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
diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp
index b150582..d57bc88 100644
--- a/lib/CodeGen/RegAllocGreedy.cpp
+++ b/lib/CodeGen/RegAllocGreedy.cpp
@@ -921,6 +921,7 @@
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 @@
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)