/[jscoverage]/trunk/js/jsemit.h
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1 siliconforks 332 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
2     * vim: set ts=8 sw=4 et tw=79:
3     *
4     * ***** BEGIN LICENSE BLOCK *****
5     * Version: MPL 1.1/GPL 2.0/LGPL 2.1
6     *
7     * The contents of this file are subject to the Mozilla Public License Version
8     * 1.1 (the "License"); you may not use this file except in compliance with
9     * the License. You may obtain a copy of the License at
10     * http://www.mozilla.org/MPL/
11     *
12     * Software distributed under the License is distributed on an "AS IS" basis,
13     * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
14     * for the specific language governing rights and limitations under the
15     * License.
16     *
17     * The Original Code is Mozilla Communicator client code, released
18     * March 31, 1998.
19     *
20     * The Initial Developer of the Original Code is
21     * Netscape Communications Corporation.
22     * Portions created by the Initial Developer are Copyright (C) 1998
23     * the Initial Developer. All Rights Reserved.
24     *
25     * Contributor(s):
26     *
27     * Alternatively, the contents of this file may be used under the terms of
28     * either of the GNU General Public License Version 2 or later (the "GPL"),
29     * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
30     * in which case the provisions of the GPL or the LGPL are applicable instead
31     * of those above. If you wish to allow use of your version of this file only
32     * under the terms of either the GPL or the LGPL, and not to allow others to
33     * use your version of this file under the terms of the MPL, indicate your
34     * decision by deleting the provisions above and replace them with the notice
35     * and other provisions required by the GPL or the LGPL. If you do not delete
36     * the provisions above, a recipient may use your version of this file under
37     * the terms of any one of the MPL, the GPL or the LGPL.
38     *
39     * ***** END LICENSE BLOCK ***** */
40    
41     #ifndef jsemit_h___
42     #define jsemit_h___
43     /*
44     * JS bytecode generation.
45     */
46    
47     #include "jsstddef.h"
48     #include "jstypes.h"
49     #include "jsatom.h"
50     #include "jsopcode.h"
51     #include "jsscript.h"
52     #include "jsprvtd.h"
53     #include "jspubtd.h"
54    
55     JS_BEGIN_EXTERN_C
56    
57     /*
58     * NB: If you add enumerators for scope statements, add them between STMT_WITH
59     * and STMT_CATCH, or you will break the STMT_TYPE_IS_SCOPE macro. If you add
60     * non-looping statement enumerators, add them before STMT_DO_LOOP or you will
61     * break the STMT_TYPE_IS_LOOP macro.
62     *
63     * Also remember to keep the statementName array in jsemit.c in sync.
64     */
65     typedef enum JSStmtType {
66     STMT_LABEL, /* labeled statement: L: s */
67     STMT_IF, /* if (then) statement */
68     STMT_ELSE, /* else clause of if statement */
69 siliconforks 399 STMT_SEQ, /* synthetic sequence of statements */
70 siliconforks 332 STMT_BLOCK, /* compound statement: { s1[;... sN] } */
71     STMT_SWITCH, /* switch statement */
72     STMT_WITH, /* with statement */
73     STMT_CATCH, /* catch block */
74     STMT_TRY, /* try block */
75     STMT_FINALLY, /* finally block */
76     STMT_SUBROUTINE, /* gosub-target subroutine body */
77     STMT_DO_LOOP, /* do/while loop statement */
78     STMT_FOR_LOOP, /* for loop statement */
79     STMT_FOR_IN_LOOP, /* for/in loop statement */
80     STMT_WHILE_LOOP, /* while loop statement */
81     STMT_LIMIT
82     } JSStmtType;
83    
84     #define STMT_TYPE_IN_RANGE(t,b,e) ((uint)((t) - (b)) <= (uintN)((e) - (b)))
85    
86     /*
87     * A comment on the encoding of the JSStmtType enum and type-testing macros:
88     *
89     * STMT_TYPE_MAYBE_SCOPE tells whether a statement type is always, or may
90     * become, a lexical scope. It therefore includes block and switch (the two
91     * low-numbered "maybe" scope types) and excludes with (with has dynamic scope
92     * pending the "reformed with" in ES4/JS2). It includes all try-catch-finally
93     * types, which are high-numbered maybe-scope types.
94     *
95     * STMT_TYPE_LINKS_SCOPE tells whether a JSStmtInfo of the given type eagerly
96     * links to other scoping statement info records. It excludes the two early
97     * "maybe" types, block and switch, as well as the try and both finally types,
98     * since try and the other trailing maybe-scope types don't need block scope
99     * unless they contain let declarations.
100     *
101     * We treat WITH as a static scope because it prevents lexical binding from
102     * continuing further up the static scope chain. With the lost "reformed with"
103     * proposal for ES4, we would be able to model it statically, too.
104     */
105     #define STMT_TYPE_MAYBE_SCOPE(type) \
106     (type != STMT_WITH && \
107     STMT_TYPE_IN_RANGE(type, STMT_BLOCK, STMT_SUBROUTINE))
108    
109     #define STMT_TYPE_LINKS_SCOPE(type) \
110     STMT_TYPE_IN_RANGE(type, STMT_WITH, STMT_CATCH)
111    
112     #define STMT_TYPE_IS_TRYING(type) \
113     STMT_TYPE_IN_RANGE(type, STMT_TRY, STMT_SUBROUTINE)
114    
115     #define STMT_TYPE_IS_LOOP(type) ((type) >= STMT_DO_LOOP)
116    
117     #define STMT_MAYBE_SCOPE(stmt) STMT_TYPE_MAYBE_SCOPE((stmt)->type)
118     #define STMT_LINKS_SCOPE(stmt) (STMT_TYPE_LINKS_SCOPE((stmt)->type) || \
119     ((stmt)->flags & SIF_SCOPE))
120     #define STMT_IS_TRYING(stmt) STMT_TYPE_IS_TRYING((stmt)->type)
121     #define STMT_IS_LOOP(stmt) STMT_TYPE_IS_LOOP((stmt)->type)
122    
123     typedef struct JSStmtInfo JSStmtInfo;
124    
125     struct JSStmtInfo {
126     uint16 type; /* statement type */
127     uint16 flags; /* flags, see below */
128     ptrdiff_t update; /* loop update offset (top if none) */
129     ptrdiff_t breaks; /* offset of last break in loop */
130     ptrdiff_t continues; /* offset of last continue in loop */
131     union {
132     JSAtom *label; /* name of LABEL */
133     JSObject *blockObj; /* block scope object */
134     } u;
135     JSStmtInfo *down; /* info for enclosing statement */
136     JSStmtInfo *downScope; /* next enclosing lexical scope */
137     };
138    
139     #define SIF_SCOPE 0x0001 /* statement has its own lexical scope */
140     #define SIF_BODY_BLOCK 0x0002 /* STMT_BLOCK type is a function body */
141     #define SIF_FOR_BLOCK 0x0004 /* for (let ...) induced block scope */
142    
143     /*
144     * To reuse space in JSStmtInfo, rename breaks and continues for use during
145     * try/catch/finally code generation and backpatching. To match most common
146     * use cases, the macro argument is a struct, not a struct pointer. Only a
147     * loop, switch, or label statement info record can have breaks and continues,
148     * and only a for loop has an update backpatch chain, so it's safe to overlay
149     * these for the "trying" JSStmtTypes.
150     */
151     #define CATCHNOTE(stmt) ((stmt).update)
152     #define GOSUBS(stmt) ((stmt).breaks)
153     #define GUARDJUMP(stmt) ((stmt).continues)
154    
155     #define AT_TOP_LEVEL(tc) \
156     (!(tc)->topStmt || ((tc)->topStmt->flags & SIF_BODY_BLOCK))
157    
158     #define SET_STATEMENT_TOP(stmt, top) \
159     ((stmt)->update = (top), (stmt)->breaks = (stmt)->continues = (-1))
160    
161     struct JSTreeContext { /* tree context for semantic checks */
162     uint16 flags; /* statement state flags, see below */
163     uint16 ngvars; /* max. no. of global variables/regexps */
164     JSStmtInfo *topStmt; /* top of statement info stack */
165     JSStmtInfo *topScopeStmt; /* top lexical scope statement */
166     JSObject *blockChain; /* compile time block scope chain (NB: one
167     deeper than the topScopeStmt/downScope
168     chain when in head of let block/expr) */
169     JSParseNode *blockNode; /* parse node for a lexical scope.
170     XXX combine with blockChain? */
171     JSAtomList decls; /* function, const, and var declarations */
172     JSParseContext *parseContext;
173    
174     union {
175    
176     JSFunction *fun; /* function to store argument and variable
177     names when flags & TCF_IN_FUNCTION */
178     JSObject *scopeChain; /* scope chain object for the script */
179     } u;
180    
181     #ifdef JS_SCOPE_DEPTH_METER
182     uint16 scopeDepth; /* current lexical scope chain depth */
183     uint16 maxScopeDepth; /* maximum lexical scope chain depth */
184     #endif
185     };
186    
187     #define TCF_IN_FUNCTION 0x01 /* parsing inside function body */
188     #define TCF_RETURN_EXPR 0x02 /* function has 'return expr;' */
189     #define TCF_RETURN_VOID 0x04 /* function has 'return;' */
190     #define TCF_IN_FOR_INIT 0x08 /* parsing init expr of for; exclude 'in' */
191     #define TCF_FUN_CLOSURE_VS_VAR 0x10 /* function and var with same name */
192     #define TCF_FUN_USES_NONLOCALS 0x20 /* function refers to non-local names */
193     #define TCF_FUN_HEAVYWEIGHT 0x40 /* function needs Call object per call */
194     #define TCF_FUN_IS_GENERATOR 0x80 /* parsed yield statement in function */
195     #define TCF_HAS_DEFXMLNS 0x100 /* default xml namespace = ...; parsed */
196     #define TCF_HAS_FUNCTION_STMT 0x200 /* block contains a function statement */
197     #define TCF_GENEXP_LAMBDA 0x400 /* flag lambda from generator expression */
198     #define TCF_COMPILE_N_GO 0x800 /* compiler-and-go mode of script, can
199     optimize name references based on scope
200     chain */
201     #define TCF_NO_SCRIPT_RVAL 0x1000 /* API caller does not want result value
202     from global script */
203     /*
204     * Flags to propagate out of the blocks.
205     */
206     #define TCF_RETURN_FLAGS (TCF_RETURN_EXPR | TCF_RETURN_VOID)
207    
208     /*
209     * Flags to propagate from FunctionBody.
210     */
211     #define TCF_FUN_FLAGS (TCF_FUN_IS_GENERATOR | \
212     TCF_FUN_HEAVYWEIGHT | \
213     TCF_FUN_USES_NONLOCALS | \
214     TCF_FUN_CLOSURE_VS_VAR)
215    
216     /*
217     * Flags field, not stored in JSTreeContext.flags, for passing staticDepth
218     * into js_CompileScript.
219     */
220     #define TCF_STATIC_DEPTH_MASK 0xffff0000
221     #define TCF_GET_STATIC_DEPTH(f) ((uint32)(f) >> 16)
222     #define TCF_PUT_STATIC_DEPTH(d) ((uint16)(d) << 16)
223    
224     #ifdef JS_SCOPE_DEPTH_METER
225     # define JS_SCOPE_DEPTH_METERING(code) ((void) (code))
226     #else
227     # define JS_SCOPE_DEPTH_METERING(code) ((void) 0)
228     #endif
229    
230     #define TREE_CONTEXT_INIT(tc, pc) \
231     ((tc)->flags = (tc)->ngvars = 0, \
232     (tc)->topStmt = (tc)->topScopeStmt = NULL, \
233     (tc)->blockChain = NULL, \
234     ATOM_LIST_INIT(&(tc)->decls), \
235     (tc)->blockNode = NULL, \
236     (tc)->parseContext = (pc), \
237     (tc)->u.scopeChain = NULL, \
238     JS_SCOPE_DEPTH_METERING((tc)->scopeDepth = (tc)->maxScopeDepth = 0))
239    
240     /*
241     * For functions TREE_CONTEXT_FINISH is called the second time to finish the
242     * extra tc created during code generation. We skip stats update in such
243     * cases.
244     */
245     #define TREE_CONTEXT_FINISH(cx, tc) \
246     JS_SCOPE_DEPTH_METERING( \
247     (tc)->maxScopeDepth == (uintN) -1 || \
248     JS_BASIC_STATS_ACCUM(&(cx)->runtime->lexicalScopeDepthStats, \
249     (tc)->maxScopeDepth))
250    
251     /*
252     * Span-dependent instructions are jumps whose span (from the jump bytecode to
253     * the jump target) may require 2 or 4 bytes of immediate operand.
254     */
255     typedef struct JSSpanDep JSSpanDep;
256     typedef struct JSJumpTarget JSJumpTarget;
257    
258     struct JSSpanDep {
259     ptrdiff_t top; /* offset of first bytecode in an opcode */
260     ptrdiff_t offset; /* offset - 1 within opcode of jump operand */
261     ptrdiff_t before; /* original offset - 1 of jump operand */
262     JSJumpTarget *target; /* tagged target pointer or backpatch delta */
263     };
264    
265     /*
266     * Jump targets are stored in an AVL tree, for O(log(n)) lookup with targets
267     * sorted by offset from left to right, so that targets after a span-dependent
268     * instruction whose jump offset operand must be extended can be found quickly
269     * and adjusted upward (toward higher offsets).
270     */
271     struct JSJumpTarget {
272     ptrdiff_t offset; /* offset of span-dependent jump target */
273     int balance; /* AVL tree balance number */
274     JSJumpTarget *kids[2]; /* left and right AVL tree child pointers */
275     };
276    
277     #define JT_LEFT 0
278     #define JT_RIGHT 1
279     #define JT_OTHER_DIR(dir) (1 - (dir))
280     #define JT_IMBALANCE(dir) (((dir) << 1) - 1)
281     #define JT_DIR(imbalance) (((imbalance) + 1) >> 1)
282    
283     /*
284     * Backpatch deltas are encoded in JSSpanDep.target if JT_TAG_BIT is clear,
285     * so we can maintain backpatch chains when using span dependency records to
286     * hold jump offsets that overflow 16 bits.
287     */
288     #define JT_TAG_BIT ((jsword) 1)
289     #define JT_UNTAG_SHIFT 1
290     #define JT_SET_TAG(jt) ((JSJumpTarget *)((jsword)(jt) | JT_TAG_BIT))
291     #define JT_CLR_TAG(jt) ((JSJumpTarget *)((jsword)(jt) & ~JT_TAG_BIT))
292     #define JT_HAS_TAG(jt) ((jsword)(jt) & JT_TAG_BIT)
293    
294     #define BITS_PER_PTRDIFF (sizeof(ptrdiff_t) * JS_BITS_PER_BYTE)
295     #define BITS_PER_BPDELTA (BITS_PER_PTRDIFF - 1 - JT_UNTAG_SHIFT)
296     #define BPDELTA_MAX (((ptrdiff_t)1 << BITS_PER_BPDELTA) - 1)
297     #define BPDELTA_TO_JT(bp) ((JSJumpTarget *)((bp) << JT_UNTAG_SHIFT))
298     #define JT_TO_BPDELTA(jt) ((ptrdiff_t)((jsword)(jt) >> JT_UNTAG_SHIFT))
299    
300     #define SD_SET_TARGET(sd,jt) ((sd)->target = JT_SET_TAG(jt))
301     #define SD_GET_TARGET(sd) (JS_ASSERT(JT_HAS_TAG((sd)->target)), \
302     JT_CLR_TAG((sd)->target))
303     #define SD_SET_BPDELTA(sd,bp) ((sd)->target = BPDELTA_TO_JT(bp))
304     #define SD_GET_BPDELTA(sd) (JS_ASSERT(!JT_HAS_TAG((sd)->target)), \
305     JT_TO_BPDELTA((sd)->target))
306    
307     /* Avoid asserting twice by expanding SD_GET_TARGET in the "then" clause. */
308     #define SD_SPAN(sd,pivot) (SD_GET_TARGET(sd) \
309     ? JT_CLR_TAG((sd)->target)->offset - (pivot) \
310     : 0)
311    
312     typedef struct JSTryNode JSTryNode;
313    
314     struct JSTryNode {
315     JSTryNote note;
316     JSTryNode *prev;
317     };
318    
319     typedef struct JSEmittedObjectList {
320     uint32 length; /* number of emitted so far objects */
321     JSParsedObjectBox *lastPob; /* last emitted object */
322     } JSEmittedObjectList;
323    
324     extern void
325     FinishParsedObjects(JSEmittedObjectList *emittedList, JSObjectArray *objectMap);
326    
327     struct JSCodeGenerator {
328     JSTreeContext treeContext; /* base state: statement info stack, etc. */
329    
330     JSArenaPool *codePool; /* pointer to thread code arena pool */
331     JSArenaPool *notePool; /* pointer to thread srcnote arena pool */
332     void *codeMark; /* low watermark in cg->codePool */
333     void *noteMark; /* low watermark in cg->notePool */
334    
335     struct {
336     jsbytecode *base; /* base of JS bytecode vector */
337     jsbytecode *limit; /* one byte beyond end of bytecode */
338     jsbytecode *next; /* pointer to next free bytecode */
339     jssrcnote *notes; /* source notes, see below */
340     uintN noteCount; /* number of source notes so far */
341     uintN noteMask; /* growth increment for notes */
342     ptrdiff_t lastNoteOffset; /* code offset for last source note */
343     uintN currentLine; /* line number for tree-based srcnote gen */
344     } prolog, main, *current;
345    
346     JSAtomList atomList; /* literals indexed for mapping */
347     uintN firstLine; /* first line, for js_NewScriptFromCG */
348    
349     intN stackDepth; /* current stack depth in script frame */
350     uintN maxStackDepth; /* maximum stack depth so far */
351    
352     uintN ntrynotes; /* number of allocated so far try notes */
353     JSTryNode *lastTryNode; /* the last allocated try node */
354    
355     JSSpanDep *spanDeps; /* span dependent instruction records */
356     JSJumpTarget *jumpTargets; /* AVL tree of jump target offsets */
357     JSJumpTarget *jtFreeList; /* JT_LEFT-linked list of free structs */
358     uintN numSpanDeps; /* number of span dependencies */
359     uintN numJumpTargets; /* number of jump targets */
360     ptrdiff_t spanDepTodo; /* offset from main.base of potentially
361     unoptimized spandeps */
362    
363     uintN arrayCompDepth; /* stack depth of array in comprehension */
364    
365     uintN emitLevel; /* js_EmitTree recursion level */
366     JSAtomList constList; /* compile time constants */
367    
368     JSEmittedObjectList objectList; /* list of emitted so far objects */
369     JSEmittedObjectList regexpList; /* list of emitted so far regexp
370     that will be cloned during execution */
371    
372     uintN staticDepth; /* static frame chain depth */
373     JSAtomList upvarList; /* map of atoms to upvar indexes */
374     JSUpvarArray upvarMap; /* indexed upvar pairs (JS_realloc'ed) */
375     JSCodeGenerator *parent; /* enclosing function or global context */
376     };
377    
378     #define CG_TS(cg) TS((cg)->treeContext.parseContext)
379    
380     #define CG_BASE(cg) ((cg)->current->base)
381     #define CG_LIMIT(cg) ((cg)->current->limit)
382     #define CG_NEXT(cg) ((cg)->current->next)
383     #define CG_CODE(cg,offset) (CG_BASE(cg) + (offset))
384     #define CG_OFFSET(cg) PTRDIFF(CG_NEXT(cg), CG_BASE(cg), jsbytecode)
385    
386     #define CG_NOTES(cg) ((cg)->current->notes)
387     #define CG_NOTE_COUNT(cg) ((cg)->current->noteCount)
388     #define CG_NOTE_MASK(cg) ((cg)->current->noteMask)
389     #define CG_LAST_NOTE_OFFSET(cg) ((cg)->current->lastNoteOffset)
390     #define CG_CURRENT_LINE(cg) ((cg)->current->currentLine)
391    
392     #define CG_PROLOG_BASE(cg) ((cg)->prolog.base)
393     #define CG_PROLOG_LIMIT(cg) ((cg)->prolog.limit)
394     #define CG_PROLOG_NEXT(cg) ((cg)->prolog.next)
395     #define CG_PROLOG_CODE(cg,poff) (CG_PROLOG_BASE(cg) + (poff))
396     #define CG_PROLOG_OFFSET(cg) PTRDIFF(CG_PROLOG_NEXT(cg), CG_PROLOG_BASE(cg),\
397     jsbytecode)
398    
399     #define CG_SWITCH_TO_MAIN(cg) ((cg)->current = &(cg)->main)
400     #define CG_SWITCH_TO_PROLOG(cg) ((cg)->current = &(cg)->prolog)
401    
402     /*
403     * Initialize cg to allocate bytecode space from codePool, source note space
404     * from notePool, and all other arena-allocated temporaries from cx->tempPool.
405     */
406     extern JS_FRIEND_API(void)
407     js_InitCodeGenerator(JSContext *cx, JSCodeGenerator *cg, JSParseContext *pc,
408     JSArenaPool *codePool, JSArenaPool *notePool,
409     uintN lineno);
410    
411     /*
412     * Release cg->codePool, cg->notePool, and cx->tempPool to marks set by
413     * js_InitCodeGenerator. Note that cgs are magic: they own the arena pool
414     * "tops-of-stack" space above their codeMark, noteMark, and tempMark points.
415     * This means you cannot alloc from tempPool and save the pointer beyond the
416     * next JS_FinishCodeGenerator.
417     */
418     extern JS_FRIEND_API(void)
419     js_FinishCodeGenerator(JSContext *cx, JSCodeGenerator *cg);
420    
421     /*
422     * Emit one bytecode.
423     */
424     extern ptrdiff_t
425     js_Emit1(JSContext *cx, JSCodeGenerator *cg, JSOp op);
426    
427     /*
428     * Emit two bytecodes, an opcode (op) with a byte of immediate operand (op1).
429     */
430     extern ptrdiff_t
431     js_Emit2(JSContext *cx, JSCodeGenerator *cg, JSOp op, jsbytecode op1);
432    
433     /*
434     * Emit three bytecodes, an opcode with two bytes of immediate operands.
435     */
436     extern ptrdiff_t
437     js_Emit3(JSContext *cx, JSCodeGenerator *cg, JSOp op, jsbytecode op1,
438     jsbytecode op2);
439    
440     /*
441     * Emit (1 + extra) bytecodes, for N bytes of op and its immediate operand.
442     */
443     extern ptrdiff_t
444     js_EmitN(JSContext *cx, JSCodeGenerator *cg, JSOp op, size_t extra);
445    
446     /*
447     * Unsafe macro to call js_SetJumpOffset and return false if it does.
448     */
449     #define CHECK_AND_SET_JUMP_OFFSET_CUSTOM(cx,cg,pc,off,BAD_EXIT) \
450     JS_BEGIN_MACRO \
451     if (!js_SetJumpOffset(cx, cg, pc, off)) { \
452     BAD_EXIT; \
453     } \
454     JS_END_MACRO
455    
456     #define CHECK_AND_SET_JUMP_OFFSET(cx,cg,pc,off) \
457     CHECK_AND_SET_JUMP_OFFSET_CUSTOM(cx,cg,pc,off,return JS_FALSE)
458    
459     #define CHECK_AND_SET_JUMP_OFFSET_AT_CUSTOM(cx,cg,off,BAD_EXIT) \
460     CHECK_AND_SET_JUMP_OFFSET_CUSTOM(cx, cg, CG_CODE(cg,off), \
461     CG_OFFSET(cg) - (off), BAD_EXIT)
462    
463     #define CHECK_AND_SET_JUMP_OFFSET_AT(cx,cg,off) \
464     CHECK_AND_SET_JUMP_OFFSET_AT_CUSTOM(cx, cg, off, return JS_FALSE)
465    
466     extern JSBool
467     js_SetJumpOffset(JSContext *cx, JSCodeGenerator *cg, jsbytecode *pc,
468     ptrdiff_t off);
469    
470     /* Test whether we're in a statement of given type. */
471     extern JSBool
472     js_InStatement(JSTreeContext *tc, JSStmtType type);
473    
474     /* Test whether we're in a with statement. */
475     #define js_InWithStatement(tc) js_InStatement(tc, STMT_WITH)
476    
477     /*
478     * Push the C-stack-allocated struct at stmt onto the stmtInfo stack.
479     */
480     extern void
481     js_PushStatement(JSTreeContext *tc, JSStmtInfo *stmt, JSStmtType type,
482     ptrdiff_t top);
483    
484     /*
485     * Push a block scope statement and link blockObj into tc->blockChain. To pop
486     * this statement info record, use js_PopStatement as usual, or if appropriate
487     * (if generating code), js_PopStatementCG.
488     */
489     extern void
490     js_PushBlockScope(JSTreeContext *tc, JSStmtInfo *stmt, JSObject *blockObj,
491     ptrdiff_t top);
492    
493     /*
494     * Pop tc->topStmt. If the top JSStmtInfo struct is not stack-allocated, it
495     * is up to the caller to free it.
496     */
497     extern void
498     js_PopStatement(JSTreeContext *tc);
499    
500     /*
501     * Like js_PopStatement(&cg->treeContext), also patch breaks and continues
502     * unless the top statement info record represents a try-catch-finally suite.
503     * May fail if a jump offset overflows.
504     */
505     extern JSBool
506     js_PopStatementCG(JSContext *cx, JSCodeGenerator *cg);
507    
508     /*
509     * Define and lookup a primitive jsval associated with the const named by atom.
510     * js_DefineCompileTimeConstant analyzes the constant-folded initializer at pn
511     * and saves the const's value in cg->constList, if it can be used at compile
512     * time. It returns true unless an error occurred.
513     *
514     * If the initializer's value could not be saved, js_DefineCompileTimeConstant
515     * calls will return the undefined value. js_DefineCompileTimeConstant tries
516     * to find a const value memorized for atom, returning true with *vp set to a
517     * value other than undefined if the constant was found, true with *vp set to
518     * JSVAL_VOID if not found, and false on error.
519     */
520     extern JSBool
521     js_DefineCompileTimeConstant(JSContext *cx, JSCodeGenerator *cg, JSAtom *atom,
522     JSParseNode *pn);
523    
524     /*
525     * Find a lexically scoped variable (one declared by let, catch, or an array
526     * comprehension) named by atom, looking in tc's compile-time scopes.
527     *
528     * If a WITH statement is reached along the scope stack, return its statement
529     * info record, so callers can tell that atom is ambiguous. If slotp is not
530     * null, then if atom is found, set *slotp to its stack slot, otherwise to -1.
531     * This means that if slotp is not null, all the block objects on the lexical
532     * scope chain must have had their depth slots computed by the code generator,
533     * so the caller must be under js_EmitTree.
534     *
535     * In any event, directly return the statement info record in which atom was
536     * found. Otherwise return null.
537     */
538     extern JSStmtInfo *
539     js_LexicalLookup(JSTreeContext *tc, JSAtom *atom, jsint *slotp);
540    
541     /*
542     * Emit code into cg for the tree rooted at pn.
543     */
544     extern JSBool
545     js_EmitTree(JSContext *cx, JSCodeGenerator *cg, JSParseNode *pn);
546    
547     /*
548     * Emit function code using cg for the tree rooted at body.
549     */
550     extern JSBool
551     js_EmitFunctionScript(JSContext *cx, JSCodeGenerator *cg, JSParseNode *body);
552    
553     /*
554     * Source notes generated along with bytecode for decompiling and debugging.
555     * A source note is a uint8 with 5 bits of type and 3 of offset from the pc of
556     * the previous note. If 3 bits of offset aren't enough, extended delta notes
557     * (SRC_XDELTA) consisting of 2 set high order bits followed by 6 offset bits
558     * are emitted before the next note. Some notes have operand offsets encoded
559     * immediately after them, in note bytes or byte-triples.
560     *
561     * Source Note Extended Delta
562     * +7-6-5-4-3+2-1-0+ +7-6-5+4-3-2-1-0+
563     * |note-type|delta| |1 1| ext-delta |
564     * +---------+-----+ +---+-----------+
565     *
566     * At most one "gettable" note (i.e., a note of type other than SRC_NEWLINE,
567     * SRC_SETLINE, and SRC_XDELTA) applies to a given bytecode.
568     *
569     * NB: the js_SrcNoteSpec array in jsemit.c is indexed by this enum, so its
570     * initializers need to match the order here.
571     *
572     * Note on adding new source notes: every pair of bytecodes (A, B) where A and
573     * B have disjoint sets of source notes that could apply to each bytecode may
574     * reuse the same note type value for two notes (snA, snB) that have the same
575     * arity, offsetBias, and isSpanDep initializers in js_SrcNoteSpec. This is
576     * why SRC_IF and SRC_INITPROP have the same value below. For bad historical
577     * reasons, some bytecodes below that could be overlayed have not been, but
578     * before using SRC_EXTENDED, consider compressing the existing note types.
579     *
580     * Don't forget to update JSXDR_BYTECODE_VERSION in jsxdrapi.h for all such
581     * incompatible source note or other bytecode changes.
582     */
583     typedef enum JSSrcNoteType {
584     SRC_NULL = 0, /* terminates a note vector */
585     SRC_IF = 1, /* JSOP_IFEQ bytecode is from an if-then */
586     SRC_BREAK = 1, /* JSOP_GOTO is a break */
587     SRC_INITPROP = 1, /* disjoint meaning applied to JSOP_INITELEM or
588     to an index label in a regular (structuring)
589     or a destructuring object initialiser */
590     SRC_GENEXP = 1, /* JSOP_ANONFUNOBJ from generator expression */
591     SRC_IF_ELSE = 2, /* JSOP_IFEQ bytecode is from an if-then-else */
592 siliconforks 399 SRC_FOR_IN = 2, /* JSOP_GOTO to for-in loop condition from
593     before loop (same arity as SRC_IF_ELSE) */
594     SRC_FOR = 3, /* JSOP_NOP or JSOP_POP in for(;;) loop head */
595     SRC_WHILE = 4, /* JSOP_GOTO to for or while loop condition
596     from before loop, else JSOP_NOP at top of
597     do-while loop */
598 siliconforks 332 SRC_CONTINUE = 5, /* JSOP_GOTO is a continue, not a break;
599     also used on JSOP_ENDINIT if extra comma
600     at end of array literal: [1,2,,] */
601     SRC_DECL = 6, /* type of a declaration (var, const, let*) */
602     SRC_DESTRUCT = 6, /* JSOP_DUP starting a destructuring assignment
603     operation, with SRC_DECL_* offset operand */
604     SRC_PCDELTA = 7, /* distance forward from comma-operator to
605     next POP, or from CONDSWITCH to first CASE
606     opcode, etc. -- always a forward delta */
607     SRC_GROUPASSIGN = 7, /* SRC_DESTRUCT variant for [a, b] = [c, d] */
608     SRC_ASSIGNOP = 8, /* += or another assign-op follows */
609     SRC_COND = 9, /* JSOP_IFEQ is from conditional ?: operator */
610     SRC_BRACE = 10, /* mandatory brace, for scope or to avoid
611     dangling else */
612     SRC_HIDDEN = 11, /* opcode shouldn't be decompiled */
613     SRC_PCBASE = 12, /* distance back from annotated getprop or
614     setprop op to left-most obj.prop.subprop
615     bytecode -- always a backward delta */
616     SRC_LABEL = 13, /* JSOP_NOP for label: with atomid immediate */
617     SRC_LABELBRACE = 14, /* JSOP_NOP for label: {...} begin brace */
618     SRC_ENDBRACE = 15, /* JSOP_NOP for label: {...} end brace */
619     SRC_BREAK2LABEL = 16, /* JSOP_GOTO for 'break label' with atomid */
620     SRC_CONT2LABEL = 17, /* JSOP_GOTO for 'continue label' with atomid */
621     SRC_SWITCH = 18, /* JSOP_*SWITCH with offset to end of switch,
622     2nd off to first JSOP_CASE if condswitch */
623     SRC_FUNCDEF = 19, /* JSOP_NOP for function f() with atomid */
624     SRC_CATCH = 20, /* catch block has guard */
625     SRC_EXTENDED = 21, /* extended source note, 32-159, in next byte */
626     SRC_NEWLINE = 22, /* bytecode follows a source newline */
627     SRC_SETLINE = 23, /* a file-absolute source line number note */
628     SRC_XDELTA = 24 /* 24-31 are for extended delta notes */
629     } JSSrcNoteType;
630    
631     /*
632     * Constants for the SRC_DECL source note. Note that span-dependent bytecode
633     * selection means that any SRC_DECL offset greater than SRC_DECL_LET may need
634     * to be adjusted, but these "offsets" are too small to span a span-dependent
635     * instruction, so can be used to denote distinct declaration syntaxes to the
636     * decompiler.
637     *
638     * NB: the var_prefix array in jsopcode.c depends on these dense indexes from
639     * SRC_DECL_VAR through SRC_DECL_LET.
640     */
641     #define SRC_DECL_VAR 0
642     #define SRC_DECL_CONST 1
643     #define SRC_DECL_LET 2
644     #define SRC_DECL_NONE 3
645    
646     #define SN_TYPE_BITS 5
647     #define SN_DELTA_BITS 3
648     #define SN_XDELTA_BITS 6
649     #define SN_TYPE_MASK (JS_BITMASK(SN_TYPE_BITS) << SN_DELTA_BITS)
650     #define SN_DELTA_MASK ((ptrdiff_t)JS_BITMASK(SN_DELTA_BITS))
651     #define SN_XDELTA_MASK ((ptrdiff_t)JS_BITMASK(SN_XDELTA_BITS))
652    
653     #define SN_MAKE_NOTE(sn,t,d) (*(sn) = (jssrcnote) \
654     (((t) << SN_DELTA_BITS) \
655     | ((d) & SN_DELTA_MASK)))
656     #define SN_MAKE_XDELTA(sn,d) (*(sn) = (jssrcnote) \
657     ((SRC_XDELTA << SN_DELTA_BITS) \
658     | ((d) & SN_XDELTA_MASK)))
659    
660     #define SN_IS_XDELTA(sn) ((*(sn) >> SN_DELTA_BITS) >= SRC_XDELTA)
661     #define SN_TYPE(sn) ((JSSrcNoteType)(SN_IS_XDELTA(sn) \
662     ? SRC_XDELTA \
663     : *(sn) >> SN_DELTA_BITS))
664     #define SN_SET_TYPE(sn,type) SN_MAKE_NOTE(sn, type, SN_DELTA(sn))
665     #define SN_IS_GETTABLE(sn) (SN_TYPE(sn) < SRC_NEWLINE)
666    
667     #define SN_DELTA(sn) ((ptrdiff_t)(SN_IS_XDELTA(sn) \
668     ? *(sn) & SN_XDELTA_MASK \
669     : *(sn) & SN_DELTA_MASK))
670     #define SN_SET_DELTA(sn,delta) (SN_IS_XDELTA(sn) \
671     ? SN_MAKE_XDELTA(sn, delta) \
672     : SN_MAKE_NOTE(sn, SN_TYPE(sn), delta))
673    
674     #define SN_DELTA_LIMIT ((ptrdiff_t)JS_BIT(SN_DELTA_BITS))
675     #define SN_XDELTA_LIMIT ((ptrdiff_t)JS_BIT(SN_XDELTA_BITS))
676    
677     /*
678     * Offset fields follow certain notes and are frequency-encoded: an offset in
679     * [0,0x7f] consumes one byte, an offset in [0x80,0x7fffff] takes three, and
680     * the high bit of the first byte is set.
681     */
682     #define SN_3BYTE_OFFSET_FLAG 0x80
683     #define SN_3BYTE_OFFSET_MASK 0x7f
684    
685     typedef struct JSSrcNoteSpec {
686     const char *name; /* name for disassembly/debugging output */
687     int8 arity; /* number of offset operands */
688     uint8 offsetBias; /* bias of offset(s) from annotated pc */
689     int8 isSpanDep; /* 1 or -1 if offsets could span extended ops,
690     0 otherwise; sign tells span direction */
691     } JSSrcNoteSpec;
692    
693     extern JS_FRIEND_DATA(JSSrcNoteSpec) js_SrcNoteSpec[];
694     extern JS_FRIEND_API(uintN) js_SrcNoteLength(jssrcnote *sn);
695    
696     #define SN_LENGTH(sn) ((js_SrcNoteSpec[SN_TYPE(sn)].arity == 0) ? 1 \
697     : js_SrcNoteLength(sn))
698     #define SN_NEXT(sn) ((sn) + SN_LENGTH(sn))
699    
700     /* A source note array is terminated by an all-zero element. */
701     #define SN_MAKE_TERMINATOR(sn) (*(sn) = SRC_NULL)
702     #define SN_IS_TERMINATOR(sn) (*(sn) == SRC_NULL)
703    
704     /*
705     * Append a new source note of the given type (and therefore size) to cg's
706     * notes dynamic array, updating cg->noteCount. Return the new note's index
707     * within the array pointed at by cg->current->notes. Return -1 if out of
708     * memory.
709     */
710     extern intN
711     js_NewSrcNote(JSContext *cx, JSCodeGenerator *cg, JSSrcNoteType type);
712    
713     extern intN
714     js_NewSrcNote2(JSContext *cx, JSCodeGenerator *cg, JSSrcNoteType type,
715     ptrdiff_t offset);
716    
717     extern intN
718     js_NewSrcNote3(JSContext *cx, JSCodeGenerator *cg, JSSrcNoteType type,
719     ptrdiff_t offset1, ptrdiff_t offset2);
720    
721     /*
722     * NB: this function can add at most one extra extended delta note.
723     */
724     extern jssrcnote *
725     js_AddToSrcNoteDelta(JSContext *cx, JSCodeGenerator *cg, jssrcnote *sn,
726     ptrdiff_t delta);
727    
728     /*
729     * Get and set the offset operand identified by which (0 for the first, etc.).
730     */
731     extern JS_FRIEND_API(ptrdiff_t)
732     js_GetSrcNoteOffset(jssrcnote *sn, uintN which);
733    
734     extern JSBool
735     js_SetSrcNoteOffset(JSContext *cx, JSCodeGenerator *cg, uintN index,
736     uintN which, ptrdiff_t offset);
737    
738     /*
739     * Finish taking source notes in cx's notePool, copying final notes to the new
740     * stable store allocated by the caller and passed in via notes. Return false
741     * on malloc failure, which means this function reported an error.
742     *
743     * To compute the number of jssrcnotes to allocate and pass in via notes, use
744     * the CG_COUNT_FINAL_SRCNOTES macro. This macro knows a lot about details of
745     * js_FinishTakingSrcNotes, SO DON'T CHANGE jsemit.c's js_FinishTakingSrcNotes
746     * FUNCTION WITHOUT CHECKING WHETHER THIS MACRO NEEDS CORRESPONDING CHANGES!
747     */
748     #define CG_COUNT_FINAL_SRCNOTES(cg, cnt) \
749     JS_BEGIN_MACRO \
750     ptrdiff_t diff_ = CG_PROLOG_OFFSET(cg) - (cg)->prolog.lastNoteOffset; \
751     cnt = (cg)->prolog.noteCount + (cg)->main.noteCount + 1; \
752     if ((cg)->prolog.noteCount && \
753     (cg)->prolog.currentLine != (cg)->firstLine) { \
754     if (diff_ > SN_DELTA_MASK) \
755     cnt += JS_HOWMANY(diff_ - SN_DELTA_MASK, SN_XDELTA_MASK); \
756     cnt += 2 + (((cg)->firstLine > SN_3BYTE_OFFSET_MASK) << 1); \
757     } else if (diff_ > 0) { \
758     if (cg->main.noteCount) { \
759     jssrcnote *sn_ = (cg)->main.notes; \
760     diff_ -= SN_IS_XDELTA(sn_) \
761     ? SN_XDELTA_MASK - (*sn_ & SN_XDELTA_MASK) \
762     : SN_DELTA_MASK - (*sn_ & SN_DELTA_MASK); \
763     } \
764     if (diff_ > 0) \
765     cnt += JS_HOWMANY(diff_, SN_XDELTA_MASK); \
766     } \
767     JS_END_MACRO
768    
769     extern JSBool
770     js_FinishTakingSrcNotes(JSContext *cx, JSCodeGenerator *cg, jssrcnote *notes);
771    
772     extern void
773     js_FinishTakingTryNotes(JSCodeGenerator *cg, JSTryNoteArray *array);
774    
775     JS_END_EXTERN_C
776    
777     #endif /* jsemit_h___ */

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