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js/src/frontend/SourceNotes.h@6474c204b198 (annotated)

js/src/frontend/SourceNotes.h

Wed, 31 Dec 2014 06:09:35 +0100

author

Michael Schloh von Bennewitz <michael@schloh.com>

date

Wed, 31 Dec 2014 06:09:35 +0100

changeset 0

6474c204b198

permissions

-rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

michael@0	1	/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
michael@0	2	* vim: set ts=8 sts=4 et sw=4 tw=99:
michael@0	3	* This Source Code Form is subject to the terms of the Mozilla Public
michael@0	4	* License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0	5	* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0	6
michael@0	7	#ifndef frontend_SourceNotes_h
michael@0	8	#define frontend_SourceNotes_h
michael@0	9
michael@0	10	#include <stdint.h>
michael@0	11
michael@0	12	#include "jstypes.h"
michael@0	13
michael@0	14	typedef uint8_t jssrcnote;
michael@0	15
michael@0	16	namespace js {
michael@0	17
michael@0	18	/*
michael@0	19	* Source notes generated along with bytecode for decompiling and debugging.
michael@0	20	* A source note is a uint8_t with 5 bits of type and 3 of offset from the pc
michael@0	21	* of the previous note. If 3 bits of offset aren't enough, extended delta
michael@0	22	* notes (SRC_XDELTA) consisting of 2 set high order bits followed by 6 offset
michael@0	23	* bits are emitted before the next note. Some notes have operand offsets
michael@0	24	* encoded immediately after them, in note bytes or byte-triples.
michael@0	25	*
michael@0	26	* Source Note Extended Delta
michael@0	27	* +7-6-5-4-3+2-1-0+ +7-6-5+4-3-2-1-0+
michael@0	28	* |note-type|delta| |1 1| ext-delta |
michael@0	29	* +---------+-----+ +---+-----------+
michael@0	30	*
michael@0	31	* At most one "gettable" note (i.e., a note of type other than SRC_NEWLINE,
michael@0	32	* SRC_COLSPAN, SRC_SETLINE, and SRC_XDELTA) applies to a given bytecode.
michael@0	33	*
michael@0	34	* NB: the js_SrcNoteSpec array in BytecodeEmitter.cpp is indexed by this
michael@0	35	* enum, so its initializers need to match the order here.
michael@0	36	*
michael@0	37	* Don't forget to update XDR_BYTECODE_VERSION in vm/Xdr.h for all such
michael@0	38	* incompatible source note or other bytecode changes.
michael@0	39	*/
michael@0	40	#define FOR_EACH_SRC_NOTE_TYPE(M) \
michael@0	41	M(SRC_NULL, "null", 0) /* Terminates a note vector. */ \
michael@0	42	M(SRC_IF, "if", 0) /* JSOP_IFEQ bytecode is from an if-then. */ \
michael@0	43	M(SRC_IF_ELSE, "if-else", 1) /* JSOP_IFEQ bytecode is from an if-then-else. */ \
michael@0	44	M(SRC_COND, "cond", 1) /* JSOP_IFEQ is from conditional ?: operator. */ \
michael@0	45	M(SRC_FOR, "for", 3) /* JSOP_NOP or JSOP_POP in for(;;) loop head. */ \
michael@0	46	M(SRC_WHILE, "while", 1) /* JSOP_GOTO to for or while loop condition from before \
michael@0	47	loop, else JSOP_NOP at top of do-while loop. */ \
michael@0	48	M(SRC_FOR_IN, "for-in", 1) /* JSOP_GOTO to for-in loop condition from before \
michael@0	49	loop. */ \
michael@0	50	M(SRC_FOR_OF, "for-of", 1) /* JSOP_GOTO to for-of loop condition from before \
michael@0	51	loop. */ \
michael@0	52	M(SRC_CONTINUE, "continue", 0) /* JSOP_GOTO is a continue. */ \
michael@0	53	M(SRC_BREAK, "break", 0) /* JSOP_GOTO is a break. */ \
michael@0	54	M(SRC_BREAK2LABEL, "break2label", 0) /* JSOP_GOTO for 'break label'. */ \
michael@0	55	M(SRC_SWITCHBREAK, "switchbreak", 0) /* JSOP_GOTO is a break in a switch. */ \
michael@0	56	M(SRC_TABLESWITCH, "tableswitch", 1) /* JSOP_TABLESWITCH; offset points to end of switch. */ \
michael@0	57	M(SRC_CONDSWITCH, "condswitch", 2) /* JSOP_CONDSWITCH; 1st offset points to end of switch, \
michael@0	58	2nd points to first JSOP_CASE. */ \
michael@0	59	M(SRC_NEXTCASE, "nextcase", 1) /* Distance forward from one CASE in a CONDSWITCH to \
michael@0	60	the next. */ \
michael@0	61	M(SRC_ASSIGNOP, "assignop", 0) /* += or another assign-op follows. */ \
michael@0	62	M(SRC_TRY, "try", 1) /* JSOP_TRY, offset points to goto at the end of the \
michael@0	63	try block. */ \
michael@0	64	/* All notes below here are "gettable". See SN_IS_GETTABLE below. */ \
michael@0	65	M(SRC_COLSPAN, "colspan", 1) /* Number of columns this opcode spans. */ \
michael@0	66	M(SRC_NEWLINE, "newline", 0) /* Bytecode follows a source newline. */ \
michael@0	67	M(SRC_SETLINE, "setline", 1) /* A file-absolute source line number note. */ \
michael@0	68	M(SRC_UNUSED20, "unused20", 0) /* Unused. */ \
michael@0	69	M(SRC_UNUSED21, "unused21", 0) /* Unused. */ \
michael@0	70	M(SRC_UNUSED22, "unused22", 0) /* Unused. */ \
michael@0	71	M(SRC_UNUSED23, "unused23", 0) /* Unused. */ \
michael@0	72	M(SRC_XDELTA, "xdelta", 0) /* 24-31 are for extended delta notes. */
michael@0	73
michael@0	74	enum SrcNoteType {
michael@0	75	#define DEFINE_SRC_NOTE_TYPE(sym, name, arity) sym,
michael@0	76	FOR_EACH_SRC_NOTE_TYPE(DEFINE_SRC_NOTE_TYPE)
michael@0	77	#undef DEFINE_SRC_NOTE_TYPE
michael@0	78
michael@0	79	SRC_LAST,
michael@0	80	SRC_LAST_GETTABLE = SRC_TRY
michael@0	81	};
michael@0	82
michael@0	83	static_assert(SRC_XDELTA == 24, "SRC_XDELTA should be 24");
michael@0	84
michael@0	85	/* A source note array is terminated by an all-zero element. */
michael@0	86	inline void
michael@0	87	SN_MAKE_TERMINATOR(jssrcnote *sn)
michael@0	88	{
michael@0	89	*sn = SRC_NULL;
michael@0	90	}
michael@0	91
michael@0	92	inline bool
michael@0	93	SN_IS_TERMINATOR(jssrcnote *sn)
michael@0	94	{
michael@0	95	return *sn == SRC_NULL;
michael@0	96	}
michael@0	97
michael@0	98	} // namespace js
michael@0	99
michael@0	100	#define SN_TYPE_BITS 5
michael@0	101	#define SN_DELTA_BITS 3
michael@0	102	#define SN_XDELTA_BITS 6
michael@0	103	#define SN_TYPE_MASK (JS_BITMASK(SN_TYPE_BITS) << SN_DELTA_BITS)
michael@0	104	#define SN_DELTA_MASK ((ptrdiff_t)JS_BITMASK(SN_DELTA_BITS))
michael@0	105	#define SN_XDELTA_MASK ((ptrdiff_t)JS_BITMASK(SN_XDELTA_BITS))
michael@0	106
michael@0	107	#define SN_MAKE_NOTE(sn,t,d) (*(sn) = (jssrcnote) \
michael@0	108	(((t) << SN_DELTA_BITS) \
michael@0	109	| ((d) & SN_DELTA_MASK)))
michael@0	110	#define SN_MAKE_XDELTA(sn,d) (*(sn) = (jssrcnote) \
michael@0	111	((SRC_XDELTA << SN_DELTA_BITS) \
michael@0	112	| ((d) & SN_XDELTA_MASK)))
michael@0	113
michael@0	114	#define SN_IS_XDELTA(sn) ((*(sn) >> SN_DELTA_BITS) >= SRC_XDELTA)
michael@0	115	#define SN_TYPE(sn) ((js::SrcNoteType)(SN_IS_XDELTA(sn) \
michael@0	116	? SRC_XDELTA \
michael@0	117	: *(sn) >> SN_DELTA_BITS))
michael@0	118	#define SN_SET_TYPE(sn,type) SN_MAKE_NOTE(sn, type, SN_DELTA(sn))
michael@0	119	#define SN_IS_GETTABLE(sn) (SN_TYPE(sn) <= SRC_LAST_GETTABLE)
michael@0	120
michael@0	121	#define SN_DELTA(sn) ((ptrdiff_t)(SN_IS_XDELTA(sn) \
michael@0	122	? *(sn) & SN_XDELTA_MASK \
michael@0	123	: *(sn) & SN_DELTA_MASK))
michael@0	124	#define SN_SET_DELTA(sn,delta) (SN_IS_XDELTA(sn) \
michael@0	125	? SN_MAKE_XDELTA(sn, delta) \
michael@0	126	: SN_MAKE_NOTE(sn, SN_TYPE(sn), delta))
michael@0	127
michael@0	128	#define SN_DELTA_LIMIT ((ptrdiff_t)JS_BIT(SN_DELTA_BITS))
michael@0	129	#define SN_XDELTA_LIMIT ((ptrdiff_t)JS_BIT(SN_XDELTA_BITS))
michael@0	130
michael@0	131	/*
michael@0	132	* Offset fields follow certain notes and are frequency-encoded: an offset in
michael@0	133	* [0,0x7f] consumes one byte, an offset in [0x80,0x7fffffff] takes four, and
michael@0	134	* the high bit of the first byte is set.
michael@0	135	*/
michael@0	136	#define SN_4BYTE_OFFSET_FLAG 0x80
michael@0	137	#define SN_4BYTE_OFFSET_MASK 0x7f
michael@0	138
michael@0	139	/*
michael@0	140	* Negative SRC_COLSPAN offsets are rare, but can arise with for(;;) loops and
michael@0	141	* other constructs that generate code in non-source order. They can also arise
michael@0	142	* due to failure to update pn->pn_pos.end to be the last child's end -- such
michael@0	143	* failures are bugs to fix.
michael@0	144	*
michael@0	145	* Source note offsets in general must be non-negative and less than 0x800000,
michael@0	146	* per the above SN_4BYTE_* definitions. To encode negative colspans, we bias
michael@0	147	* them by the offset domain size and restrict non-negative colspans to less
michael@0	148	* than half this domain.
michael@0	149	*/
michael@0	150	#define SN_COLSPAN_DOMAIN ptrdiff_t(1 << 23)
michael@0	151
michael@0	152	#define SN_MAX_OFFSET ((size_t)((ptrdiff_t)SN_4BYTE_OFFSET_FLAG << 24) - 1)
michael@0	153
michael@0	154	#define SN_LENGTH(sn) ((js_SrcNoteSpec[SN_TYPE(sn)].arity == 0) ? 1 \
michael@0	155	: js_SrcNoteLength(sn))
michael@0	156	#define SN_NEXT(sn) ((sn) + SN_LENGTH(sn))
michael@0	157
michael@0	158	struct JSSrcNoteSpec {
michael@0	159	const char *name; /* name for disassembly/debugging output */
michael@0	160	int8_t arity; /* number of offset operands */
michael@0	161	};
michael@0	162
michael@0	163	extern JS_FRIEND_DATA(const JSSrcNoteSpec) js_SrcNoteSpec[];
michael@0	164	extern JS_FRIEND_API(unsigned) js_SrcNoteLength(jssrcnote *sn);
michael@0	165
michael@0	166	/*
michael@0	167	* Get and set the offset operand identified by which (0 for the first, etc.).
michael@0	168	*/
michael@0	169	extern JS_FRIEND_API(ptrdiff_t)
michael@0	170	js_GetSrcNoteOffset(jssrcnote *sn, unsigned which);
michael@0	171
michael@0	172	#endif /* frontend_SourceNotes_h */