js/src/frontend/BytecodeEmitter.h
author Andy Wingo <wingo@igalia.com>
Fri, 06 Dec 2013 18:27:55 +0100
changeset 174945 5f086f95b3059ed80dfe45013081478e3ed5ee82
parent 174942 d6946bd743b38c99c82eb45cf9203423cda9467c
child 174975 94cdaced90bf49679eae210824875570fb98df9c
permissions -rw-r--r--
Bug 927782 - Part 8: Record block scope ranges more precisely. r=luke

/* -*- 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 frontend_BytecodeEmitter_h
#define frontend_BytecodeEmitter_h

/*
 * JS bytecode generation.
 */

#include "jscntxt.h"
#include "jsopcode.h"
#include "jsscript.h"

#include "frontend/ParseMaps.h"
#include "frontend/SourceNotes.h"

namespace js {
namespace frontend {

class FullParseHandler;
class ObjectBox;
class ParseNode;
template <typename ParseHandler> class Parser;
class SharedContext;
class TokenStream;

class CGConstList {
    Vector<Value> list;
  public:
    CGConstList(ExclusiveContext *cx) : list(cx) {}
    bool append(Value v) { JS_ASSERT_IF(v.isString(), v.toString()->isAtom()); return list.append(v); }
    size_t length() const { return list.length(); }
    void finish(ConstArray *array);
};

struct CGObjectList {
    uint32_t            length;     /* number of emitted so far objects */
    ObjectBox           *lastbox;   /* last emitted object */

    CGObjectList() : length(0), lastbox(nullptr) {}

    unsigned add(ObjectBox *objbox);
    unsigned indexOf(JSObject *obj);
    void finish(ObjectArray *array);
    ObjectBox* find(uint32_t index);
};

struct CGTryNoteList {
    Vector<JSTryNote> list;
    CGTryNoteList(ExclusiveContext *cx) : list(cx) {}

    bool append(JSTryNoteKind kind, unsigned stackDepth, size_t start, size_t end);
    size_t length() const { return list.length(); }
    void finish(TryNoteArray *array);
};

struct CGBlockScopeList {
    Vector<BlockScopeNote> list;
    CGBlockScopeList(ExclusiveContext *cx) : list(cx) {}

    bool append(uint32_t scopeObject, uint32_t offset);
    uint32_t findEnclosingScope(uint32_t index);
    void recordEnd(uint32_t index, uint32_t offset);
    size_t length() const { return list.length(); }
    void finish(BlockScopeArray *array);
};

struct StmtInfoBCE;

// Use zero inline elements because these go on the stack and affect how many
// nested functions are possible.
typedef Vector<jsbytecode, 0> BytecodeVector;
typedef Vector<jssrcnote, 0> SrcNotesVector;

struct BytecodeEmitter
{
    typedef StmtInfoBCE StmtInfo;

    SharedContext   *const sc;      /* context shared between parsing and bytecode generation */

    BytecodeEmitter *const parent;  /* enclosing function or global context */

    Rooted<JSScript*> script;       /* the JSScript we're ultimately producing */

    struct EmitSection {
        BytecodeVector code;        /* bytecode */
        SrcNotesVector notes;       /* source notes, see below */
        ptrdiff_t   lastNoteOffset; /* code offset for last source note */
        uint32_t    currentLine;    /* line number for tree-based srcnote gen */
        uint32_t    lastColumn;     /* zero-based column index on currentLine of
                                       last SRC_COLSPAN-annotated opcode */

        EmitSection(ExclusiveContext *cx, uint32_t lineNum)
          : code(cx), notes(cx), lastNoteOffset(0), currentLine(lineNum), lastColumn(0)
        {}
    };
    EmitSection prolog, main, *current;

    /* the parser */
    Parser<FullParseHandler> *const parser;

    HandleScript    evalCaller;     /* scripted caller info for eval and dbgapi */

    StmtInfoBCE     *topStmt;       /* top of statement info stack */
    StmtInfoBCE     *topScopeStmt;  /* top lexical scope statement */
    Rooted<StaticBlockObject *> blockChain;
                                    /* compile time block scope chain */

    OwnedAtomIndexMapPtr atomIndices; /* literals indexed for mapping */
    unsigned        firstLine;      /* first line, for JSScript::initFromEmitter */

    int             stackDepth;     /* current stack depth in script frame */
    unsigned        maxStackDepth;  /* maximum stack depth so far */

    unsigned        arrayCompDepth; /* stack depth of array in comprehension */

    unsigned        emitLevel;      /* js::frontend::EmitTree recursion level */

    CGConstList     constList;      /* constants to be included with the script */

    CGObjectList    objectList;     /* list of emitted objects */
    CGObjectList    regexpList;     /* list of emitted regexp that will be
                                       cloned during execution */
    CGTryNoteList   tryNoteList;    /* list of emitted try notes */
    CGBlockScopeList blockScopeList;/* list of emitted block scope notes */

    uint16_t        typesetCount;   /* Number of JOF_TYPESET opcodes generated */

    bool            hasSingletons:1;    /* script contains singleton initializer JSOP_OBJECT */

    bool            emittingForInit:1;  /* true while emitting init expr of for; exclude 'in' */

    bool            emittingRunOnceLambda:1; /* true while emitting a lambda which is only
                                                expected to run once. */
    bool            lazyRunOnceLambda:1; /* true while lazily emitting a script for
                                          * a lambda which is only expected to run once. */

    bool isRunOnceLambda();

    bool            insideEval:1;       /* True if compiling an eval-expression or a function
                                           nested inside an eval. */

    const bool      hasGlobalScope:1;   /* frontend::CompileScript's scope chain is the
                                           global object */

    enum EmitterMode {
        Normal,

        /*
         * Emit JSOP_CALLINTRINSIC instead of JSOP_NAME and assert that
         * JSOP_NAME and JSOP_*GNAME don't ever get emitted. See the comment
         * for the field |selfHostingMode| in Parser.h for details.
         */
        SelfHosting,

        /*
         * Check the static scope chain of the root function for resolving free
         * variable accesses in the script.
         */
        LazyFunction
    };

    const EmitterMode emitterMode;

    /*
     * Note that BytecodeEmitters are magic: they own the arena "top-of-stack"
     * space above their tempMark points. This means that you cannot alloc from
     * tempLifoAlloc and save the pointer beyond the next BytecodeEmitter
     * destruction.
     */
    BytecodeEmitter(BytecodeEmitter *parent, Parser<FullParseHandler> *parser, SharedContext *sc,
                    HandleScript script, bool insideEval, HandleScript evalCaller,
                    bool hasGlobalScope, uint32_t lineNum, EmitterMode emitterMode = Normal);
    bool init();

    bool isAliasedName(ParseNode *pn);

    JS_ALWAYS_INLINE
    bool makeAtomIndex(JSAtom *atom, jsatomid *indexp) {
        AtomIndexAddPtr p = atomIndices->lookupForAdd(atom);
        if (p) {
            *indexp = p.value();
            return true;
        }

        jsatomid index = atomIndices->count();
        if (!atomIndices->add(p, atom, index))
            return false;

        *indexp = index;
        return true;
    }

    bool isInLoop();
    bool checkSingletonContext();

    bool needsImplicitThis();

    void tellDebuggerAboutCompiledScript(ExclusiveContext *cx);

    inline TokenStream *tokenStream();

    BytecodeVector &code() const { return current->code; }
    jsbytecode *code(ptrdiff_t offset) const { return current->code.begin() + offset; }
    ptrdiff_t offset() const { return current->code.end() - current->code.begin(); }
    ptrdiff_t prologOffset() const { return prolog.code.end() - prolog.code.begin(); }
    void switchToMain() { current = &main; }
    void switchToProlog() { current = &prolog; }

    SrcNotesVector &notes() const { return current->notes; }
    ptrdiff_t lastNoteOffset() const { return current->lastNoteOffset; }
    unsigned currentLine() const { return current->currentLine; }
    unsigned lastColumn() const { return current->lastColumn; }

    inline ptrdiff_t countFinalSourceNotes();

    bool reportError(ParseNode *pn, unsigned errorNumber, ...);
    bool reportStrictWarning(ParseNode *pn, unsigned errorNumber, ...);
    bool reportStrictModeError(ParseNode *pn, unsigned errorNumber, ...);
};

/*
 * Emit one bytecode.
 */
ptrdiff_t
Emit1(ExclusiveContext *cx, BytecodeEmitter *bce, JSOp op);

/*
 * Emit two bytecodes, an opcode (op) with a byte of immediate operand (op1).
 */
ptrdiff_t
Emit2(ExclusiveContext *cx, BytecodeEmitter *bce, JSOp op, jsbytecode op1);

/*
 * Emit three bytecodes, an opcode with two bytes of immediate operands.
 */
ptrdiff_t
Emit3(ExclusiveContext *cx, BytecodeEmitter *bce, JSOp op, jsbytecode op1, jsbytecode op2);

/*
 * Emit (1 + extra) bytecodes, for N bytes of op and its immediate operand.
 */
ptrdiff_t
EmitN(ExclusiveContext *cx, BytecodeEmitter *bce, JSOp op, size_t extra);

/*
 * Emit code into bce for the tree rooted at pn.
 */
bool
EmitTree(ExclusiveContext *cx, BytecodeEmitter *bce, ParseNode *pn);

/*
 * Emit function code using bce for the tree rooted at body.
 */
bool
EmitFunctionScript(ExclusiveContext *cx, BytecodeEmitter *bce, ParseNode *body);

/*
 * Append a new source note of the given type (and therefore size) to bce's
 * notes dynamic array, updating bce->noteCount. Return the new note's index
 * within the array pointed at by bce->current->notes. Return -1 if out of
 * memory.
 */
int
NewSrcNote(ExclusiveContext *cx, BytecodeEmitter *bce, SrcNoteType type);

int
NewSrcNote2(ExclusiveContext *cx, BytecodeEmitter *bce, SrcNoteType type, ptrdiff_t offset);

int
NewSrcNote3(ExclusiveContext *cx, BytecodeEmitter *bce, SrcNoteType type, ptrdiff_t offset1,
               ptrdiff_t offset2);

/* NB: this function can add at most one extra extended delta note. */
bool
AddToSrcNoteDelta(ExclusiveContext *cx, BytecodeEmitter *bce, jssrcnote *sn, ptrdiff_t delta);

bool
FinishTakingSrcNotes(ExclusiveContext *cx, BytecodeEmitter *bce, jssrcnote *notes);

/*
 * Finish taking source notes in cx's notePool, copying final notes to the new
 * stable store allocated by the caller and passed in via notes. Return false
 * on malloc failure, which means this function reported an error.
 *
 * Use this to compute the number of jssrcnotes to allocate and pass in via
 * notes. This method knows a lot about details of FinishTakingSrcNotes, so
 * DON'T CHANGE js::frontend::FinishTakingSrcNotes WITHOUT CHECKING WHETHER
 * THIS METHOD NEEDS CORRESPONDING CHANGES!
 */
inline ptrdiff_t
BytecodeEmitter::countFinalSourceNotes()
{
    ptrdiff_t diff = prologOffset() - prolog.lastNoteOffset;
    ptrdiff_t cnt = prolog.notes.length() + main.notes.length() + 1;
    if (prolog.notes.length() && prolog.currentLine != firstLine) {
        if (diff > SN_DELTA_MASK)
            cnt += JS_HOWMANY(diff - SN_DELTA_MASK, SN_XDELTA_MASK);
        cnt += 2 + ((firstLine > SN_3BYTE_OFFSET_MASK) << 1);
    } else if (diff > 0) {
        if (main.notes.length()) {
            jssrcnote *sn = main.notes.begin();
            diff -= SN_IS_XDELTA(sn)
                    ? SN_XDELTA_MASK - (*sn & SN_XDELTA_MASK)
                    : SN_DELTA_MASK - (*sn & SN_DELTA_MASK);
        }
        if (diff > 0)
            cnt += JS_HOWMANY(diff, SN_XDELTA_MASK);
    }
    return cnt;
}

} /* namespace frontend */
} /* namespace js */

#endif /* frontend_BytecodeEmitter_h */