diff -r 000000000000 -r 6474c204b198 js/src/jsopcodeinlines.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jsopcodeinlines.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,119 @@
+/* -*- 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 jsopcodeinlines_h
+#define jsopcodeinlines_h
+
+#include "jsopcode.h"
+
+#include "jsscript.h"
+
+namespace js {
+
+static inline unsigned
+GetDefCount(JSScript *script, unsigned offset)
+{
+    jsbytecode *pc = script->offsetToPC(offset);
+
+    /*
+     * Add an extra pushed value for OR/AND opcodes, so that they are included
+     * in the pushed array of stack values for type inference.
+     */
+    switch (JSOp(*pc)) {
+      case JSOP_OR:
+      case JSOP_AND:
+        return 1;
+      case JSOP_PICK:
+        /*
+         * Pick pops and pushes how deep it looks in the stack + 1
+         * items. i.e. if the stack were |a b[2] c[1] d[0]|, pick 2
+         * would pop b, c, and d to rearrange the stack to |a c[0]
+         * d[1] b[2]|.
+         */
+        return pc[1] + 1;
+      default:
+        return StackDefs(script, pc);
+    }
+}
+
+static inline unsigned
+GetUseCount(JSScript *script, unsigned offset)
+{
+    jsbytecode *pc = script->offsetToPC(offset);
+
+    if (JSOp(*pc) == JSOP_PICK)
+        return pc[1] + 1;
+    if (js_CodeSpec[*pc].nuses == -1)
+        return StackUses(script, pc);
+    return js_CodeSpec[*pc].nuses;
+}
+
+static inline JSOp
+ReverseCompareOp(JSOp op)
+{
+    switch (op) {
+      case JSOP_GT:
+        return JSOP_LT;
+      case JSOP_GE:
+        return JSOP_LE;
+      case JSOP_LT:
+        return JSOP_GT;
+      case JSOP_LE:
+        return JSOP_GE;
+      case JSOP_EQ:
+      case JSOP_NE:
+      case JSOP_STRICTEQ:
+      case JSOP_STRICTNE:
+        return op;
+      default:
+        MOZ_ASSUME_UNREACHABLE("unrecognized op");
+    }
+}
+
+static inline JSOp
+NegateCompareOp(JSOp op)
+{
+    switch (op) {
+      case JSOP_GT:
+        return JSOP_LE;
+      case JSOP_GE:
+        return JSOP_LT;
+      case JSOP_LT:
+        return JSOP_GE;
+      case JSOP_LE:
+        return JSOP_GT;
+      case JSOP_EQ:
+        return JSOP_NE;
+      case JSOP_NE:
+        return JSOP_EQ;
+      case JSOP_STRICTNE:
+        return JSOP_STRICTEQ;
+      case JSOP_STRICTEQ:
+        return JSOP_STRICTNE;
+      default:
+        MOZ_ASSUME_UNREACHABLE("unrecognized op");
+    }
+}
+
+class BytecodeRange {
+  public:
+    BytecodeRange(JSContext *cx, JSScript *script)
+      : script(cx, script), pc(script->code()), end(pc + script->length())
+    {}
+    bool empty() const { return pc == end; }
+    jsbytecode *frontPC() const { return pc; }
+    JSOp frontOpcode() const { return JSOp(*pc); }
+    size_t frontOffset() const { return script->pcToOffset(pc); }
+    void popFront() { pc += GetBytecodeLength(pc); }
+
+  private:
+    RootedScript script;
+    jsbytecode *pc, *end;
+};
+
+}
+
+#endif /* jsopcodeinlines_h */