js/src/jsanalyze.h

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   3 /* ***** BEGIN LICENSE BLOCK *****
   4  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
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   7  * 1.1 (the "License"); you may not use this file except in compliance with
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  12  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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  14  * License.
  15  *
  16  * The Original Code is the Mozilla SpiderMonkey bytecode analysis
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  18  * The Initial Developer of the Original Code is
  19  *   Mozilla Foundation
  20  * Portions created by the Initial Developer are Copyright (C) 2010
  21  * the Initial Developer. All Rights Reserved.
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  37  * ***** END LICENSE BLOCK ***** */
  38
  39 /* Definitions for javascript analysis. */
  40
  41 #ifndef jsanalyze_h___
  42 #define jsanalyze_h___
  43
  44 #include "jsarena.h"
  45 #include "jscntxt.h"
  46 #include "jsscript.h"
  47
  48 struct JSScript;
  49
  50 namespace js {
  51 namespace analyze {
  52
  53 class Script;
  54
  55 /* Information about a bytecode instruction. */
  56 struct Bytecode
  57 {
  58     friend class Script;
  59
  60     /* Whether there are any incoming jumps to this instruction. */
  61     bool jumpTarget : 1;
  62
  63     /* Whether this instruction has been analyzed to get its output defines and stack. */
  64     bool analyzed : 1;
  65
  66     /* Whether this is a catch/finally entry point. */
  67     bool exceptionEntry : 1;
  68
  69     /* Whether this is in a try block. */
  70     bool inTryBlock : 1;
  71
  72     /* Whether this is a method JIT safe point. */
  73     bool safePoint : 1;
  74
  75     /* Stack depth before this opcode. */
  76     uint32 stackDepth;
  77
  78     /*
  79      * The set of locals defined at this point.  This does not include locals which
  80      * were unconditionally defined at an earlier point in the script.
  81      */
  82     uint32 defineCount;
  83     uint32 *defineArray;
  84
  85     Bytecode()
  86     {
  87         PodZero(this);
  88     }
  89
  90   private:
  91     bool mergeDefines(JSContext *cx,
  92                       Script *script, bool initial, uint32 newDepth,
  93                       uint32 *newArray, uint32 newCount);
  94
  95     /* Whether a local variable is in the define set at this bytecode. */
  96     bool isDefined(uint32 slot)
  97     {
  98         JS_ASSERT(analyzed);
  99         for (size_t ind = 0; ind < defineCount; ind++) {
 100             if (defineArray[ind] == slot)
 101                 return true;
 102         }
 103         return false;
 104     }
 105 };
 106
 107 /* Information about a script. */
 108 class Script
 109 {
 110     friend struct Bytecode;
 111
 112     JSScript *script;
 113     Bytecode **code;
 114
 115     /* Maximum number of locals to consider for a script. */
 116     static const unsigned LOCAL_LIMIT = 50;
 117
 118     /* Offsets at which each local becomes unconditionally defined, or a value below. */
 119     uint32 *locals;
 120
 121     static const uint32 LOCAL_USE_BEFORE_DEF = uint32(-1);
 122     static const uint32 LOCAL_CONDITIONALLY_DEFINED = uint32(-2);
 123
 124     bool outOfMemory;
 125     bool hadFailure;
 126     bool usesRval;
 127     bool usesScope;
 128
 129   public:
 130     /* Pool for allocating analysis structures which will not outlive this script. */
 131     JSArenaPool pool;
 132
 133     void analyze(JSContext *cx, JSScript *script);
 134     void destroy();
 135
 136     /*
 137      * For analysis scripts allocated on the stack.  Scripts don't have constructors,
 138      * and must be zeroed out before being used.
 139      */
 140     ~Script() { destroy(); }
 141
 142     /* Whether we ran out of memory during analysis. */
 143     bool OOM() { return outOfMemory; }
 144
 145     /* Whether the script was analyzed successfully. */
 146     bool failed() { return hadFailure; }
 147
 148     /* Whether there are POPV/SETRVAL bytecodes which can write to the frame's rval. */
 149     bool usesReturnValue() const { return usesRval; }
 150
 151     /* Whether there are NAME bytecodes which can access the frame's scope chain. */
 152     bool usesScopeChain() const { return usesScope; }
 153
 154     /* Accessors for bytecode information. */
 155
 156     Bytecode& getCode(uint32 offset) {
 157         JS_ASSERT(offset < script->length);
 158         JS_ASSERT(code[offset]);
 159         return *code[offset];
 160     }
 161     Bytecode& getCode(jsbytecode *pc) { return getCode(pc - script->code); }
 162
 163     Bytecode* maybeCode(uint32 offset) {
 164         JS_ASSERT(offset < script->length);
 165         return code[offset];
 166     }
 167     Bytecode* maybeCode(jsbytecode *pc) { return maybeCode(pc - script->code); }
 168
 169     bool jumpTarget(uint32 offset) {
 170         JS_ASSERT(offset < script->length);
 171         return code[offset] && code[offset]->jumpTarget;
 172     }
 173     bool jumpTarget(jsbytecode *pc) { return jumpTarget(pc - script->code); }
 174
 175     /* Accessors for local variable information. */
 176
 177     unsigned localCount() {
 178         return (script->nfixed >= LOCAL_LIMIT) ? LOCAL_LIMIT : script->nfixed;
 179     }
 180
 181     bool localHasUseBeforeDef(uint32 local) {
 182         JS_ASSERT(local < script->nfixed && !failed());
 183         return local >= localCount() || locals[local] == LOCAL_USE_BEFORE_DEF;
 184     }
 185
 186     /* These return true for variables that may have a use before def. */
 187     bool localDefined(uint32 local, uint32 offset) {
 188         return localHasUseBeforeDef(local) || (locals[local] <= offset) ||
 189             getCode(offset).isDefined(local);
 190     }
 191     bool localDefined(uint32 local, jsbytecode *pc) {
 192         return localDefined(local, pc - script->code);
 193     }
 194
 195   private:
 196     void setOOM(JSContext *cx) {
 197         if (!outOfMemory)
 198             js_ReportOutOfMemory(cx);
 199         outOfMemory = true;
 200         hadFailure = true;
 201     }
 202
 203     inline bool addJump(JSContext *cx, unsigned offset,
 204                         unsigned *currentOffset, unsigned *forwardJump,
 205                         unsigned stackDepth, uint32 *defineArray, unsigned defineCount);
 206
 207     inline void setLocal(uint32 local, uint32 offset);
 208 };
 209
 210 } /* namespace analyze */
 211 } /* namespace js */
 212
 213 #endif // jsanalyze_h___