Reset StringMap's NumTombstones on clears and rehashes.

StringMap was not properly updating NumTombstones after a clear or rehash.

This was not fatal until now because the table was growing faster than
NumTombstones could, but with the previous change of preventing infinite
growth of the table the invariant (NumItems + NumTombstones <= NumBuckets)
stopped being observed, causing infinite loops in certain situations.

Patch by José Fonseca!

llvm-svn: 128567

2 files changed, 6 insertions, 0 deletions

diff --git a/llvm/include/llvm/ADT/StringMap.h b/llvm/include/llvm/ADT/StringMap.h
index f3d6b9f4849..907c72d685e 100644
--- a/llvm/include/llvm/ADT/StringMap.h
+++ b/llvm/include/llvm/ADT/StringMap.h
@@ -329,6 +329,7 @@ public:
       --NumTombstones;
     Bucket.Item = KeyValue;
     ++NumItems;
+    assert(NumItems + NumTombstones <= NumBuckets);
 
     RehashTable();
     return true;
@@ -348,6 +349,7 @@ public:
     }
 
     NumItems = 0;
+    NumTombstones = 0;
   }
 
   /// GetOrCreateValue - Look up the specified key in the table.  If a value
@@ -367,6 +369,7 @@ public:
     if (Bucket.Item == getTombstoneVal())
       --NumTombstones;
     ++NumItems;
+    assert(NumItems + NumTombstones <= NumBuckets);
 
     // Fill in the bucket for the hash table.  The FullHashValue was already
     // filled in by LookupBucketFor.
diff --git a/llvm/lib/Support/StringMap.cpp b/llvm/lib/Support/StringMap.cpp
index f193aa42a44..a1ac512fa24 100644
--- a/llvm/lib/Support/StringMap.cpp
+++ b/llvm/lib/Support/StringMap.cpp
@@ -169,6 +169,8 @@ StringMapEntryBase *StringMapImpl::RemoveKey(StringRef Key) {
   TheTable[Bucket].Item = getTombstoneVal();
   --NumItems;
   ++NumTombstones;
+  assert(NumItems + NumTombstones <= NumBuckets);
+
   return Result;
 }
 
@@ -224,4 +226,5 @@ void StringMapImpl::RehashTable() {
   
   TheTable = NewTableArray;
   NumBuckets = NewSize;
+  NumTombstones = 0;
 }