diff -r 000000000000 -r 6474c204b198 js/src/jit/BytecodeAnalysis.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit/BytecodeAnalysis.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,80 @@
+/* -*- 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_BytecodeAnalysis_h
+#define jit_BytecodeAnalysis_h
+
+#include "jsscript.h"
+#include "jit/IonAllocPolicy.h"
+#include "js/Vector.h"
+
+namespace js {
+namespace jit {
+
+// Basic information about bytecodes in the script.  Used to help baseline compilation.
+struct BytecodeInfo
+{
+    static const uint16_t MAX_STACK_DEPTH = 0xffffU;
+    uint16_t stackDepth;
+    bool initialized : 1;
+    bool jumpTarget : 1;
+    bool jumpFallthrough : 1;
+    bool fallthrough : 1;
+
+    // If true, this is a JSOP_LOOPENTRY op inside a catch or finally block.
+    bool loopEntryInCatchOrFinally : 1;
+
+    void init(unsigned depth) {
+        JS_ASSERT(depth <= MAX_STACK_DEPTH);
+        JS_ASSERT_IF(initialized, stackDepth == depth);
+        initialized = true;
+        stackDepth = depth;
+    }
+};
+
+class BytecodeAnalysis
+{
+    JSScript *script_;
+    Vector<BytecodeInfo, 0, IonAllocPolicy> infos_;
+
+    bool usesScopeChain_;
+    bool hasTryFinally_;
+    bool hasSetArg_;
+
+  public:
+    explicit BytecodeAnalysis(TempAllocator &alloc, JSScript *script);
+
+    bool init(TempAllocator &alloc, GSNCache &gsn);
+
+    BytecodeInfo &info(jsbytecode *pc) {
+        JS_ASSERT(infos_[script_->pcToOffset(pc)].initialized);
+        return infos_[script_->pcToOffset(pc)];
+    }
+
+    BytecodeInfo *maybeInfo(jsbytecode *pc) {
+        if (infos_[script_->pcToOffset(pc)].initialized)
+            return &infos_[script_->pcToOffset(pc)];
+        return nullptr;
+    }
+
+    bool usesScopeChain() const {
+        return usesScopeChain_;
+    }
+
+    bool hasTryFinally() const {
+        return hasTryFinally_;
+    }
+
+    bool hasSetArg() const {
+        return hasSetArg_;
+    }
+};
+
+
+} // namespace jit
+} // namespace js
+
+#endif /* jit_BytecodeAnalysis_h */