From 75899aab3574022d3809614200521b9827f74293 Mon Sep 17 00:00:00 2001
From: Alexey Samsonov <vonosmas@gmail.com>
Date: Wed, 3 Sep 2014 18:11:48 +0000
Subject: [PATCH] Fix downcasts of unaligned empty/tombstone DenseMap keys for
 DenseMap<AssertVH<T>, Foo>.

Test Plan: llvm regression test suite

Reviewers: chandlerc, rsmith

Reviewed By: rsmith

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D4976

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217058 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/IR/ValueHandle.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/llvm/IR/ValueHandle.h b/include/llvm/IR/ValueHandle.h
index aa29b2ed690..1371da5a6c6 100644
--- a/include/llvm/IR/ValueHandle.h
+++ b/include/llvm/IR/ValueHandle.h
@@ -189,6 +189,7 @@ class AssertingVH
   : public ValueHandleBase
 #endif
   {
+  friend struct DenseMapInfo<AssertingVH<ValueTy> >;
 
 #ifndef NDEBUG
   ValueTy *getValPtr() const {
@@ -248,11 +249,19 @@ struct DenseMapInfo<AssertingVH<T> > {
   static unsigned getHashValue(const AssertingVH<T> &Val) {
     return PointerInfo::getHashValue(Val);
   }
+#ifndef NDEBUG
+  static bool isEqual(const AssertingVH<T> &LHS, const AssertingVH<T> &RHS) {
+    // Avoid downcasting AssertingVH<T> to T*, as empty/tombstone keys may not
+    // be properly aligned pointers to T*.
+    return LHS.ValueHandleBase::getValPtr() == RHS.ValueHandleBase::getValPtr();
+  }
+#else
   static bool isEqual(const AssertingVH<T> &LHS, const AssertingVH<T> &RHS) {
     return LHS == RHS;
   }
+#endif
 };
-  
+
 template <typename T>
 struct isPodLike<AssertingVH<T> > {
 #ifdef NDEBUG