| /* -*- 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. |
| * |
| * Don't forget to update XDR_BYTECODE_VERSION in vm/Xdr.h for all such |
| * incompatible source note or other bytecode changes. |
| */ |
| #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 */ |
