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437 lines
13 KiB
C++
437 lines
13 KiB
C++
/* -*- Mode: c++; c-basic-offset: 4; tab-width: 40; indent-tabs-mode: nil -*- */
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/* vim: set ts=40 sw=4 et tw=99: */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is the Mozilla SpiderMonkey bytecode analysis
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*
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* The Initial Developer of the Original Code is
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* Mozilla Foundation
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* Portions created by the Initial Developer are Copyright (C) 2010
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either of the GNU General Public License Version 2 or later (the "GPL"),
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* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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/* Definitions for javascript analysis. */
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#ifndef jsanalyze_h___
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#define jsanalyze_h___
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#include "jsarena.h"
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#include "jscntxt.h"
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#include "jsinfer.h"
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#include "jsscript.h"
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struct JSScript;
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/* Forward declaration of downstream register allocations computed for join points. */
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namespace js { namespace mjit { struct RegisterAllocation; } }
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namespace js {
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namespace analyze {
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class Script;
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/* Information about a bytecode instruction. */
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struct Bytecode
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{
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friend class Script;
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/* Whether there are any incoming jumps to this instruction. */
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bool jumpTarget : 1;
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/* Whether there is fallthrough to this instruction from a non-branching instruction. */
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bool fallthrough : 1;
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/* Whether this instruction is the fall through point of a conditional jump. */
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bool jumpFallthrough : 1;
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/* Whether this instruction can be branched to from a switch statement. Implies jumpTarget. */
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bool switchTarget : 1;
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/* Whether this instruction has been analyzed to get its output defines and stack. */
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bool analyzed : 1;
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/* Whether this is a catch/finally entry point. */
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bool exceptionEntry : 1;
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/* Whether this is in a try block. */
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bool inTryBlock : 1;
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/* Method JIT safe point. */
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bool safePoint : 1;
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/* Stack depth before this opcode. */
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uint32 stackDepth;
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/*
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* The set of locals defined at this point. This does not include locals which
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* were unconditionally defined at an earlier point in the script.
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*/
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uint32 defineCount;
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uint32 *defineArray;
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Bytecode(Script *script, unsigned offset)
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{
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PodZero(this);
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}
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private:
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bool mergeDefines(JSContext *cx, Script *script, bool initial,
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uint32 newDepth, uint32 *newArray, uint32 newCount);
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/* Whether a local variable is in the define set at this bytecode. */
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bool isDefined(uint32 slot)
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{
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JS_ASSERT(analyzed);
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for (unsigned ind = 0; ind < defineCount; ind++) {
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if (defineArray[ind] == slot)
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return true;
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}
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return false;
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}
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};
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/* Information about a script. */
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class Script
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{
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friend struct Bytecode;
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JSScript *script;
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Bytecode **codeArray;
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/* Maximum number of locals to consider for a script. */
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static const unsigned LOCAL_LIMIT = 50;
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/* Offsets at which each local becomes unconditionally defined, or a value below. */
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uint32 *locals;
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static const uint32 LOCAL_USE_BEFORE_DEF = uint32(-1);
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static const uint32 LOCAL_CONDITIONALLY_DEFINED = uint32(-2);
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bool outOfMemory;
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bool hadFailure;
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bool usesRval;
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bool usesScope;
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public:
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/* Pool for allocating analysis structures which will not outlive this script. */
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JSArenaPool pool;
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Script();
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~Script();
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void analyze(JSContext *cx, JSScript *script);
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bool OOM() { return outOfMemory; }
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bool failed() { return hadFailure; }
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/* Whether there are POPV/SETRVAL bytecodes which can write to the frame's rval. */
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bool usesReturnValue() const { return usesRval; }
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/* Whether there are NAME bytecodes which can access the frame's scope chain. */
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bool usesScopeChain() const { return usesScope; }
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bool hasAnalyzed() const { return !!codeArray; }
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JSScript *getScript() const { return script; }
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/* Accessors for bytecode information. */
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Bytecode& getCode(uint32 offset) {
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JS_ASSERT(offset < script->length);
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JS_ASSERT(codeArray[offset]);
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return *codeArray[offset];
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}
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Bytecode& getCode(const jsbytecode *pc) { return getCode(pc - script->code); }
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Bytecode* maybeCode(uint32 offset) {
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JS_ASSERT(offset < script->length);
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return codeArray[offset];
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}
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Bytecode* maybeCode(const jsbytecode *pc) { return maybeCode(pc - script->code); }
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bool jumpTarget(uint32 offset) {
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JS_ASSERT(offset < script->length);
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return codeArray[offset] && codeArray[offset]->jumpTarget;
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}
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bool jumpTarget(const jsbytecode *pc) { return jumpTarget(pc - script->code); }
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/* Accessors for local variable information. */
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unsigned localCount() {
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return (script->nfixed >= LOCAL_LIMIT) ? LOCAL_LIMIT : script->nfixed;
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}
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bool localHasUseBeforeDef(uint32 local) {
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JS_ASSERT(!failed());
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return local >= localCount() || locals[local] == LOCAL_USE_BEFORE_DEF;
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}
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/* These return true for variables that may have a use before def. */
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bool localDefined(uint32 local, uint32 offset) {
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return localHasUseBeforeDef(local) || (locals[local] <= offset) ||
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getCode(offset).isDefined(local);
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}
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bool localDefined(uint32 local, jsbytecode *pc) {
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return localDefined(local, pc - script->code);
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}
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bool argEscapes(unsigned arg)
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{
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for (unsigned i = 0; i < script->nClosedArgs; i++) {
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if (arg == script->getClosedArg(i))
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return true;
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}
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return false;
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}
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bool localEscapes(unsigned local)
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{
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if (local >= localCount())
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return true;
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for (unsigned i = 0; i < script->nClosedVars; i++) {
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if (local == script->getClosedVar(i))
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return true;
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}
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return false;
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}
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private:
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void setOOM(JSContext *cx) {
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if (!outOfMemory)
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js_ReportOutOfMemory(cx);
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outOfMemory = true;
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hadFailure = true;
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}
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inline bool addJump(JSContext *cx, unsigned offset,
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unsigned *currentOffset, unsigned *forwardJump,
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unsigned stackDepth, uint32 *defineArray, unsigned defineCount);
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inline void setLocal(uint32 local, uint32 offset);
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};
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static inline unsigned
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GetBytecodeLength(jsbytecode *pc)
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{
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JSOp op = (JSOp)*pc;
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JS_ASSERT(op < JSOP_LIMIT);
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JS_ASSERT(op != JSOP_TRAP);
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if (js_CodeSpec[op].length != -1)
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return js_CodeSpec[op].length;
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return js_GetVariableBytecodeLength(pc);
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}
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static inline unsigned
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GetUseCount(JSScript *script, unsigned offset)
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{
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JS_ASSERT(offset < script->length);
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jsbytecode *pc = script->code + offset;
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if (js_CodeSpec[*pc].nuses == -1)
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return js_GetVariableStackUses(JSOp(*pc), pc);
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return js_CodeSpec[*pc].nuses;
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}
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static inline unsigned
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GetDefCount(JSScript *script, unsigned offset)
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{
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JS_ASSERT(offset < script->length);
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jsbytecode *pc = script->code + offset;
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if (js_CodeSpec[*pc].ndefs == -1)
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return js_GetEnterBlockStackDefs(NULL, script, pc);
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/*
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* Add an extra pushed value for OR/AND opcodes, so that they are included
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* in the pushed array of stack values for type inference.
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*/
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switch (JSOp(*pc)) {
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case JSOP_OR:
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case JSOP_ORX:
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case JSOP_AND:
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case JSOP_ANDX:
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return 1;
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case JSOP_FILTER:
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return 2;
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default:
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return js_CodeSpec[*pc].ndefs;
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}
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}
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/* Untrap a single PC, and retrap it at scope exit. */
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struct UntrapOpcode
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{
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jsbytecode *pc;
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bool trap;
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UntrapOpcode(JSContext *cx, JSScript *script, jsbytecode *pc)
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: pc(pc), trap(JSOp(*pc) == JSOP_TRAP)
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{
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if (trap)
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*pc = JS_GetTrapOpcode(cx, script, pc);
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}
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~UntrapOpcode()
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{
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if (trap)
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*pc = JSOP_TRAP;
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}
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};
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/*
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* Lifetime analysis. The goal of this analysis is to make a single backwards pass
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* over a script to approximate the regions where each variable is live, without
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* doing a full fixpointing live-variables pass. This is based on the algorithm
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* described in:
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*
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* "Quality and Speed in Linear-scan Register Allocation"
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* Traub et. al.
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* PLDI, 1998
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*/
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/*
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* Information about the lifetime of a local or argument. These form a linked list
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* describing successive intervals in the program where the variable's value
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* may be live. At points in the script not in one of these segments (points in
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* a 'lifetime hole'), the variable is dead and registers containing its type/payload
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* can be discarded without needing to be synced.
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*/
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struct Lifetime
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{
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/*
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* Start and end offsets of this lifetime. The variable is live at the beginning
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* of every bytecode in this (inclusive) range.
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*/
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uint32 start;
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uint32 end;
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/*
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* This is an artificial segment extending the lifetime of a variable to the
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* end of a loop, when it is live at the head of the loop. It will not be used
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* anymore in the loop body until the next iteration.
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*/
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bool loopTail;
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/* Next lifetime. The variable is dead from this->end to next->start. */
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Lifetime *next;
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Lifetime(uint32 offset, Lifetime *next)
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: start(offset), end(offset), loopTail(false), next(next)
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{}
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};
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/* Lifetime and register information for a bytecode. */
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struct LifetimeBytecode
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{
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/* If this is a loop head, offset of the loop back edge. */
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uint32 loopBackedge;
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/* Any allocation computed downstream for this bytecode. */
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mjit::RegisterAllocation *allocation;
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};
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/* Current lifetime information for a variable. */
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struct LifetimeVariable
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{
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/* If the variable is currently live, the lifetime segment. */
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Lifetime *lifetime;
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/* If the variable is currently dead, the next live segment. */
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Lifetime *saved;
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/* Jump preceding the basic block which killed this variable. */
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uint32 savedEnd;
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Lifetime * live(uint32 offset) {
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if (lifetime && lifetime->end >= offset)
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return lifetime;
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Lifetime *segment = lifetime ? lifetime : saved;
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while (segment && segment->start <= offset) {
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if (segment->end >= offset)
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return segment;
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segment = segment->next;
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}
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return NULL;
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}
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};
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/*
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* Analysis approximating variable liveness information at points in a script.
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* This is separate from analyze::Script as it is computed on every compilation
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* and thrown away afterwards.
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*/
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class LifetimeScript
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{
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analyze::Script *analysis;
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JSScript *script;
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JSFunction *fun;
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LifetimeBytecode *codeArray;
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LifetimeVariable *locals;
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LifetimeVariable *args;
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LifetimeVariable thisVar;
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LifetimeVariable **saved;
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unsigned savedCount;
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public:
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JSArenaPool pool;
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LifetimeScript();
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~LifetimeScript();
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bool analyze(JSContext *cx, analyze::Script *analysis, JSScript *script, JSFunction *fun);
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LifetimeBytecode &getCode(uint32 offset) {
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JS_ASSERT(analysis->maybeCode(offset));
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return codeArray[offset];
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}
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LifetimeBytecode &getCode(jsbytecode *pc) { return getCode(pc - script->code); }
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#ifdef DEBUG
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void dumpVariable(LifetimeVariable &var);
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void dumpLocal(unsigned i) { dumpVariable(locals[i]); }
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void dumpArg(unsigned i) { dumpVariable(args[i]); }
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#endif
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Lifetime * argLive(uint32 arg, uint32 offset) { return args[arg].live(offset); }
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Lifetime * localLive(uint32 local, uint32 offset) { return locals[local].live(offset); }
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Lifetime * thisLive(uint32 offset) { return thisVar.live(offset); }
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private:
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inline bool addVariable(JSContext *cx, LifetimeVariable &var, unsigned offset);
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inline void killVariable(JSContext *cx, LifetimeVariable &var, unsigned offset);
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inline bool extendVariable(JSContext *cx, LifetimeVariable &var, unsigned start, unsigned end);
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};
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} /* namespace analyze */
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} /* namespace js */
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#endif // jsanalyze_h___
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