From b3c8febd1ed75b599cd1929b3ec1b7380615bd72 Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Wed, 9 Nov 2011 04:16:01 +0000
Subject: [PATCH] Enhance verifyLoop so that it can reliably verify that every
 block in a loop is reachable from the loop header.

llvm-svn: 144166
---
 llvm/include/llvm/Analysis/LoopInfo.h | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/llvm/include/llvm/Analysis/LoopInfo.h b/llvm/include/llvm/Analysis/LoopInfo.h
index 12cb6c5cc480..535d2055e538 100644
--- a/llvm/include/llvm/Analysis/LoopInfo.h
+++ b/llvm/include/llvm/Analysis/LoopInfo.h
@@ -416,14 +416,26 @@ public:
 #ifndef NDEBUG
     assert(!Blocks.empty() && "Loop header is missing");
 
+    // Setup for using a depth-first iterator to visit every block in the loop.
+    SmallVector<BlockT*, 8> ExitBBs;
+    getExitBlocks(ExitBBs);
+    llvm::SmallPtrSet<BlockT*, 8> VisitSet;
+    VisitSet.insert(ExitBBs.begin(), ExitBBs.end());
+    df_ext_iterator<BlockT*, llvm::SmallPtrSet<BlockT*, 8> >
+        BI = df_ext_begin(getHeader(), VisitSet),
+        BE = df_ext_end(getHeader(), VisitSet);
+
+    // Keep track of the number of BBs visited.
+    unsigned NumVisited = 0;
+
     // Sort the blocks vector so that we can use binary search to do quick
     // lookups.
     SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
     std::sort(LoopBBs.begin(), LoopBBs.end());
 
     // Check the individual blocks.
-    for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) {
-      BlockT *BB = *I;
+    for ( ; BI != BE; ++BI) {
+      BlockT *BB = *BI;
       bool HasInsideLoopSuccs = false;
       bool HasInsideLoopPreds = false;
       SmallVector<BlockT *, 2> OutsideLoopPreds;
@@ -440,7 +452,7 @@ public:
       for (typename InvBlockTraits::ChildIteratorType PI =
            InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB);
            PI != PE; ++PI) {
-        typename InvBlockTraits::NodeType *N = *PI;
+        BlockT *N = *PI;
         if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), N))
           HasInsideLoopPreds = true;
         else
@@ -464,8 +476,12 @@ public:
       assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!");
       assert(BB != getHeader()->getParent()->begin() &&
              "Loop contains function entry block!");
+
+      NumVisited++;
     }
 
+    assert(NumVisited == getNumBlocks() && "Unreachable block in loop");
+
     // Check the subloops.
     for (iterator I = begin(), E = end(); I != E; ++I)
       // Each block in each subloop should be contained within this loop.