From a3b666ac4a0975712f1612599727a75eb44e8ac6 Mon Sep 17 00:00:00 2001
From: Anna Zaks <ganna@apple.com>
Date: Tue, 20 Mar 2012 22:56:27 +0000
Subject: [PATCH] Make sure ImmutableSet never inserts Tombstone/Entry into
 DenseMap.

ImmutAVLTree uses random unsigned values as keys into a DenseMap,
which could possibly happen to be the same value as the Tombstone or
Entry keys in the DenseMap.

Test case is hard to come up with. We randomly get failures on the
internal static analyzer bot, which most likely hits this issue
(hard to be 100% sure without the full stack).

llvm-svn: 153148
---
 llvm/include/llvm/ADT/ImmutableSet.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/llvm/include/llvm/ADT/ImmutableSet.h b/llvm/include/llvm/ADT/ImmutableSet.h
index 2926462fa81b..89b164819d37 100644
--- a/llvm/include/llvm/ADT/ImmutableSet.h
+++ b/llvm/include/llvm/ADT/ImmutableSet.h
@@ -347,7 +347,7 @@ public:
       if (prev)
         prev->next = next;
       else
-        factory->Cache[computeDigest()] = next;
+        factory->Cache[factory->maskCacheIndex(computeDigest())] = next;
     }
     
     // We need to clear the mutability bit in case we are
@@ -429,6 +429,11 @@ protected:
   TreeTy*         getRight(TreeTy* T) const { return T->getRight(); }
   value_type_ref  getValue(TreeTy* T) const { return T->value; }
 
+  // Make sure the index is not the Tombstone or Entry key of the DenseMap.
+  static inline unsigned maskCacheIndex(unsigned I) {
+	return (I & ~0x02);
+  }
+
   unsigned incrementHeight(TreeTy* L, TreeTy* R) const {
     unsigned hl = getHeight(L);
     unsigned hr = getHeight(R);
@@ -611,7 +616,7 @@ public:
     // Search the hashtable for another tree with the same digest, and
     // if find a collision compare those trees by their contents.
     unsigned digest = TNew->computeDigest();
-    TreeTy *&entry = Cache[digest];
+    TreeTy *&entry = Cache[maskCacheIndex(digest)];
     do {
       if (!entry)
         break;