1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/js/src/frontend/SourceNotes.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,172 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
1.5 + * vim: set ts=8 sts=4 et sw=4 tw=99:
1.6 + * This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +#ifndef frontend_SourceNotes_h
1.11 +#define frontend_SourceNotes_h
1.12 +
1.13 +#include <stdint.h>
1.14 +
1.15 +#include "jstypes.h"
1.16 +
1.17 +typedef uint8_t jssrcnote;
1.18 +
1.19 +namespace js {
1.20 +
1.21 +/*
1.22 + * Source notes generated along with bytecode for decompiling and debugging.
1.23 + * A source note is a uint8_t with 5 bits of type and 3 of offset from the pc
1.24 + * of the previous note. If 3 bits of offset aren't enough, extended delta
1.25 + * notes (SRC_XDELTA) consisting of 2 set high order bits followed by 6 offset
1.26 + * bits are emitted before the next note. Some notes have operand offsets
1.27 + * encoded immediately after them, in note bytes or byte-triples.
1.28 + *
1.29 + * Source Note Extended Delta
1.30 + * +7-6-5-4-3+2-1-0+ +7-6-5+4-3-2-1-0+
1.31 + * |note-type|delta| |1 1| ext-delta |
1.32 + * +---------+-----+ +---+-----------+
1.33 + *
1.34 + * At most one "gettable" note (i.e., a note of type other than SRC_NEWLINE,
1.35 + * SRC_COLSPAN, SRC_SETLINE, and SRC_XDELTA) applies to a given bytecode.
1.36 + *
1.37 + * NB: the js_SrcNoteSpec array in BytecodeEmitter.cpp is indexed by this
1.38 + * enum, so its initializers need to match the order here.
1.39 + *
1.40 + * Don't forget to update XDR_BYTECODE_VERSION in vm/Xdr.h for all such
1.41 + * incompatible source note or other bytecode changes.
1.42 + */
1.43 +#define FOR_EACH_SRC_NOTE_TYPE(M) \
1.44 + M(SRC_NULL, "null", 0) /* Terminates a note vector. */ \
1.45 + M(SRC_IF, "if", 0) /* JSOP_IFEQ bytecode is from an if-then. */ \
1.46 + M(SRC_IF_ELSE, "if-else", 1) /* JSOP_IFEQ bytecode is from an if-then-else. */ \
1.47 + M(SRC_COND, "cond", 1) /* JSOP_IFEQ is from conditional ?: operator. */ \
1.48 + M(SRC_FOR, "for", 3) /* JSOP_NOP or JSOP_POP in for(;;) loop head. */ \
1.49 + M(SRC_WHILE, "while", 1) /* JSOP_GOTO to for or while loop condition from before \
1.50 + loop, else JSOP_NOP at top of do-while loop. */ \
1.51 + M(SRC_FOR_IN, "for-in", 1) /* JSOP_GOTO to for-in loop condition from before \
1.52 + loop. */ \
1.53 + M(SRC_FOR_OF, "for-of", 1) /* JSOP_GOTO to for-of loop condition from before \
1.54 + loop. */ \
1.55 + M(SRC_CONTINUE, "continue", 0) /* JSOP_GOTO is a continue. */ \
1.56 + M(SRC_BREAK, "break", 0) /* JSOP_GOTO is a break. */ \
1.57 + M(SRC_BREAK2LABEL, "break2label", 0) /* JSOP_GOTO for 'break label'. */ \
1.58 + M(SRC_SWITCHBREAK, "switchbreak", 0) /* JSOP_GOTO is a break in a switch. */ \
1.59 + M(SRC_TABLESWITCH, "tableswitch", 1) /* JSOP_TABLESWITCH; offset points to end of switch. */ \
1.60 + M(SRC_CONDSWITCH, "condswitch", 2) /* JSOP_CONDSWITCH; 1st offset points to end of switch, \
1.61 + 2nd points to first JSOP_CASE. */ \
1.62 + M(SRC_NEXTCASE, "nextcase", 1) /* Distance forward from one CASE in a CONDSWITCH to \
1.63 + the next. */ \
1.64 + M(SRC_ASSIGNOP, "assignop", 0) /* += or another assign-op follows. */ \
1.65 + M(SRC_TRY, "try", 1) /* JSOP_TRY, offset points to goto at the end of the \
1.66 + try block. */ \
1.67 + /* All notes below here are "gettable". See SN_IS_GETTABLE below. */ \
1.68 + M(SRC_COLSPAN, "colspan", 1) /* Number of columns this opcode spans. */ \
1.69 + M(SRC_NEWLINE, "newline", 0) /* Bytecode follows a source newline. */ \
1.70 + M(SRC_SETLINE, "setline", 1) /* A file-absolute source line number note. */ \
1.71 + M(SRC_UNUSED20, "unused20", 0) /* Unused. */ \
1.72 + M(SRC_UNUSED21, "unused21", 0) /* Unused. */ \
1.73 + M(SRC_UNUSED22, "unused22", 0) /* Unused. */ \
1.74 + M(SRC_UNUSED23, "unused23", 0) /* Unused. */ \
1.75 + M(SRC_XDELTA, "xdelta", 0) /* 24-31 are for extended delta notes. */
1.76 +
1.77 +enum SrcNoteType {
1.78 +#define DEFINE_SRC_NOTE_TYPE(sym, name, arity) sym,
1.79 + FOR_EACH_SRC_NOTE_TYPE(DEFINE_SRC_NOTE_TYPE)
1.80 +#undef DEFINE_SRC_NOTE_TYPE
1.81 +
1.82 + SRC_LAST,
1.83 + SRC_LAST_GETTABLE = SRC_TRY
1.84 +};
1.85 +
1.86 +static_assert(SRC_XDELTA == 24, "SRC_XDELTA should be 24");
1.87 +
1.88 +/* A source note array is terminated by an all-zero element. */
1.89 +inline void
1.90 +SN_MAKE_TERMINATOR(jssrcnote *sn)
1.91 +{
1.92 + *sn = SRC_NULL;
1.93 +}
1.94 +
1.95 +inline bool
1.96 +SN_IS_TERMINATOR(jssrcnote *sn)
1.97 +{
1.98 + return *sn == SRC_NULL;
1.99 +}
1.100 +
1.101 +} // namespace js
1.102 +
1.103 +#define SN_TYPE_BITS 5
1.104 +#define SN_DELTA_BITS 3
1.105 +#define SN_XDELTA_BITS 6
1.106 +#define SN_TYPE_MASK (JS_BITMASK(SN_TYPE_BITS) << SN_DELTA_BITS)
1.107 +#define SN_DELTA_MASK ((ptrdiff_t)JS_BITMASK(SN_DELTA_BITS))
1.108 +#define SN_XDELTA_MASK ((ptrdiff_t)JS_BITMASK(SN_XDELTA_BITS))
1.109 +
1.110 +#define SN_MAKE_NOTE(sn,t,d) (*(sn) = (jssrcnote) \
1.111 + (((t) << SN_DELTA_BITS) \
1.112 + | ((d) & SN_DELTA_MASK)))
1.113 +#define SN_MAKE_XDELTA(sn,d) (*(sn) = (jssrcnote) \
1.114 + ((SRC_XDELTA << SN_DELTA_BITS) \
1.115 + | ((d) & SN_XDELTA_MASK)))
1.116 +
1.117 +#define SN_IS_XDELTA(sn) ((*(sn) >> SN_DELTA_BITS) >= SRC_XDELTA)
1.118 +#define SN_TYPE(sn) ((js::SrcNoteType)(SN_IS_XDELTA(sn) \
1.119 + ? SRC_XDELTA \
1.120 + : *(sn) >> SN_DELTA_BITS))
1.121 +#define SN_SET_TYPE(sn,type) SN_MAKE_NOTE(sn, type, SN_DELTA(sn))
1.122 +#define SN_IS_GETTABLE(sn) (SN_TYPE(sn) <= SRC_LAST_GETTABLE)
1.123 +
1.124 +#define SN_DELTA(sn) ((ptrdiff_t)(SN_IS_XDELTA(sn) \
1.125 + ? *(sn) & SN_XDELTA_MASK \
1.126 + : *(sn) & SN_DELTA_MASK))
1.127 +#define SN_SET_DELTA(sn,delta) (SN_IS_XDELTA(sn) \
1.128 + ? SN_MAKE_XDELTA(sn, delta) \
1.129 + : SN_MAKE_NOTE(sn, SN_TYPE(sn), delta))
1.130 +
1.131 +#define SN_DELTA_LIMIT ((ptrdiff_t)JS_BIT(SN_DELTA_BITS))
1.132 +#define SN_XDELTA_LIMIT ((ptrdiff_t)JS_BIT(SN_XDELTA_BITS))
1.133 +
1.134 +/*
1.135 + * Offset fields follow certain notes and are frequency-encoded: an offset in
1.136 + * [0,0x7f] consumes one byte, an offset in [0x80,0x7fffffff] takes four, and
1.137 + * the high bit of the first byte is set.
1.138 + */
1.139 +#define SN_4BYTE_OFFSET_FLAG 0x80
1.140 +#define SN_4BYTE_OFFSET_MASK 0x7f
1.141 +
1.142 +/*
1.143 + * Negative SRC_COLSPAN offsets are rare, but can arise with for(;;) loops and
1.144 + * other constructs that generate code in non-source order. They can also arise
1.145 + * due to failure to update pn->pn_pos.end to be the last child's end -- such
1.146 + * failures are bugs to fix.
1.147 + *
1.148 + * Source note offsets in general must be non-negative and less than 0x800000,
1.149 + * per the above SN_4BYTE_* definitions. To encode negative colspans, we bias
1.150 + * them by the offset domain size and restrict non-negative colspans to less
1.151 + * than half this domain.
1.152 + */
1.153 +#define SN_COLSPAN_DOMAIN ptrdiff_t(1 << 23)
1.154 +
1.155 +#define SN_MAX_OFFSET ((size_t)((ptrdiff_t)SN_4BYTE_OFFSET_FLAG << 24) - 1)
1.156 +
1.157 +#define SN_LENGTH(sn) ((js_SrcNoteSpec[SN_TYPE(sn)].arity == 0) ? 1 \
1.158 + : js_SrcNoteLength(sn))
1.159 +#define SN_NEXT(sn) ((sn) + SN_LENGTH(sn))
1.160 +
1.161 +struct JSSrcNoteSpec {
1.162 + const char *name; /* name for disassembly/debugging output */
1.163 + int8_t arity; /* number of offset operands */
1.164 +};
1.165 +
1.166 +extern JS_FRIEND_DATA(const JSSrcNoteSpec) js_SrcNoteSpec[];
1.167 +extern JS_FRIEND_API(unsigned) js_SrcNoteLength(jssrcnote *sn);
1.168 +
1.169 +/*
1.170 + * Get and set the offset operand identified by which (0 for the first, etc.).
1.171 + */
1.172 +extern JS_FRIEND_API(ptrdiff_t)
1.173 +js_GetSrcNoteOffset(jssrcnote *sn, unsigned which);
1.174 +
1.175 +#endif /* frontend_SourceNotes_h */
