1 /*
2 ** Common definitions for the JIT compiler.
3 ** Copyright (C) 2005-2021 Mike Pall. See Copyright Notice in luajit.h
4 */
5 
6 #ifndef _LJ_JIT_H
7 #define _LJ_JIT_H
8 
9 #include "lj_obj.h"
10 #include "lj_ir.h"
11 
12 /* -- JIT engine flags ---------------------------------------------------- */
13 
14 /* General JIT engine flags. 4 bits. */
15 #define JIT_F_ON		0x00000001
16 
17 /* CPU-specific JIT engine flags. 12 bits. Flags and strings must match. */
18 #define JIT_F_CPU		0x00000010
19 
20 #if LJ_TARGET_X86ORX64
21 
22 #define JIT_F_SSE3		(JIT_F_CPU << 0)
23 #define JIT_F_SSE4_1		(JIT_F_CPU << 1)
24 #define JIT_F_BMI2		(JIT_F_CPU << 2)
25 
26 
27 #define JIT_F_CPUSTRING		"\4SSE3\6SSE4.1\4BMI2"
28 
29 #elif LJ_TARGET_ARM
30 
31 #define JIT_F_ARMV6_		(JIT_F_CPU << 0)
32 #define JIT_F_ARMV6T2_		(JIT_F_CPU << 1)
33 #define JIT_F_ARMV7		(JIT_F_CPU << 2)
34 #define JIT_F_ARMV8		(JIT_F_CPU << 3)
35 #define JIT_F_VFPV2		(JIT_F_CPU << 4)
36 #define JIT_F_VFPV3		(JIT_F_CPU << 5)
37 
38 #define JIT_F_ARMV6		(JIT_F_ARMV6_|JIT_F_ARMV6T2_|JIT_F_ARMV7|JIT_F_ARMV8)
39 #define JIT_F_ARMV6T2		(JIT_F_ARMV6T2_|JIT_F_ARMV7|JIT_F_ARMV8)
40 #define JIT_F_VFP		(JIT_F_VFPV2|JIT_F_VFPV3)
41 
42 #define JIT_F_CPUSTRING		"\5ARMv6\7ARMv6T2\5ARMv7\5ARMv8\5VFPv2\5VFPv3"
43 
44 #elif LJ_TARGET_PPC
45 
46 #define JIT_F_SQRT		(JIT_F_CPU << 0)
47 #define JIT_F_ROUND		(JIT_F_CPU << 1)
48 
49 #define JIT_F_CPUSTRING		"\4SQRT\5ROUND"
50 
51 #elif LJ_TARGET_MIPS
52 
53 #define JIT_F_MIPSXXR2		(JIT_F_CPU << 0)
54 
55 #if LJ_TARGET_MIPS32
56 #if LJ_TARGET_MIPSR6
57 #define JIT_F_CPUSTRING		"\010MIPS32R6"
58 #else
59 #define JIT_F_CPUSTRING		"\010MIPS32R2"
60 #endif
61 #else
62 #if LJ_TARGET_MIPSR6
63 #define JIT_F_CPUSTRING		"\010MIPS64R6"
64 #else
65 #define JIT_F_CPUSTRING		"\010MIPS64R2"
66 #endif
67 #endif
68 
69 #else
70 
71 #define JIT_F_CPUSTRING		""
72 
73 #endif
74 
75 /* Optimization flags. 12 bits. */
76 #define JIT_F_OPT		0x00010000
77 #define JIT_F_OPT_MASK		0x0fff0000
78 
79 #define JIT_F_OPT_FOLD		(JIT_F_OPT << 0)
80 #define JIT_F_OPT_CSE		(JIT_F_OPT << 1)
81 #define JIT_F_OPT_DCE		(JIT_F_OPT << 2)
82 #define JIT_F_OPT_FWD		(JIT_F_OPT << 3)
83 #define JIT_F_OPT_DSE		(JIT_F_OPT << 4)
84 #define JIT_F_OPT_NARROW	(JIT_F_OPT << 5)
85 #define JIT_F_OPT_LOOP		(JIT_F_OPT << 6)
86 #define JIT_F_OPT_ABC		(JIT_F_OPT << 7)
87 #define JIT_F_OPT_SINK		(JIT_F_OPT << 8)
88 #define JIT_F_OPT_FUSE		(JIT_F_OPT << 9)
89 
90 /* Optimizations names for -O. Must match the order above. */
91 #define JIT_F_OPTSTRING	\
92   "\4fold\3cse\3dce\3fwd\3dse\6narrow\4loop\3abc\4sink\4fuse"
93 
94 /* Optimization levels set a fixed combination of flags. */
95 #define JIT_F_OPT_0	0
96 #define JIT_F_OPT_1	(JIT_F_OPT_FOLD|JIT_F_OPT_CSE|JIT_F_OPT_DCE)
97 #define JIT_F_OPT_2	(JIT_F_OPT_1|JIT_F_OPT_NARROW|JIT_F_OPT_LOOP)
98 #define JIT_F_OPT_3	(JIT_F_OPT_2|\
99   JIT_F_OPT_FWD|JIT_F_OPT_DSE|JIT_F_OPT_ABC|JIT_F_OPT_SINK|JIT_F_OPT_FUSE)
100 #define JIT_F_OPT_DEFAULT	JIT_F_OPT_3
101 
102 /* -- JIT engine parameters ----------------------------------------------- */
103 
104 #if LJ_TARGET_WINDOWS || LJ_64
105 /* See: http://blogs.msdn.com/oldnewthing/archive/2003/10/08/55239.aspx */
106 #define JIT_P_sizemcode_DEFAULT		64
107 #else
108 /* Could go as low as 4K, but the mmap() overhead would be rather high. */
109 #define JIT_P_sizemcode_DEFAULT		32
110 #endif
111 
112 /* Optimization parameters and their defaults. Length is a char in octal! */
113 #define JIT_PARAMDEF(_) \
114   _(\010, maxtrace,	1000)	/* Max. # of traces in cache. */ \
115   _(\011, maxrecord,	4000)	/* Max. # of recorded IR instructions. */ \
116   _(\012, maxirconst,	500)	/* Max. # of IR constants of a trace. */ \
117   _(\007, maxside,	100)	/* Max. # of side traces of a root trace. */ \
118   _(\007, maxsnap,	500)	/* Max. # of snapshots for a trace. */ \
119   _(\011, minstitch,	0)	/* Min. # of IR ins for a stitched trace. */ \
120   \
121   _(\007, hotloop,	56)	/* # of iter. to detect a hot loop/call. */ \
122   _(\007, hotexit,	10)	/* # of taken exits to start a side trace. */ \
123   _(\007, tryside,	4)	/* # of attempts to compile a side trace. */ \
124   \
125   _(\012, instunroll,	4)	/* Max. unroll for instable loops. */ \
126   _(\012, loopunroll,	15)	/* Max. unroll for loop ops in side traces. */ \
127   _(\012, callunroll,	3)	/* Max. unroll for recursive calls. */ \
128   _(\011, recunroll,	2)	/* Min. unroll for true recursion. */ \
129   \
130   /* Size of each machine code area (in KBytes). */ \
131   _(\011, sizemcode,	JIT_P_sizemcode_DEFAULT) \
132   /* Max. total size of all machine code areas (in KBytes). */ \
133   _(\010, maxmcode,	512) \
134   /* End of list. */
135 
136 enum {
137 #define JIT_PARAMENUM(len, name, value)	JIT_P_##name,
138 JIT_PARAMDEF(JIT_PARAMENUM)
139 #undef JIT_PARAMENUM
140   JIT_P__MAX
141 };
142 
143 #define JIT_PARAMSTR(len, name, value)	#len #name
144 #define JIT_P_STRING	JIT_PARAMDEF(JIT_PARAMSTR)
145 
146 /* -- JIT engine data structures ------------------------------------------ */
147 
148 /* Trace compiler state. */
149 typedef enum {
150   LJ_TRACE_IDLE,	/* Trace compiler idle. */
151   LJ_TRACE_ACTIVE = 0x10,
152   LJ_TRACE_RECORD,	/* Bytecode recording active. */
153   LJ_TRACE_RECORD_1ST,	/* Record 1st instruction, too. */
154   LJ_TRACE_START,	/* New trace started. */
155   LJ_TRACE_END,		/* End of trace. */
156   LJ_TRACE_ASM,		/* Assemble trace. */
157   LJ_TRACE_ERR		/* Trace aborted with error. */
158 } TraceState;
159 
160 /* Post-processing action. */
161 typedef enum {
162   LJ_POST_NONE,		/* No action. */
163   LJ_POST_FIXCOMP,	/* Fixup comparison and emit pending guard. */
164   LJ_POST_FIXGUARD,	/* Fixup and emit pending guard. */
165   LJ_POST_FIXGUARDSNAP,	/* Fixup and emit pending guard and snapshot. */
166   LJ_POST_FIXBOOL,	/* Fixup boolean result. */
167   LJ_POST_FIXCONST,	/* Fixup constant results. */
168   LJ_POST_FFRETRY	/* Suppress recording of retried fast functions. */
169 } PostProc;
170 
171 /* Machine code type. */
172 #if LJ_TARGET_X86ORX64
173 typedef uint8_t MCode;
174 #else
175 typedef uint32_t MCode;
176 #endif
177 
178 /* Linked list of MCode areas. */
179 typedef struct MCLink {
180   MCode *next;		/* Next area. */
181   size_t size;		/* Size of current area. */
182 } MCLink;
183 
184 /* Stack snapshot header. */
185 typedef struct SnapShot {
186   uint32_t mapofs;	/* Offset into snapshot map. */
187   IRRef1 ref;		/* First IR ref for this snapshot. */
188   uint16_t mcofs;	/* Offset into machine code in MCode units. */
189   uint8_t nslots;	/* Number of valid slots. */
190   uint8_t topslot;	/* Maximum frame extent. */
191   uint8_t nent;		/* Number of compressed entries. */
192   uint8_t count;	/* Count of taken exits for this snapshot. */
193 } SnapShot;
194 
195 #define SNAPCOUNT_DONE	255	/* Already compiled and linked a side trace. */
196 
197 /* Compressed snapshot entry. */
198 typedef uint32_t SnapEntry;
199 
200 #define SNAP_FRAME		0x010000	/* Frame slot. */
201 #define SNAP_CONT		0x020000	/* Continuation slot. */
202 #define SNAP_NORESTORE		0x040000	/* No need to restore slot. */
203 #define SNAP_SOFTFPNUM		0x080000	/* Soft-float number. */
204 #define SNAP_KEYINDEX		0x100000	/* Traversal key index. */
205 LJ_STATIC_ASSERT(SNAP_FRAME == TREF_FRAME);
206 LJ_STATIC_ASSERT(SNAP_CONT == TREF_CONT);
207 LJ_STATIC_ASSERT(SNAP_KEYINDEX == TREF_KEYINDEX);
208 
209 #define SNAP(slot, flags, ref)	(((SnapEntry)(slot) << 24) + (flags) + (ref))
210 #define SNAP_TR(slot, tr) \
211   (((SnapEntry)(slot) << 24) + \
212    ((tr) & (TREF_KEYINDEX|TREF_CONT|TREF_FRAME|TREF_REFMASK)))
213 #if !LJ_FR2
214 #define SNAP_MKPC(pc)		((SnapEntry)u32ptr(pc))
215 #endif
216 #define SNAP_MKFTSZ(ftsz)	((SnapEntry)(ftsz))
217 #define snap_ref(sn)		((sn) & 0xffff)
218 #define snap_slot(sn)		((BCReg)((sn) >> 24))
219 #define snap_isframe(sn)	((sn) & SNAP_FRAME)
220 #define snap_setref(sn, ref)	(((sn) & (0xffff0000&~SNAP_NORESTORE)) | (ref))
221 
snap_pc(SnapEntry * sn)222 static LJ_AINLINE const BCIns *snap_pc(SnapEntry *sn)
223 {
224 #if LJ_FR2
225   uint64_t pcbase;
226   memcpy(&pcbase, sn, sizeof(uint64_t));
227   return (const BCIns *)(pcbase >> 8);
228 #else
229   return (const BCIns *)(uintptr_t)*sn;
230 #endif
231 }
232 
233 /* Snapshot and exit numbers. */
234 typedef uint32_t SnapNo;
235 typedef uint32_t ExitNo;
236 
237 /* Trace number. */
238 typedef uint32_t TraceNo;	/* Used to pass around trace numbers. */
239 typedef uint16_t TraceNo1;	/* Stored trace number. */
240 
241 /* Type of link. ORDER LJ_TRLINK */
242 typedef enum {
243   LJ_TRLINK_NONE,		/* Incomplete trace. No link, yet. */
244   LJ_TRLINK_ROOT,		/* Link to other root trace. */
245   LJ_TRLINK_LOOP,		/* Loop to same trace. */
246   LJ_TRLINK_TAILREC,		/* Tail-recursion. */
247   LJ_TRLINK_UPREC,		/* Up-recursion. */
248   LJ_TRLINK_DOWNREC,		/* Down-recursion. */
249   LJ_TRLINK_INTERP,		/* Fallback to interpreter. */
250   LJ_TRLINK_RETURN,		/* Return to interpreter. */
251   LJ_TRLINK_STITCH		/* Trace stitching. */
252 } TraceLink;
253 
254 /* Trace object. */
255 typedef struct GCtrace {
256   GCHeader;
257   uint16_t nsnap;	/* Number of snapshots. */
258   IRRef nins;		/* Next IR instruction. Biased with REF_BIAS. */
259 #if LJ_GC64
260   uint32_t unused_gc64;
261 #endif
262   GCRef gclist;
263   IRIns *ir;		/* IR instructions/constants. Biased with REF_BIAS. */
264   IRRef nk;		/* Lowest IR constant. Biased with REF_BIAS. */
265   uint32_t nsnapmap;	/* Number of snapshot map elements. */
266   SnapShot *snap;	/* Snapshot array. */
267   SnapEntry *snapmap;	/* Snapshot map. */
268   GCRef startpt;	/* Starting prototype. */
269   MRef startpc;		/* Bytecode PC of starting instruction. */
270   BCIns startins;	/* Original bytecode of starting instruction. */
271   MSize szmcode;	/* Size of machine code. */
272   MCode *mcode;		/* Start of machine code. */
273   MSize mcloop;		/* Offset of loop start in machine code. */
274   uint16_t nchild;	/* Number of child traces (root trace only). */
275   uint16_t spadjust;	/* Stack pointer adjustment (offset in bytes). */
276   TraceNo1 traceno;	/* Trace number. */
277   TraceNo1 link;	/* Linked trace (or self for loops). */
278   TraceNo1 root;	/* Root trace of side trace (or 0 for root traces). */
279   TraceNo1 nextroot;	/* Next root trace for same prototype. */
280   TraceNo1 nextside;	/* Next side trace of same root trace. */
281   uint8_t sinktags;	/* Trace has SINK tags. */
282   uint8_t topslot;	/* Top stack slot already checked to be allocated. */
283   uint8_t linktype;	/* Type of link. */
284   uint8_t unused1;
285 #ifdef LUAJIT_USE_GDBJIT
286   void *gdbjit_entry;	/* GDB JIT entry. */
287 #endif
288 } GCtrace;
289 
290 #define gco2trace(o)	check_exp((o)->gch.gct == ~LJ_TTRACE, (GCtrace *)(o))
291 #define traceref(J, n) \
292   check_exp((n)>0 && (MSize)(n)<J->sizetrace, (GCtrace *)gcref(J->trace[(n)]))
293 
294 LJ_STATIC_ASSERT(offsetof(GChead, gclist) == offsetof(GCtrace, gclist));
295 
snap_nextofs(GCtrace * T,SnapShot * snap)296 static LJ_AINLINE MSize snap_nextofs(GCtrace *T, SnapShot *snap)
297 {
298   if (snap+1 == &T->snap[T->nsnap])
299     return T->nsnapmap;
300   else
301     return (snap+1)->mapofs;
302 }
303 
304 /* Round-robin penalty cache for bytecodes leading to aborted traces. */
305 typedef struct HotPenalty {
306   MRef pc;		/* Starting bytecode PC. */
307   uint16_t val;		/* Penalty value, i.e. hotcount start. */
308   uint16_t reason;	/* Abort reason (really TraceErr). */
309 } HotPenalty;
310 
311 #define PENALTY_SLOTS	64	/* Penalty cache slot. Must be a power of 2. */
312 #define PENALTY_MIN	(36*2)	/* Minimum penalty value. */
313 #define PENALTY_MAX	60000	/* Maximum penalty value. */
314 #define PENALTY_RNDBITS	4	/* # of random bits to add to penalty value. */
315 
316 /* Round-robin backpropagation cache for narrowing conversions. */
317 typedef struct BPropEntry {
318   IRRef1 key;		/* Key: original reference. */
319   IRRef1 val;		/* Value: reference after conversion. */
320   IRRef mode;		/* Mode for this entry (currently IRCONV_*). */
321 } BPropEntry;
322 
323 /* Number of slots for the backpropagation cache. Must be a power of 2. */
324 #define BPROP_SLOTS	16
325 
326 /* Scalar evolution analysis cache. */
327 typedef struct ScEvEntry {
328   MRef pc;		/* Bytecode PC of FORI. */
329   IRRef1 idx;		/* Index reference. */
330   IRRef1 start;		/* Constant start reference. */
331   IRRef1 stop;		/* Constant stop reference. */
332   IRRef1 step;		/* Constant step reference. */
333   IRType1 t;		/* Scalar type. */
334   uint8_t dir;		/* Direction. 1: +, 0: -. */
335 } ScEvEntry;
336 
337 /* Reverse bytecode map (IRRef -> PC). Only for selected instructions. */
338 typedef struct RBCHashEntry {
339   MRef pc;		/* Bytecode PC. */
340   GCRef pt;		/* Prototype. */
341   IRRef ref;		/* IR reference. */
342 } RBCHashEntry;
343 
344 /* Number of slots in the reverse bytecode hash table. Must be a power of 2. */
345 #define RBCHASH_SLOTS	8
346 
347 /* 128 bit SIMD constants. */
348 enum {
349   LJ_KSIMD_ABS,
350   LJ_KSIMD_NEG,
351   LJ_KSIMD__MAX
352 };
353 
354 enum {
355 #if LJ_TARGET_X86ORX64
356   LJ_K64_TOBIT,		/* 2^52 + 2^51 */
357   LJ_K64_2P64,		/* 2^64 */
358   LJ_K64_M2P64,		/* -2^64 */
359 #if LJ_32
360   LJ_K64_M2P64_31,	/* -2^64 or -2^31 */
361 #else
362   LJ_K64_M2P64_31 = LJ_K64_M2P64,
363 #endif
364 #endif
365 #if LJ_TARGET_MIPS
366   LJ_K64_2P31,		/* 2^31 */
367 #if LJ_64
368   LJ_K64_2P63,		/* 2^63 */
369   LJ_K64_M2P64,		/* -2^64 */
370 #endif
371 #endif
372   LJ_K64__MAX,
373 };
374 
375 enum {
376 #if LJ_TARGET_X86ORX64
377   LJ_K32_M2P64_31,	/* -2^64 or -2^31 */
378 #endif
379 #if LJ_TARGET_PPC
380   LJ_K32_2P52_2P31,	/* 2^52 + 2^31 */
381   LJ_K32_2P52,		/* 2^52 */
382 #endif
383 #if LJ_TARGET_PPC || LJ_TARGET_MIPS
384   LJ_K32_2P31,		/* 2^31 */
385 #endif
386 #if LJ_TARGET_MIPS64
387   LJ_K32_2P63,		/* 2^63 */
388   LJ_K32_M2P64,		/* -2^64 */
389 #endif
390   LJ_K32__MAX
391 };
392 
393 /* Get 16 byte aligned pointer to SIMD constant. */
394 #define LJ_KSIMD(J, n) \
395   ((TValue *)(((intptr_t)&J->ksimd[2*(n)] + 15) & ~(intptr_t)15))
396 
397 /* Set/reset flag to activate the SPLIT pass for the current trace. */
398 #if LJ_SOFTFP32 || (LJ_32 && LJ_HASFFI)
399 #define lj_needsplit(J)		(J->needsplit = 1)
400 #define lj_resetsplit(J)	(J->needsplit = 0)
401 #else
402 #define lj_needsplit(J)		UNUSED(J)
403 #define lj_resetsplit(J)	UNUSED(J)
404 #endif
405 
406 /* Fold state is used to fold instructions on-the-fly. */
407 typedef struct FoldState {
408   IRIns ins;		/* Currently emitted instruction. */
409   IRIns left[2];	/* Instruction referenced by left operand. */
410   IRIns right[2];	/* Instruction referenced by right operand. */
411 } FoldState;
412 
413 /* JIT compiler state. */
414 typedef struct jit_State {
415   GCtrace cur;		/* Current trace. */
416   GCtrace *curfinal;	/* Final address of current trace (set during asm). */
417 
418   lua_State *L;		/* Current Lua state. */
419   const BCIns *pc;	/* Current PC. */
420   GCfunc *fn;		/* Current function. */
421   GCproto *pt;		/* Current prototype. */
422   TRef *base;		/* Current frame base, points into J->slots. */
423 
424   uint32_t flags;	/* JIT engine flags. */
425   BCReg maxslot;	/* Relative to baseslot. */
426   BCReg baseslot;	/* Current frame base, offset into J->slots. */
427 
428   uint8_t mergesnap;	/* Allowed to merge with next snapshot. */
429   uint8_t needsnap;	/* Need snapshot before recording next bytecode. */
430   IRType1 guardemit;	/* Accumulated IRT_GUARD for emitted instructions. */
431   uint8_t bcskip;	/* Number of bytecode instructions to skip. */
432 
433   FoldState fold;	/* Fold state. */
434 
435   const BCIns *bc_min;	/* Start of allowed bytecode range for root trace. */
436   MSize bc_extent;	/* Extent of the range. */
437 
438   TraceState state;	/* Trace compiler state. */
439 
440   int32_t instunroll;	/* Unroll counter for instable loops. */
441   int32_t loopunroll;	/* Unroll counter for loop ops in side traces. */
442   int32_t tailcalled;	/* Number of successive tailcalls. */
443   int32_t framedepth;	/* Current frame depth. */
444   int32_t retdepth;	/* Return frame depth (count of RETF). */
445 
446   uint32_t k32[LJ_K32__MAX];  /* Common 4 byte constants used by backends. */
447   TValue ksimd[LJ_KSIMD__MAX*2+1];  /* 16 byte aligned SIMD constants. */
448   TValue k64[LJ_K64__MAX];  /* Common 8 byte constants. */
449 
450   IRIns *irbuf;		/* Temp. IR instruction buffer. Biased with REF_BIAS. */
451   IRRef irtoplim;	/* Upper limit of instuction buffer (biased). */
452   IRRef irbotlim;	/* Lower limit of instuction buffer (biased). */
453   IRRef loopref;	/* Last loop reference or ref of final LOOP (or 0). */
454 
455   MSize sizesnap;	/* Size of temp. snapshot buffer. */
456   SnapShot *snapbuf;	/* Temp. snapshot buffer. */
457   SnapEntry *snapmapbuf;  /* Temp. snapshot map buffer. */
458   MSize sizesnapmap;	/* Size of temp. snapshot map buffer. */
459 
460   PostProc postproc;	/* Required post-processing after execution. */
461 #if LJ_SOFTFP32 || (LJ_32 && LJ_HASFFI)
462   uint8_t needsplit;	/* Need SPLIT pass. */
463 #endif
464   uint8_t retryrec;	/* Retry recording. */
465 
466   GCRef *trace;		/* Array of traces. */
467   TraceNo freetrace;	/* Start of scan for next free trace. */
468   MSize sizetrace;	/* Size of trace array. */
469   IRRef1 ktrace;	/* Reference to KGC with GCtrace. */
470 
471   IRRef1 chain[IR__MAX];  /* IR instruction skip-list chain anchors. */
472   TRef slot[LJ_MAX_JSLOTS+LJ_STACK_EXTRA];  /* Stack slot map. */
473 
474   int32_t param[JIT_P__MAX];  /* JIT engine parameters. */
475 
476   MCode *exitstubgroup[LJ_MAX_EXITSTUBGR];  /* Exit stub group addresses. */
477 
478   HotPenalty penalty[PENALTY_SLOTS];  /* Penalty slots. */
479   uint32_t penaltyslot;	/* Round-robin index into penalty slots. */
480 
481 #ifdef LUAJIT_ENABLE_TABLE_BUMP
482   RBCHashEntry rbchash[RBCHASH_SLOTS];  /* Reverse bytecode map. */
483 #endif
484 
485   BPropEntry bpropcache[BPROP_SLOTS];  /* Backpropagation cache slots. */
486   uint32_t bpropslot;	/* Round-robin index into bpropcache slots. */
487 
488   ScEvEntry scev;	/* Scalar evolution analysis cache slots. */
489 
490   const BCIns *startpc;	/* Bytecode PC of starting instruction. */
491   TraceNo parent;	/* Parent of current side trace (0 for root traces). */
492   ExitNo exitno;	/* Exit number in parent of current side trace. */
493   int exitcode;		/* Exit code from unwound trace. */
494 
495   BCIns *patchpc;	/* PC for pending re-patch. */
496   BCIns patchins;	/* Instruction for pending re-patch. */
497 
498   int mcprot;		/* Protection of current mcode area. */
499   MCode *mcarea;	/* Base of current mcode area. */
500   MCode *mctop;		/* Top of current mcode area. */
501   MCode *mcbot;		/* Bottom of current mcode area. */
502   size_t szmcarea;	/* Size of current mcode area. */
503   size_t szallmcarea;	/* Total size of all allocated mcode areas. */
504 
505   TValue errinfo;	/* Additional info element for trace errors. */
506 
507 #if LJ_HASPROFILE
508   GCproto *prev_pt;	/* Previous prototype. */
509   BCLine prev_line;	/* Previous line. */
510   int prof_mode;	/* Profiling mode: 0, 'f', 'l'. */
511 #endif
512 } jit_State;
513 
514 #ifdef LUA_USE_ASSERT
515 #define lj_assertJ(c, ...)	lj_assertG_(J2G(J), (c), __VA_ARGS__)
516 #else
517 #define lj_assertJ(c, ...)	((void)J)
518 #endif
519 
520 #endif
521