diff options
| -rw-r--r-- | polly/lib/Analysis/ScopDetection.cpp | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/polly/lib/Analysis/ScopDetection.cpp b/polly/lib/Analysis/ScopDetection.cpp index d6721302b34..7d2dcbee52a 100644 --- a/polly/lib/Analysis/ScopDetection.cpp +++ b/polly/lib/Analysis/ScopDetection.cpp @@ -309,6 +309,35 @@ bool ScopDetection::addOverApproximatedRegion(Region *AR, // Reject if the surrounding loop does not entirely contain the nonaffine // subregion. + // This can happen because a region can contain BBs that have no path to the + // exit block (Infinite loops, UnreachableInst), but such blocks are never + // part of a loop. + // + // _______________ + // | Loop Header | <-----------. + // --------------- | + // | | + // _______________ ______________ + // | RegionEntry |-----> | RegionExit |-----> + // --------------- -------------- + // | + // _______________ + // | EndlessLoop | <--. + // --------------- | + // | | + // \------------/ + // + // In the example above, the loop (LoopHeader,RegionEntry,RegionExit) is + // neither entirely contained in the region RegionEntry->RegionExit + // (containing RegionEntry,EndlessLoop) nor is the region entirely contained + // in the loop. + // The block EndlessLoop is contained is in the region because + // Region::contains tests whether it is not dominated by RegionExit. This is + // probably to not having to query the PostdominatorTree. + // Instead of an endless loop, a dead end can also be formed by + // UnreachableInst. This case is already caught by isErrorBlock(). We hence + // only have to test whether there is an endless loop not contained in the + // surrounding loop. BasicBlock *BBEntry = AR->getEntry(); Loop *L = LI->getLoopFor(BBEntry); while (L && AR->contains(L)) |
