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/* -*- 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_SourceNotes_h
#define frontend_SourceNotes_h
#include <stdint.h>
#include "jstypes.h"
typedef uint8_t jssrcnote;
namespace js {
/*
* Source notes generated along with bytecode for decompiling and debugging.
* A source note is a uint8_t 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_COLSPAN, SRC_SETLINE, and SRC_XDELTA) applies to a given bytecode.
*
* NB: the js_SrcNoteSpec array in BytecodeEmitter.cpp is indexed by this
* enum, so its initializers need to match the order here.
*/
#define FOR_EACH_SRC_NOTE_TYPE(M) \
M(SRC_NULL, "null", 0) /* Terminates a note vector. */ \
M(SRC_IF, "if", 0) /* JSOP_IFEQ bytecode is from an if-then. */ \
M(SRC_IF_ELSE, "if-else", 1) /* JSOP_IFEQ bytecode is from an if-then-else. */ \
M(SRC_COND, "cond", 1) /* JSOP_IFEQ is from conditional ?: operator. */ \
M(SRC_FOR, "for", 3) /* JSOP_NOP or JSOP_POP in for(;;) loop head. */ \
M(SRC_WHILE, "while", 1) /* JSOP_GOTO to for or while loop condition from before \
loop, else JSOP_NOP at top of do-while loop. */ \
M(SRC_FOR_IN, "for-in", 1) /* JSOP_GOTO to for-in loop condition from before \
loop. */ \
M(SRC_FOR_OF, "for-of", 1) /* JSOP_GOTO to for-of loop condition from before \
loop. */ \
M(SRC_CONTINUE, "continue", 0) /* JSOP_GOTO is a continue. */ \
M(SRC_BREAK, "break", 0) /* JSOP_GOTO is a break. */ \
M(SRC_BREAK2LABEL, "break2label", 0) /* JSOP_GOTO for 'break label'. */ \
M(SRC_SWITCHBREAK, "switchbreak", 0) /* JSOP_GOTO is a break in a switch. */ \
M(SRC_TABLESWITCH, "tableswitch", 1) /* JSOP_TABLESWITCH; offset points to end of switch. */ \
M(SRC_CONDSWITCH, "condswitch", 2) /* JSOP_CONDSWITCH; 1st offset points to end of switch, \
2nd points to first JSOP_CASE. */ \
M(SRC_NEXTCASE, "nextcase", 1) /* Distance forward from one CASE in a CONDSWITCH to \
the next. */ \
M(SRC_ASSIGNOP, "assignop", 0) /* += or another assign-op follows. */ \
M(SRC_CLASS_SPAN, "class", 2) /* The starting and ending offsets for the class, used \
for toString correctness for default ctors. */ \
M(SRC_TRY, "try", 1) /* JSOP_TRY, offset points to goto at the end of the \
try block. */ \
/* All notes above here are "gettable". See SN_IS_GETTABLE below. */ \
M(SRC_COLSPAN, "colspan", 1) /* Number of columns this opcode spans. */ \
M(SRC_NEWLINE, "newline", 0) /* Bytecode follows a source newline. */ \
M(SRC_SETLINE, "setline", 1) /* A file-absolute source line number note. */ \
M(SRC_UNUSED21, "unused21", 0) /* Unused. */ \
M(SRC_UNUSED22, "unused22", 0) /* Unused. */ \
M(SRC_UNUSED23, "unused23", 0) /* Unused. */ \
M(SRC_XDELTA, "xdelta", 0) /* 24-31 are for extended delta notes. */
enum SrcNoteType {
#define DEFINE_SRC_NOTE_TYPE(sym, name, arity) sym,
FOR_EACH_SRC_NOTE_TYPE(DEFINE_SRC_NOTE_TYPE)
#undef DEFINE_SRC_NOTE_TYPE
SRC_LAST,
SRC_LAST_GETTABLE = SRC_TRY
};
static_assert(SRC_XDELTA == 24, "SRC_XDELTA should be 24");
/* A source note array is terminated by an all-zero element. */
inline void
SN_MAKE_TERMINATOR(jssrcnote* sn)
{
*sn = SRC_NULL;
}
inline bool
SN_IS_TERMINATOR(jssrcnote* sn)
{
return *sn == SRC_NULL;
}
} // namespace js
#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) ((js::SrcNoteType)(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_LAST_GETTABLE)
#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 [0x80,0x7fffffff] takes four, and
* the high bit of the first byte is set.
*/
#define SN_4BYTE_OFFSET_FLAG 0x80
#define SN_4BYTE_OFFSET_MASK 0x7f
#define SN_OFFSET_BITS 31
#define SN_MAX_OFFSET (((size_t) 1 << SN_OFFSET_BITS) - 1)
inline bool
SN_REPRESENTABLE_OFFSET(ptrdiff_t offset)
{
return 0 <= offset && size_t(offset) <= SN_MAX_OFFSET;
}
/*
* SRC_COLSPAN values represent changes to the column number. Colspans are
* signed: negative changes arise in describing constructs like for(;;) loops,
* that generate code in non-source order. (Negative colspans also have a
* history of indicating bugs in updating ParseNodes' source locations.)
*
* We store colspans using the same variable-length encoding as offsets,
* described above. However, unlike offsets, colspans are signed, so we truncate
* colspans (SN_COLSPAN_TO_OFFSET) for storage as offsets, and sign-extend
* offsets into colspans when we read them (SN_OFFSET_TO_COLSPAN).
*/
#define SN_COLSPAN_SIGN_BIT (1 << (SN_OFFSET_BITS - 1))
#define SN_MIN_COLSPAN (-SN_COLSPAN_SIGN_BIT)
#define SN_MAX_COLSPAN (SN_COLSPAN_SIGN_BIT - 1)
inline bool
SN_REPRESENTABLE_COLSPAN(ptrdiff_t colspan)
{
return SN_MIN_COLSPAN <= colspan && colspan <= SN_MAX_COLSPAN;
}
inline ptrdiff_t
SN_OFFSET_TO_COLSPAN(ptrdiff_t offset) {
// There should be no bits set outside the field we're going to sign-extend.
MOZ_ASSERT(!(offset & ~((1U << SN_OFFSET_BITS) - 1)));
// Sign-extend the least significant SN_OFFSET_BITS bits.
return (offset ^ SN_COLSPAN_SIGN_BIT) - SN_COLSPAN_SIGN_BIT;
}
inline ptrdiff_t
SN_COLSPAN_TO_OFFSET(ptrdiff_t colspan) {
// Truncate the two's complement colspan, for storage as an offset.
ptrdiff_t offset = colspan & ((1U << SN_OFFSET_BITS) - 1);
// When we read this back, we'd better get the value we stored.
MOZ_ASSERT(SN_OFFSET_TO_COLSPAN(offset) == colspan);
return offset;
}
#define SN_LENGTH(sn) ((js_SrcNoteSpec[SN_TYPE(sn)].arity == 0) ? 1 \
: js::SrcNoteLength(sn))
#define SN_NEXT(sn) ((sn) + SN_LENGTH(sn))
struct JSSrcNoteSpec {
const char* name; /* name for disassembly/debugging output */
int8_t arity; /* number of offset operands */
};
extern JS_FRIEND_DATA(const JSSrcNoteSpec) js_SrcNoteSpec[];
namespace js {
extern JS_FRIEND_API(unsigned)
SrcNoteLength(jssrcnote* sn);
/*
* Get and set the offset operand identified by which (0 for the first, etc.).
*/
extern JS_FRIEND_API(ptrdiff_t)
GetSrcNoteOffset(jssrcnote* sn, unsigned which);
} // namespace js
#endif /* frontend_SourceNotes_h */
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