gecko/js/src/jsanalyze.h

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 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
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 * 1.1 (the "License"); you may not use this file except in compliance with
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 *
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 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is the Mozilla SpiderMonkey bytecode analysis
 *
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 *
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 * ***** END LICENSE BLOCK ***** */

/* Definitions for javascript analysis. */

#ifndef jsanalyze_h___
#define jsanalyze_h___

#include "jsarena.h"
#include "jscntxt.h"
#include "jsinfer.h"
#include "jsscript.h"

struct JSScript;

namespace js {
namespace analyze {

class Script;

/* Information about a bytecode instruction. */
struct Bytecode
{
    friend class Script;

    /* Whether there are any incoming jumps to this instruction. */
    bool jumpTarget : 1;

    /* Whether this instruction has been analyzed to get its output defines and stack. */
    bool analyzed : 1;

    /* Whether this is a catch/finally entry point. */
    bool exceptionEntry : 1;

    /* Whether this is in a try block. */
    bool inTryBlock : 1;

    /* Whether this is a method JIT safe point. */
    bool safePoint : 1;

    /* Stack depth before this opcode. */
    uint32 stackDepth;

    /*
     * The set of locals defined at this point.  This does not include locals which
     * were unconditionally defined at an earlier point in the script.
     */
    uint32 defineCount;
    uint32 *defineArray;

    Bytecode(Script *script, unsigned offset)
    {
        PodZero(this);

#ifdef JS_TYPE_INFERENCE
        this->script = script;
        this->offset = offset;
#endif
    }

  private:
    bool mergeDefines(JSContext *cx, Script *script, bool initial,
                      uint32 newDepth, types::TypeStack *newStack,
                      uint32 *newArray, uint32 newCount);

    /* Whether a local variable is in the define set at this bytecode. */
    bool isDefined(uint32 slot)
    {
        JS_ASSERT(analyzed);
        for (unsigned ind = 0; ind < defineCount; ind++) {
            if (defineArray[ind] == slot)
                return true;
        }
        return false;
    }

#ifdef JS_TYPE_INFERENCE
  public:

    Script *script;
    unsigned offset;

    /* Contents of the stack when this instruction is executed. */
    types::TypeStack *inStack;

    /* Array of stack nodes pushed by this instruction. */
    types::TypeStack *pushedArray;

    /* Any new object created at this bytecode. */
    types::TypeObject *initObject;

    /* Whether this bytecode needs to have its effects monitored dynamically. */
    bool monitorNeeded;

    /*
     * For logging, whether we've generated warnings due to a mismatch between the
     * actual and inferred types at this bytecode.
     */
    bool missingTypes;

    /* Pool which constraints on this instruction should use. */
    inline JSArenaPool &pool();

    /* Get the type set for the Nth value popped by this instruction. */
    inline types::TypeSet *popped(unsigned num);

    /* Get the type set for the Nth value pushed by this instruction. */
    inline types::TypeSet *pushed(unsigned num);

    /* Mark a trivially determined fixed type for a value pushed by this instruction. */
    inline void setFixed(JSContext *cx, unsigned num, types::jstype type);

    /*
     * Get the new object at this bytecode. propagation will be performed from
     * either Object or Array, per isArray.
     */
    inline types::TypeObject* getInitObject(JSContext *cx, bool isArray);

    /*
     * Get the type tag which values in this set must have, or JSVAL_TYPE_UNKNOWN
     * if the type tag is not known.
     */
    inline JSValueType getKnownTypeTag();

    void print(JSContext *cx, FILE *out);

#endif /* JS_TYPE_INFERENCE */

};

/* Information about a script. */
class Script
{
    friend struct Bytecode;

    JSScript *script;
    Bytecode **codeArray;

    /* Maximum number of locals to consider for a script. */
    static const unsigned LOCAL_LIMIT = 50;

    /* Offsets at which each local becomes unconditionally defined, or a value below. */
    uint32 *locals;

    static const uint32 LOCAL_USE_BEFORE_DEF = uint32(-1);
    static const uint32 LOCAL_CONDITIONALLY_DEFINED = uint32(-2);

    bool outOfMemory;
    bool hadFailure;
    bool usesRval;
    bool usesScope;

  public:
    /* Pool for allocating analysis structures which will not outlive this script. */
    JSArenaPool pool;

    void init(JSScript *script);
    void analyze(JSContext *cx);
    void destroy();

    /*
     * For analysis scripts allocated on the stack.  Scripts don't have constructors,
     * and must be zeroed out before being used.
     */
    ~Script() { destroy(); }

    /* Whether we ran out of memory during analysis. */
    bool OOM() { return outOfMemory; }

    /* Whether the script was analyzed successfully. */
    bool failed() { return hadFailure; }

    /* Whether there are POPV/SETRVAL bytecodes which can write to the frame's rval. */
    bool usesReturnValue() const { return usesRval; }

    /* Whether there are NAME bytecodes which can access the frame's scope chain. */
    bool usesScopeChain() const { return usesScope; }

    /* Whether the script has been analyzed. */
    bool hasAnalyzed() const { return !!codeArray; }

    /* Script being analyzed. */
    JSScript *getScript() const { return script; }

    /* Accessors for bytecode information. */

    Bytecode& getCode(uint32 offset) {
        JS_ASSERT(offset < script->length);
        JS_ASSERT(codeArray[offset]);
        return *codeArray[offset];
    }
    Bytecode& getCode(const jsbytecode *pc) { return getCode(pc - script->code); }

    Bytecode* maybeCode(uint32 offset) {
        JS_ASSERT(offset < script->length);
        return codeArray[offset];
    }
    Bytecode* maybeCode(const jsbytecode *pc) { return maybeCode(pc - script->code); }

    bool jumpTarget(uint32 offset) {
        JS_ASSERT(offset < script->length);
        return codeArray[offset] && codeArray[offset]->jumpTarget;
    }
    bool jumpTarget(const jsbytecode *pc) { return jumpTarget(pc - script->code); }

    /* Accessors for local variable information. */

    unsigned localCount() {
        return (script->nfixed >= LOCAL_LIMIT) ? LOCAL_LIMIT : script->nfixed;
    }

    bool localHasUseBeforeDef(uint32 local) {
        JS_ASSERT(!failed());
        return local >= localCount() || locals[local] == LOCAL_USE_BEFORE_DEF;
    }

    /* These return true for variables that may have a use before def. */
    bool localDefined(uint32 local, uint32 offset) {
        return localHasUseBeforeDef(local) || (locals[local] <= offset) ||
            getCode(offset).isDefined(local);
    }
    bool localDefined(uint32 local, jsbytecode *pc) {
        return localDefined(local, pc - script->code);
    }

  private:
    void setOOM(JSContext *cx) {
        if (!outOfMemory)
            js_ReportOutOfMemory(cx);
        outOfMemory = true;
        hadFailure = true;
    }

    inline bool addJump(JSContext *cx, unsigned offset,
                        unsigned *currentOffset, unsigned *forwardJump,
                        unsigned stackDepth, types::TypeStack *stack,
                        uint32 *defineArray, unsigned defineCount);

    inline void setLocal(uint32 local, uint32 offset);

#ifdef JS_TYPE_INFERENCE
  public:

    /* Unique identifier within the compartment. */
    unsigned id;

    /* Function this script is the body for, if there is one. */
    types::TypeFunction *function;

    /* Argument count and name from the function. */
    unsigned argCount;
    jsid thisName;

    /* List of objects associated with this script. */
    types::TypeObject *objects;

    /*
     * Location where the definition of this script occurs, representing any
     * nesting for scope lookups.  NULL for global scripts.
     */
    JSScript *parent;
    const jsbytecode *parentpc;

    /*
     * Variables defined by this script.  This includes local variables defined
     * with 'var' or 'let', formal arguments, unnamed arguments, and properties
     * of the script itself (*not* properties of the script's prototype).
     */
    types::VariableSet localTypes;

    /* Types of the 'this' variable in this script. */
    types::TypeSet thisTypes;

    /* Array of local variable names, computed by js_GetLocalNameArray. */
    jsuword *localNames;

    void setFunction(JSContext *cx, JSFunction *fun);

    inline bool isEval() { return parent && !function; }

    /*
     * Get the non-eval script which this one is nested in, returning this script
     * if it was not produced as the result of an eval.
     */
    inline Script *evalParent();

    /* Bytecode where this script is nested. */
    inline Bytecode *parentCode();

    void print(JSContext *cx);

    /* Helpers */

    /* Temporary state for handling opcodes with fused behavior. */
    struct TypeState {
        /* Last opcode was JSOP_GETTER or JSOP_SETTER. */
        bool hasGetSet;

        TypeState()
            : hasGetSet(false)
        {}
    };

    /* Analyzes a bytecode, generating type constraints describing its behavior. */
    void analyzeTypes(JSContext *cx, Bytecode *codeType, TypeState &state);

    /*
     * Get the name to use for the local with specified index.  Stack indicates the
     * point of the access, for looking up let variables.
     */
    inline jsid getLocalId(unsigned index, types::TypeStack *stack);

    /* Get the name to use for the argument with the specified index. */
    inline jsid getArgumentId(unsigned index);

    /* Get the type set to use for a stack slot at a fixed stack depth. */
    inline types::TypeSet *getStackTypes(unsigned index, types::TypeStack *stack);

#endif /* JS_TYPE_INFERENCE */

};

static inline unsigned
GetBytecodeLength(jsbytecode *pc)
{
    JSOp op = (JSOp)*pc;
    JS_ASSERT(op < JSOP_LIMIT);
    JS_ASSERT(op != JSOP_TRAP);

    if (js_CodeSpec[op].length != -1)
        return js_CodeSpec[op].length;
    return js_GetVariableBytecodeLength(pc);
}

static inline unsigned
GetUseCount(JSScript *script, unsigned offset)
{
    JS_ASSERT(offset < script->length);
    jsbytecode *pc = script->code + offset;
    if (js_CodeSpec[*pc].nuses == -1)
        return js_GetVariableStackUses(JSOp(*pc), pc);
    return js_CodeSpec[*pc].nuses;
}

static inline unsigned
GetDefCount(JSScript *script, unsigned offset)
{
    JS_ASSERT(offset < script->length);
    jsbytecode *pc = script->code + offset;
    if (js_CodeSpec[*pc].ndefs == -1)
        return js_GetEnterBlockStackDefs(NULL, script, pc);

    /*
     * 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_ORX:
      case JSOP_AND:
      case JSOP_ANDX:
        return 1;
      default:
        return js_CodeSpec[*pc].ndefs;
    }
}

} /* namespace analyze */
} /* namespace js */

#endif // jsanalyze_h___