diff -r 000000000000 -r 6474c204b198 js/src/jit/UnreachableCodeElimination.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit/UnreachableCodeElimination.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,64 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef jit_UnreachableCodeElimination_h
+#define jit_UnreachableCodeElimination_h
+
+#include "jit/MIRGraph.h"
+
+namespace js {
+namespace jit {
+
+class MIRGraph;
+
+class UnreachableCodeElimination
+{
+    typedef Vector<MBasicBlock *, 16, SystemAllocPolicy> BlockList;
+
+    MIRGenerator *mir_;
+    MIRGraph &graph_;
+    uint32_t marked_;
+    bool redundantPhis_;
+    bool rerunAliasAnalysis_;
+    bool disableAliasAnalysis_;
+
+    bool prunePointlessBranchesAndMarkReachableBlocks();
+    void checkDependencyAndRemoveUsesFromUnmarkedBlocks(MDefinition *instr);
+    bool removeUnmarkedBlocksAndClearDominators();
+    bool removeUnmarkedBlocksAndCleanup();
+
+    bool enqueue(MBasicBlock *block, BlockList &list);
+    MBasicBlock *optimizableSuccessor(MBasicBlock *block);
+
+  public:
+    UnreachableCodeElimination(MIRGenerator *mir, MIRGraph &graph)
+      : mir_(mir),
+        graph_(graph),
+        marked_(0),
+        redundantPhis_(false),
+        rerunAliasAnalysis_(false),
+        disableAliasAnalysis_(false)
+    {}
+
+    // Walks the graph and discovers what is reachable. Removes everything else.
+    bool analyze();
+
+    // Removes any blocks that are not marked.  Assumes that these blocks are not
+    // reachable.  The parameter |marked| should be the number of blocks that
+    // are marked.
+    bool removeUnmarkedBlocks(size_t marked);
+
+    // Call this function to prevent alias analysis to run a second time if we
+    // do not need it.
+    void disableAliasAnalysis() {
+        disableAliasAnalysis_ = true;
+    }
+};
+
+} /* namespace jit */
+} /* namespace js */
+
+#endif /* jit_UnreachableCodeElimination_h */