Fix maxLoopDepth computation in ScopInfo

[dpeixott]

Summary

The max loop depth was incorrectly computed for scops that contain a
block from a loop but do not contain the entire loop. We need to
check that the full loop is contained in the block when computing
the max loop depth.

[jdoerfert]

LGTM

[grosser]

Yes, this looks good. I wonder in which context you run into this? Is it possible to provide a test case that covers this?

[grosser]

Also, the commit message is slightly inaccurate:

We need to check that the full loop is contained in the block when computing

in the _region_

[dpeixott]

Added test case and fixed commit message.

[dpeixott]

Tobi,

I added a test case and also an explanation in the commit message on when we can hit this problem.

These scops occur when a region containing an inner loop is expanded
to include some blocks from the outer loop, but it cannot be fully
expanded to contain the outer loop because the region containing the
outer loop is invalid.

lib/Analysis/ScopInfo.cpp

bool Scop::buildAliasGroups(AliasAnalysis &AA) {
 
   return Valid;
 }
 
 static unsigned getMaxLoopDepthInRegion(const Region &R, LoopInfo &LI) {
   unsigned MinLD = INT_MAX, MaxLD = 0;
   for (BasicBlock *BB : R.blocks()) {
     if (Loop *L = LI.getLoopFor(BB)) {
+      if (!R.contains(L))
+        continue;
       unsigned LD = L->getLoopDepth();
       MinLD = std::min(MinLD, LD);
       MaxLD = std::max(MaxLD, LD);
     }
   }
 
   // Handle the case that there is no loop in the SCoP first.
   if (MaxLD == 0)