@@ -1,3 +1,18 @@
+2020-06-27  Saam Barati  <sbarati@apple.com>
+
+        BytecodeBasicBlock::addSuccessor should check if the  successor already exists
+        https://bugs.webkit.org/show_bug.cgi?id=213670
+
+        Reviewed by Yusuke Suzuki.
+
+        It makes it nicer for algorithms using BytecodeGraph to not have to consider
+        whether or not there are duplicates in the successor list. Also, because of
+        this, bytecode liveness was doing extra work since it walked the successor list,
+        including any duplicates in it.
+
+        * bytecode/BytecodeBasicBlock.h:
+        (JSC::BytecodeBasicBlock::addSuccessor):
+
 2020-06-27  Saam Barati  <sbarati@apple.com>
 
         Change bytecode dumping to dump the bytecode control flow graph
 
@@ -77,7 +77,11 @@ class BytecodeBasicBlock {
     template<typename Block> static BasicBlockVector computeImpl(Block* codeBlock, const InstructionStream& instructions);
     void shrinkToFit();
 
-    void addSuccessor(BytecodeBasicBlock& block) { m_successors.append(block.index()); }
+    void addSuccessor(BytecodeBasicBlock& block)
+    {
+        if (!m_successors.contains(block.index()))
+            m_successors.append(block.index());
+    }
 
     inline void addLength(unsigned);