3 files changed, 19 insertions, 2 deletions
diff --git a/llvm/include/llvm/IR/Constants.h b/llvm/include/llvm/IR/Constants.h
index 1acf5b6cc83..448d82931a6 100644
--- a/llvm/include/llvm/IR/Constants.h
+++ b/llvm/include/llvm/IR/Constants.h
@@ -757,6 +757,12 @@ public:
   /// block must be embedded into a function.
   static BlockAddress *get(BasicBlock *BB);
 
+  /// \brief Lookup an existing \c BlockAddress constant for the given
+  /// BasicBlock.
+  ///
+  /// \returns 0 if \c !BB->hasAddressTaken(), otherwise the \c BlockAddress.
+  static BlockAddress *lookup(const BasicBlock *BB);
+
   /// Transparently provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
 
diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
index 1f6f5ac4270..ecd2cfd9fd1 100644
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -1375,6 +1375,17 @@ BlockAddress::BlockAddress(Function *F, BasicBlock *BB)
   BB->AdjustBlockAddressRefCount(1);
 }
 
+BlockAddress *BlockAddress::lookup(const BasicBlock *BB) {
+  if (!BB->hasAddressTaken())
+    return 0;
+
+  const Function *F = BB->getParent();
+  assert(F != 0 && "Block must have a parent");
+  BlockAddress *BA =
+      F->getContext().pImpl->BlockAddresses.lookup(std::make_pair(F, BB));
+  assert(BA && "Refcount and block address map disagree!");
+  return BA;
+}
 
 // destroyConstant - Remove the constant from the constant table.
 //
diff --git a/llvm/lib/IR/LLVMContextImpl.h b/llvm/lib/IR/LLVMContextImpl.h
index 39e5d778ed6..04338272463 100644
--- a/llvm/lib/IR/LLVMContextImpl.h
+++ b/llvm/lib/IR/LLVMContextImpl.h
@@ -281,8 +281,8 @@ public:
   
   StringMap<ConstantDataSequential*> CDSConstants;
 
-  
-  DenseMap<std::pair<Function*, BasicBlock*> , BlockAddress*> BlockAddresses;
+  DenseMap<std::pair<const Function *, const BasicBlock *>, BlockAddress *>
+    BlockAddresses;
   ConstantUniqueMap<ExprMapKeyType, const ExprMapKeyType&, Type, ConstantExpr>
     ExprConstants;