js/src/methodjit/Retcon.h

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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   4  * ***** BEGIN LICENSE BLOCK *****
   5  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
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   7  * The contents of this file are subject to the Mozilla Public License Version
   8  * 1.1 (the "License"); you may not use this file except in compliance with
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  13  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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  16  *
  17  * The Original Code is Mozilla Jaegermonkey.
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  19  * The Initial Developer of the Original Code is the Mozilla Foundation.
  20  *
  21  * Portions created by the Initial Developer are Copyright (C) 2010
  22  * the Initial Developer. All Rights Reserved.
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  24  * Contributor(s):
  25  *   Andrew Drake <drakedevel@gmail.com>
  26  *
  27  * Alternatively, the contents of this file may be used under the terms of
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  39  * ***** END LICENSE BLOCK ***** */
  40
  41 /*
  42  * Retroactive continuity ("retcon") refers to the retroactive modification
  43  * or reinterpretation of established facts.
  44  */
  45
  46 #if !defined jsjaeger_retcon_h__ && defined JS_METHODJIT
  47 #define jsjaeger_retcon_h__
  48
  49 #include "jscntxt.h"
  50 #include "jsscript.h"
  51 #include "MethodJIT.h"
  52 #include "Compiler.h"
  53
  54 namespace js {
  55 namespace mjit {
  56
  57 /*
  58  * A problem often arises where, for one reason or another, a piece of code
  59  * wants to touch the script->code, but isn't expecting JSOP_TRAP. This allows
  60  * one to temporarily remove JSOP_TRAPs from the instruction stream (without
  61  * copying) and automatically re-add them on scope exit.
  62  */
  63 class AutoScriptRetrapper
  64 {
  65   public:
  66     AutoScriptRetrapper(JSContext *cx1, JSScript *script1) :
  67         cx(cx1), script(script1), traps(cx) {};
  68     ~AutoScriptRetrapper();
  69
  70     bool untrap(jsbytecode *pc);
  71
  72   private:
  73     JSContext *cx;
  74     JSScript *script;
  75     Vector<jsbytecode*> traps;
  76 };
  77
  78 /*
  79  * This class is responsible for sanely re-JITing a script and fixing up
  80  * the world. If you ever change the code associated with a JSScript, or
  81  * otherwise would cause existing JITed code to be incorrect, you /must/ use
  82  * this to invalidate and potentially re-compile the existing JITed code,
  83  * fixing up the stack in the process.
  84  */
  85 class Recompiler {
  86     struct PatchableAddress {
  87         void **location;
  88         CallSite callSite;
  89     };
  90
  91 public:
  92     Recompiler(JSContext *cx, JSScript *script);
  93
  94     bool recompile();
  95
  96 private:
  97     JSContext *cx;
  98     JSScript *script;
  99
 100     PatchableAddress findPatch(JITScript *jit, void **location);
 101     void applyPatch(Compiler& c, PatchableAddress& toPatch);
 102     bool recompile(JSStackFrame *fp, Vector<PatchableAddress> &patches,
 103                    Vector<CallSite> &sites);
 104     bool saveTraps(JITScript *jit, Vector<CallSite> *sites);
 105 };
 106
 107 } /* namespace mjit */
 108 } /* namespace js */
 109
 110 #endif
 111