CodeGen/RegAllocGreedy.cpp @@ -921,6 +921,7 @@ void RAGreedy::splitAroundRegion(LiveInterval &VirtReg, SmallVector<unsigned, 8> IntvMap; SE->finish(&IntvMap); LRStage.resize(MRI->getNumVirtRegs()); + unsigned OrigBlocks = SA->getNumThroughBlocks() + SA->getUseBlocks().size(); // Sort out the new intervals created by splitting. We get four kinds: // - Remainder intervals should not be split again. @@ -941,9 +942,20 @@ void RAGreedy::splitAroundRegion(LiveInterval &VirtReg, continue; } - // Other intervals are treated as new. This includes the main interval, - // local intervals created for blocks with multiple uses, and anything - // created by DCE. + // Main interval. Allow repeated splitting as long as the number of live + // blocks is strictly decreasing. + if (IntvMap[i] == MainIntv) { + if (SA->countLiveBlocks(LREdit.get(i)) >= OrigBlocks) { + DEBUG(dbgs() << "Main interval covers the same " << OrigBlocks + << " blocks as original.\n"); + // Don't allow repeated splitting as a safe guard against looping. + LRStage[Reg] = RS_Global; + } + continue; + } + + // Other intervals are treated as new. This includes local intervals created + // for blocks with multiple uses, and anything created by DCE. } if (VerifyEnabled) diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp index c6e1bd57bd..427ef94ad7 100644 --- a/lib/CodeGen/SplitKit.cpp +++ b/lib/CodeGen/SplitKit.cpp @@ -221,6 +221,29 @@ bool SplitAnalysis::calcLiveBlockInfo() { return true; } +unsigned SplitAnalysis::countLiveBlocks(const LiveInterval *cli) const { + if (cli->empty()) + return 0; + LiveInterval *li = const_cast<LiveInterval*>(cli); + LiveInterval::iterator LVI = li->begin(); + LiveInterval::iterator LVE = li->end(); + unsigned Count = 0; + + // Loop over basic blocks where li is live. + MachineFunction::const_iterator MFI = LIS.getMBBFromIndex(LVI->start); + SlotIndex Stop = LIS.getMBBEndIdx(MFI); + for (;;) { + ++Count; + LVI = li->advanceTo(LVI, Stop); + if (LVI == LVE) + return Count; + do { + ++MFI; + Stop = LIS.getMBBEndIdx(MFI); + } while (Stop <= LVI->start); + } +} + bool SplitAnalysis::isOriginalEndpoint(SlotIndex Idx) const { unsigned OrigReg = VRM.getOriginal(CurLI->reg); const LiveInterval &Orig = LIS.getInterval(OrigReg); diff --git a/lib/CodeGen/SplitKit.h b/lib/CodeGen/SplitKit.h index cccaace6f9..2ae760a58d 100644 --- a/lib/CodeGen/SplitKit.h +++ b/lib/CodeGen/SplitKit.h @@ -150,6 +150,11 @@ public: /// getThroughBlocks - Return the set of through blocks. const BitVector &getThroughBlocks() const { return ThroughBlocks; } + /// countLiveBlocks - Return the number of blocks where li is live. + /// This is guaranteed to return the same number as getNumThroughBlocks() + + /// getUseBlocks().size() after calling analyze(li). + unsigned countLiveBlocks(const LiveInterval *li) const; + typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet; /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from |