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Diffstat (limited to 'js/src/frontend/SourceNotes.h')
| -rw-r--r-- | js/src/frontend/SourceNotes.h | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/js/src/frontend/SourceNotes.h b/js/src/frontend/SourceNotes.h new file mode 100644 index 000000000..dd2a95ad1 --- /dev/null +++ b/js/src/frontend/SourceNotes.h @@ -0,0 +1,207 @@ +/* -*- 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_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_UNUSED20, "unused20", 0) /* Unused. */ \ + 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 */ |