jsemit.h

java script test programing source code

 * A source note is a uint8 with 5 bits of type and 3 of offset from the pc of
 * the previous note.  If 3 bits of offset aren't enough, extended delta notes
 * (SRC_XDELTA) consisting of 2 set high order bits followed by 6 offset bits
 * are emitted before the next note.  Some notes have operand offsets encoded
 * immediately after them, in note bytes or byte-triples.
 *
 *                 Source Note               Extended Delta
 *              +7-6-5-4-3+2-1-0+           +7-6-5+4-3-2-1-0+
 *              |note-type|delta|           |1 1| ext-delta |
 *              +---------+-----+           +---+-----------+
 *
 * At most one "gettable" note (i.e., a note of type other than SRC_NEWLINE,
 * SRC_SETLINE, and SRC_XDELTA) applies to a given bytecode.
 *
 * NB: the js_SrcNoteSpec array in jsemit.c is indexed by this enum, so its
 * initializers need to match the order here.
 *
 * Note on adding new source notes: every pair of bytecodes (A, B) where A and
 * B have disjoint sets of source notes that could apply to each bytecode may
 * reuse the same note type value for two notes (snA, snB) that have the same
 * arity, offsetBias, and isSpanDep initializers in js_SrcNoteSpec.  This is
 * why SRC_IF and SRC_INITPROP have the same value below.  For bad historical
 * reasons, some bytecodes below that could be overlayed have not been, but
 * before using SRC_EXTENDED, consider compressing the existing note types.
 *
 * Don't forget to update JSXDR_BYTECODE_VERSION in jsxdrapi.h for all such
 * incompatible source note or other bytecode changes.
 */
typedef enum JSSrcNoteType {
    SRC_NULL        = 0,        /* terminates a note vector */
    SRC_IF          = 1,        /* JSOP_IFEQ bytecode is from an if-then */
    SRC_INITPROP    = 1,        /* disjoint meaning applied to JSOP_INITELEM or
                                   to an index label in a regular (structuring)
                                   or a destructuring object initialiser */
    SRC_IF_ELSE     = 2,        /* JSOP_IFEQ bytecode is from an if-then-else */
    SRC_WHILE       = 3,        /* JSOP_IFEQ is from a while loop */
    SRC_FOR         = 4,        /* JSOP_NOP or JSOP_POP in for loop head */
    SRC_CONTINUE    = 5,        /* JSOP_GOTO is a continue, not a break;
                                   also used on JSOP_ENDINIT if extra comma
                                   at end of array literal: [1,2,,] */
    SRC_DECL        = 6,        /* type of a declaration (var, const, let*) */
    SRC_DESTRUCT    = 6,        /* JSOP_DUP starting a destructuring assignment
                                   operation, with SRC_DECL_* offset operand */
    SRC_PCDELTA     = 7,        /* distance forward from comma-operator to
                                   next POP, or from CONDSWITCH to first CASE
                                   opcode, etc. -- always a forward delta */
    SRC_GROUPASSIGN = 7,        /* SRC_DESTRUCT variant for [a, b] = [c, d] */
    SRC_ASSIGNOP    = 8,        /* += or another assign-op follows */
    SRC_COND        = 9,        /* JSOP_IFEQ is from conditional ?: operator */
    SRC_BRACE       = 10,       /* mandatory brace, for scope or to avoid
                                   dangling else */
    SRC_HIDDEN      = 11,       /* opcode shouldn't be decompiled */
    SRC_PCBASE      = 12,       /* distance back from annotated getprop or
                                   setprop op to left-most obj.prop.subprop
                                   bytecode -- always a backward delta */
    SRC_METHODBASE  = 13,       /* SRC_PCBASE variant for obj.function::foo
                                   gets and sets; disjoint from SRC_LABEL by
                                   bytecode to which it applies */
    SRC_LABEL       = 13,       /* JSOP_NOP for label: with atomid immediate */
    SRC_LABELBRACE  = 14,       /* JSOP_NOP for label: {...} begin brace */
    SRC_ENDBRACE    = 15,       /* JSOP_NOP for label: {...} end brace */
    SRC_BREAK2LABEL = 16,       /* JSOP_GOTO for 'break label' with atomid */
    SRC_CONT2LABEL  = 17,       /* JSOP_GOTO for 'continue label' with atomid */
    SRC_SWITCH      = 18,       /* JSOP_*SWITCH with offset to end of switch,
                                   2nd off to first JSOP_CASE if condswitch */
    SRC_FUNCDEF     = 19,       /* JSOP_NOP for function f() with atomid */
    SRC_CATCH       = 20,       /* catch block has guard */
    SRC_EXTENDED    = 21,       /* extended source note, 32-159, in next byte */
    SRC_NEWLINE     = 22,       /* bytecode follows a source newline */
    SRC_SETLINE     = 23,       /* a file-absolute source line number note */
    SRC_XDELTA      = 24        /* 24-31 are for extended delta notes */
} JSSrcNoteType;

/*
 * Constants for the SRC_DECL source note.  Note that span-dependent bytecode
 * selection means that any SRC_DECL offset greater than SRC_DECL_LET may need
 * to be adjusted, but these "offsets" are too small to span a span-dependent
 * instruction, so can be used to denote distinct declaration syntaxes to the
 * decompiler.
 *
 * NB: the var_prefix array in jsopcode.c depends on these dense indexes from
 * SRC_DECL_VAR through SRC_DECL_LET.
 */
#define SRC_DECL_VAR            0
#define SRC_DECL_CONST          1
#define SRC_DECL_LET            2
#define SRC_DECL_NONE           3

#define SN_TYPE_BITS            5
#define SN_DELTA_BITS           3
#define SN_XDELTA_BITS          6
#define SN_TYPE_MASK            (JS_BITMASK(SN_TYPE_BITS) << SN_DELTA_BITS)
#define SN_DELTA_MASK           ((ptrdiff_t)JS_BITMASK(SN_DELTA_BITS))
#define SN_XDELTA_MASK          ((ptrdiff_t)JS_BITMASK(SN_XDELTA_BITS))

#define SN_MAKE_NOTE(sn,t,d)    (*(sn) = (jssrcnote)                          \
                                          (((t) << SN_DELTA_BITS)             \
                                           | ((d) & SN_DELTA_MASK)))
#define SN_MAKE_XDELTA(sn,d)    (*(sn) = (jssrcnote)                          \
                                          ((SRC_XDELTA << SN_DELTA_BITS)      \
                                           | ((d) & SN_XDELTA_MASK)))

#define SN_IS_XDELTA(sn)        ((*(sn) >> SN_DELTA_BITS) >= SRC_XDELTA)
#define SN_TYPE(sn)             (SN_IS_XDELTA(sn) ? SRC_XDELTA                \
                                                  : *(sn) >> SN_DELTA_BITS)
#define SN_SET_TYPE(sn,type)    SN_MAKE_NOTE(sn, type, SN_DELTA(sn))
#define SN_IS_GETTABLE(sn)      (SN_TYPE(sn) < SRC_NEWLINE)

#define SN_DELTA(sn)            ((ptrdiff_t)(SN_IS_XDELTA(sn)                 \
                                             ? *(sn) & SN_XDELTA_MASK         \
                                             : *(sn) & SN_DELTA_MASK))
#define SN_SET_DELTA(sn,delta)  (SN_IS_XDELTA(sn)                             \
                                 ? SN_MAKE_XDELTA(sn, delta)                  \
                                 : SN_MAKE_NOTE(sn, SN_TYPE(sn), delta))

#define SN_DELTA_LIMIT          ((ptrdiff_t)JS_BIT(SN_DELTA_BITS))
#define SN_XDELTA_LIMIT         ((ptrdiff_t)JS_BIT(SN_XDELTA_BITS))

/*
 * Offset fields follow certain notes and are frequency-encoded: an offset in
 * [0,0x7f] consumes one byte, an offset in [0x80,0x7fffff] takes three, and
 * the high bit of the first byte is set.
 */
#define SN_3BYTE_OFFSET_FLAG    0x80
#define SN_3BYTE_OFFSET_MASK    0x7f

typedef struct JSSrcNoteSpec {
    const char      *name;      /* name for disassembly/debugging output */
    uint8           arity;      /* number of offset operands */
    uint8           offsetBias; /* bias of offset(s) from annotated pc */
    int8            isSpanDep;  /* 1 or -1 if offsets could span extended ops,
                                   0 otherwise; sign tells span direction */
} JSSrcNoteSpec;

extern JS_FRIEND_DATA(JSSrcNoteSpec) js_SrcNoteSpec[];
extern JS_FRIEND_API(uintN)          js_SrcNoteLength(jssrcnote *sn);

#define SN_LENGTH(sn)           ((js_SrcNoteSpec[SN_TYPE(sn)].arity == 0) ? 1 \
                                 : js_SrcNoteLength(sn))
#define SN_NEXT(sn)             ((sn) + SN_LENGTH(sn))

/* A source note array is terminated by an all-zero element. */
#define SN_MAKE_TERMINATOR(sn)  (*(sn) = SRC_NULL)
#define SN_IS_TERMINATOR(sn)    (*(sn) == SRC_NULL)

/*
 * Append a new source note of the given type (and therefore size) to cg's
 * notes dynamic array, updating cg->noteCount.  Return the new note's index
 * within the array pointed at by cg->current->notes.  Return -1 if out of
 * memory.
 */
extern intN
js_NewSrcNote(JSContext *cx, JSCodeGenerator *cg, JSSrcNoteType type);

extern intN
js_NewSrcNote2(JSContext *cx, JSCodeGenerator *cg, JSSrcNoteType type,
               ptrdiff_t offset);

extern intN
js_NewSrcNote3(JSContext *cx, JSCodeGenerator *cg, JSSrcNoteType type,
               ptrdiff_t offset1, ptrdiff_t offset2);

/*
 * NB: this function can add at most one extra extended delta note.
 */
extern jssrcnote *
js_AddToSrcNoteDelta(JSContext *cx, JSCodeGenerator *cg, jssrcnote *sn,
                     ptrdiff_t delta);

/*
 * Get and set the offset operand identified by which (0 for the first, etc.).
 */
extern JS_FRIEND_API(ptrdiff_t)
js_GetSrcNoteOffset(jssrcnote *sn, uintN which);

extern JSBool
js_SetSrcNoteOffset(JSContext *cx, JSCodeGenerator *cg, uintN index,
                    uintN which, ptrdiff_t offset);

/*
 * 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.
 *
 * To compute the number of jssrcnotes to allocate and pass in via notes, use
 * the CG_COUNT_FINAL_SRCNOTES macro.  This macro knows a lot about details of
 * js_FinishTakingSrcNotes, SO DON'T CHANGE jsemit.c's js_FinishTakingSrcNotes
 * FUNCTION WITHOUT CHECKING WHETHER THIS MACRO NEEDS CORRESPONDING CHANGES!
 */
#define CG_COUNT_FINAL_SRCNOTES(cg, cnt)                                      \
    JS_BEGIN_MACRO                                                            \
        ptrdiff_t diff_ = CG_PROLOG_OFFSET(cg) - (cg)->prolog.lastNoteOffset; \
        cnt = (cg)->prolog.noteCount + (cg)->main.noteCount + 1;              \
        if ((cg)->prolog.noteCount &&                                         \
            (cg)->prolog.currentLine != (cg)->firstLine) {                    \
            if (diff_ > SN_DELTA_MASK)                                        \
                cnt += JS_HOWMANY(diff_ - SN_DELTA_MASK, SN_XDELTA_MASK);     \
            cnt += 2 + (((cg)->firstLine > SN_3BYTE_OFFSET_MASK) << 1);       \
        } else if (diff_ > 0) {                                               \
            if (cg->main.noteCount) {                                         \
                jssrcnote *sn_ = (cg)->main.notes;                            \
                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);                     \
        }                                                                     \
    JS_END_MACRO

extern JSBool
js_FinishTakingSrcNotes(JSContext *cx, JSCodeGenerator *cg, jssrcnote *notes);

/*
 * Allocate cg->treeContext.tryCount notes (plus one for the end sentinel)
 * from cx->tempPool and set up cg->tryBase/tryNext for exactly tryCount
 * js_NewTryNote calls.  The storage is freed by js_FinishCodeGenerator.
 */
extern JSBool
js_AllocTryNotes(JSContext *cx, JSCodeGenerator *cg);

/*
 * Grab the next trynote slot in cg, filling it in appropriately.
 */
extern JSTryNote *
js_NewTryNote(JSContext *cx, JSCodeGenerator *cg, ptrdiff_t start,
              ptrdiff_t end, ptrdiff_t catchStart);

/*
 * Finish generating exception information into the space at notes.  As with
 * js_FinishTakingSrcNotes, the caller must use CG_COUNT_FINAL_TRYNOTES(cg) to
 * preallocate enough space in a JSTryNote[] to pass as the notes parameter of
 * js_FinishTakingTryNotes.
 */
#define CG_COUNT_FINAL_TRYNOTES(cg, cnt)                                      \
    JS_BEGIN_MACRO                                                            \
        cnt = ((cg)->tryNext > (cg)->tryBase)                                 \
              ? PTRDIFF(cg->tryNext, cg->tryBase, JSTryNote) + 1              \
              : 0;                                                            \
    JS_END_MACRO

extern void
js_FinishTakingTryNotes(JSContext *cx, JSCodeGenerator *cg, JSTryNote *notes);

JS_END_EXTERN_C

#endif /* jsemit_h___ */