[LoopInfo] Verify BBMap tracks innermost loops for BBs.

By checking that none of the child loops contain a BB we make sure BBMap
contains the innermost loop defining BB. This invariant was violated in
LoopInterchange and got caught by this assertion.

Reviewers: chandlerc, mzolotukhin, sanjoy, mehdi_amini, efriedma

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D45971

llvm-svn: 330698

include/llvm/Analysis/LoopInfo.h

@@ -178,6 +178,12 @@ public:
     return DenseBlockSet;
   }
 
+  /// Return a direct, immutable handle to the blocks set.
+  const SmallPtrSetImpl<const BlockT *> &getBlocksSet() const {
+    assert(!isInvalid() && "Loop not in a valid state!");
+    return DenseBlockSet;
+  }
+
   /// Return true if this loop is no longer valid.  The only valid use of this
   /// helper is "assert(L.isInvalid())" or equivalent, since IsInvalid is set to
   /// true by the destructor.  In other words, if this accessor returns true,

include/llvm/Analysis/LoopInfoImpl.h

@@ -617,6 +617,15 @@ static void compareLoops(const LoopT *L, const LoopT *OtherL,
   std::vector<BlockT *> OtherBBs = OtherL->getBlocks();
   assert(compareVectors(BBs, OtherBBs) &&
          "Mismatched basic blocks in the loops!");
+
+  const SmallPtrSetImpl<const BlockT *> &BlocksSet = L->getBlocksSet();
+  const SmallPtrSetImpl<const BlockT *> &OtherBlocksSet = L->getBlocksSet();
+  assert(BlocksSet.size() == OtherBlocksSet.size() &&
+         std::all_of(BlocksSet.begin(), BlocksSet.end(),
+                     [&OtherBlocksSet](const BlockT *BB) {
+                       return OtherBlocksSet.count(BB);
+                     }) &&
+         "Mismatched basic blocks in BlocksSets!");
 }
 #endif
 
@@ -636,6 +645,9 @@ void LoopInfoBase<BlockT, LoopT>::verify(
     LoopT *L = Entry.second;
     assert(Loops.count(L) && "orphaned loop");
     assert(L->contains(BB) && "orphaned block");
+    for (LoopT *ChildLoop : *L)
+      assert(!ChildLoop->contains(BB) &&
+             "BBMap should point to the innermost loop containing BB");
   }
 
   // Recompute LoopInfo to verify loops structure.