1 /*
2 ** $Id: lcode.c,v 2.112.1.1 2017/04/19 17:20:42 roberto Exp $
3 ** Code generator for Lua
4 ** See Copyright Notice in lua.h
5 */
6 
7 #define lcode_c
8 #define LUA_CORE
9 
10 #include "lprefix.h"
11 
12 
13 #include <math.h>
14 #include <stdlib.h>
15 
16 #include "lua.h"
17 
18 #include "lcode.h"
19 #include "ldebug.h"
20 #include "ldo.h"
21 #include "lgc.h"
22 #include "llex.h"
23 #include "lmem.h"
24 #include "lobject.h"
25 #include "lopcodes.h"
26 #include "lparser.h"
27 #include "lstring.h"
28 #include "ltable.h"
29 #include "lvm.h"
30 
31 
32 /* Maximum number of registers in a Lua function (must fit in 8 bits) */
33 #define MAXREGS		255
34 
35 
36 #define hasjumps(e)	((e)->t != (e)->f)
37 
38 
39 /*
40 ** If expression is a numeric constant, fills 'v' with its value
41 ** and returns 1. Otherwise, returns 0.
42 */
tonumeral(const expdesc * e,TValue * v)43 static int tonumeral(const expdesc *e, TValue *v) {
44   if (hasjumps(e))
45     return 0;  /* not a numeral */
46   switch (e->k) {
47     case VKINT:
48       if (v) setivalue(v, e->u.ival);
49       return 1;
50     case VKFLT:
51       if (v) setfltvalue(v, e->u.nval);
52       return 1;
53     default: return 0;
54   }
55 }
56 
57 
58 /*
59 ** Create a OP_LOADNIL instruction, but try to optimize: if the previous
60 ** instruction is also OP_LOADNIL and ranges are compatible, adjust
61 ** range of previous instruction instead of emitting a new one. (For
62 ** instance, 'local a; local b' will generate a single opcode.)
63 */
luaK_nil(FuncState * fs,int from,int n)64 void luaK_nil (FuncState *fs, int from, int n) {
65   Instruction *previous;
66   int l = from + n - 1;  /* last register to set nil */
67   if (fs->pc > fs->lasttarget) {  /* no jumps to current position? */
68     previous = &fs->f->code[fs->pc-1];
69     if (GET_OPCODE(*previous) == OP_LOADNIL) {  /* previous is LOADNIL? */
70       int pfrom = GETARG_A(*previous);  /* get previous range */
71       int pl = pfrom + GETARG_B(*previous);
72       if ((pfrom <= from && from <= pl + 1) ||
73           (from <= pfrom && pfrom <= l + 1)) {  /* can connect both? */
74         if (pfrom < from) from = pfrom;  /* from = min(from, pfrom) */
75         if (pl > l) l = pl;  /* l = max(l, pl) */
76         SETARG_A(*previous, from);
77         SETARG_B(*previous, l - from);
78         return;
79       }
80     }  /* else go through */
81   }
82   luaK_codeABC(fs, OP_LOADNIL, from, n - 1, 0);  /* else no optimization */
83 }
84 
85 
86 /*
87 ** Gets the destination address of a jump instruction. Used to traverse
88 ** a list of jumps.
89 */
getjump(FuncState * fs,int pc)90 static int getjump (FuncState *fs, int pc) {
91   int offset = GETARG_sBx(fs->f->code[pc]);
92   if (offset == NO_JUMP)  /* point to itself represents end of list */
93     return NO_JUMP;  /* end of list */
94   else
95     return (pc+1)+offset;  /* turn offset into absolute position */
96 }
97 
98 
99 /*
100 ** Fix jump instruction at position 'pc' to jump to 'dest'.
101 ** (Jump addresses are relative in Lua)
102 */
fixjump(FuncState * fs,int pc,int dest)103 static void fixjump (FuncState *fs, int pc, int dest) {
104   Instruction *jmp = &fs->f->code[pc];
105   int offset = dest - (pc + 1);
106   lua_assert(dest != NO_JUMP);
107   if (abs(offset) > MAXARG_sBx)
108     luaX_syntaxerror(fs->ls, "control structure too long");
109   SETARG_sBx(*jmp, offset);
110 }
111 
112 
113 /*
114 ** Concatenate jump-list 'l2' into jump-list 'l1'
115 */
luaK_concat(FuncState * fs,int * l1,int l2)116 void luaK_concat (FuncState *fs, int *l1, int l2) {
117   if (l2 == NO_JUMP) return;  /* nothing to concatenate? */
118   else if (*l1 == NO_JUMP)  /* no original list? */
119     *l1 = l2;  /* 'l1' points to 'l2' */
120   else {
121     int list = *l1;
122     int next;
123     while ((next = getjump(fs, list)) != NO_JUMP)  /* find last element */
124       list = next;
125     fixjump(fs, list, l2);  /* last element links to 'l2' */
126   }
127 }
128 
129 
130 /*
131 ** Create a jump instruction and return its position, so its destination
132 ** can be fixed later (with 'fixjump'). If there are jumps to
133 ** this position (kept in 'jpc'), link them all together so that
134 ** 'patchlistaux' will fix all them directly to the final destination.
135 */
luaK_jump(FuncState * fs)136 int luaK_jump (FuncState *fs) {
137   int jpc = fs->jpc;  /* save list of jumps to here */
138   int j;
139   fs->jpc = NO_JUMP;  /* no more jumps to here */
140   j = luaK_codeAsBx(fs, OP_JMP, 0, NO_JUMP);
141   luaK_concat(fs, &j, jpc);  /* keep them on hold */
142   return j;
143 }
144 
145 
146 /*
147 ** Code a 'return' instruction
148 */
luaK_ret(FuncState * fs,int first,int nret)149 void luaK_ret (FuncState *fs, int first, int nret) {
150   luaK_codeABC(fs, OP_RETURN, first, nret+1, 0);
151 }
152 
153 
154 /*
155 ** Code a "conditional jump", that is, a test or comparison opcode
156 ** followed by a jump. Return jump position.
157 */
condjump(FuncState * fs,OpCode op,int A,int B,int C)158 static int condjump (FuncState *fs, OpCode op, int A, int B, int C) {
159   luaK_codeABC(fs, op, A, B, C);
160   return luaK_jump(fs);
161 }
162 
163 
164 /*
165 ** returns current 'pc' and marks it as a jump target (to avoid wrong
166 ** optimizations with consecutive instructions not in the same basic block).
167 */
luaK_getlabel(FuncState * fs)168 int luaK_getlabel (FuncState *fs) {
169   fs->lasttarget = fs->pc;
170   return fs->pc;
171 }
172 
173 
174 /*
175 ** Returns the position of the instruction "controlling" a given
176 ** jump (that is, its condition), or the jump itself if it is
177 ** unconditional.
178 */
getjumpcontrol(FuncState * fs,int pc)179 static Instruction *getjumpcontrol (FuncState *fs, int pc) {
180   Instruction *pi = &fs->f->code[pc];
181   if (pc >= 1 && testTMode(GET_OPCODE(*(pi-1))))
182     return pi-1;
183   else
184     return pi;
185 }
186 
187 
188 /*
189 ** Patch destination register for a TESTSET instruction.
190 ** If instruction in position 'node' is not a TESTSET, return 0 ("fails").
191 ** Otherwise, if 'reg' is not 'NO_REG', set it as the destination
192 ** register. Otherwise, change instruction to a simple 'TEST' (produces
193 ** no register value)
194 */
patchtestreg(FuncState * fs,int node,int reg)195 static int patchtestreg (FuncState *fs, int node, int reg) {
196   Instruction *i = getjumpcontrol(fs, node);
197   if (GET_OPCODE(*i) != OP_TESTSET)
198     return 0;  /* cannot patch other instructions */
199   if (reg != NO_REG && reg != GETARG_B(*i))
200     SETARG_A(*i, reg);
201   else {
202      /* no register to put value or register already has the value;
203         change instruction to simple test */
204     *i = CREATE_ABC(OP_TEST, GETARG_B(*i), 0, GETARG_C(*i));
205   }
206   return 1;
207 }
208 
209 
210 /*
211 ** Traverse a list of tests ensuring no one produces a value
212 */
removevalues(FuncState * fs,int list)213 static void removevalues (FuncState *fs, int list) {
214   for (; list != NO_JUMP; list = getjump(fs, list))
215       patchtestreg(fs, list, NO_REG);
216 }
217 
218 
219 /*
220 ** Traverse a list of tests, patching their destination address and
221 ** registers: tests producing values jump to 'vtarget' (and put their
222 ** values in 'reg'), other tests jump to 'dtarget'.
223 */
patchlistaux(FuncState * fs,int list,int vtarget,int reg,int dtarget)224 static void patchlistaux (FuncState *fs, int list, int vtarget, int reg,
225                           int dtarget) {
226   while (list != NO_JUMP) {
227     int next = getjump(fs, list);
228     if (patchtestreg(fs, list, reg))
229       fixjump(fs, list, vtarget);
230     else
231       fixjump(fs, list, dtarget);  /* jump to default target */
232     list = next;
233   }
234 }
235 
236 
237 /*
238 ** Ensure all pending jumps to current position are fixed (jumping
239 ** to current position with no values) and reset list of pending
240 ** jumps
241 */
dischargejpc(FuncState * fs)242 static void dischargejpc (FuncState *fs) {
243   patchlistaux(fs, fs->jpc, fs->pc, NO_REG, fs->pc);
244   fs->jpc = NO_JUMP;
245 }
246 
247 
248 /*
249 ** Add elements in 'list' to list of pending jumps to "here"
250 ** (current position)
251 */
luaK_patchtohere(FuncState * fs,int list)252 void luaK_patchtohere (FuncState *fs, int list) {
253   luaK_getlabel(fs);  /* mark "here" as a jump target */
254   luaK_concat(fs, &fs->jpc, list);
255 }
256 
257 
258 /*
259 ** Path all jumps in 'list' to jump to 'target'.
260 ** (The assert means that we cannot fix a jump to a forward address
261 ** because we only know addresses once code is generated.)
262 */
luaK_patchlist(FuncState * fs,int list,int target)263 void luaK_patchlist (FuncState *fs, int list, int target) {
264   if (target == fs->pc)  /* 'target' is current position? */
265     luaK_patchtohere(fs, list);  /* add list to pending jumps */
266   else {
267     lua_assert(target < fs->pc);
268     patchlistaux(fs, list, target, NO_REG, target);
269   }
270 }
271 
272 
273 /*
274 ** Path all jumps in 'list' to close upvalues up to given 'level'
275 ** (The assertion checks that jumps either were closing nothing
276 ** or were closing higher levels, from inner blocks.)
277 */
luaK_patchclose(FuncState * fs,int list,int level)278 void luaK_patchclose (FuncState *fs, int list, int level) {
279   level++;  /* argument is +1 to reserve 0 as non-op */
280   for (; list != NO_JUMP; list = getjump(fs, list)) {
281     lua_assert(GET_OPCODE(fs->f->code[list]) == OP_JMP &&
282                 (GETARG_A(fs->f->code[list]) == 0 ||
283                  GETARG_A(fs->f->code[list]) >= level));
284     SETARG_A(fs->f->code[list], level);
285   }
286 }
287 
288 
289 /*
290 ** Emit instruction 'i', checking for array sizes and saving also its
291 ** line information. Return 'i' position.
292 */
luaK_code(FuncState * fs,Instruction i)293 static int luaK_code (FuncState *fs, Instruction i) {
294   Proto *f = fs->f;
295   dischargejpc(fs);  /* 'pc' will change */
296   /* put new instruction in code array */
297   luaM_growvector(fs->ls->L, f->code, fs->pc, f->sizecode, Instruction,
298                   MAX_INT, "opcodes");
299   f->code[fs->pc] = i;
300   /* save corresponding line information */
301   luaM_growvector(fs->ls->L, f->lineinfo, fs->pc, f->sizelineinfo, int,
302                   MAX_INT, "opcodes");
303   f->lineinfo[fs->pc] = fs->ls->lastline;
304   return fs->pc++;
305 }
306 
307 
308 /*
309 ** Format and emit an 'iABC' instruction. (Assertions check consistency
310 ** of parameters versus opcode.)
311 */
luaK_codeABC(FuncState * fs,OpCode o,int a,int b,int c)312 int luaK_codeABC (FuncState *fs, OpCode o, int a, int b, int c) {
313   lua_assert(getOpMode(o) == iABC);
314   lua_assert(getBMode(o) != OpArgN || b == 0);
315   lua_assert(getCMode(o) != OpArgN || c == 0);
316   lua_assert(a <= MAXARG_A && b <= MAXARG_B && c <= MAXARG_C);
317   return luaK_code(fs, CREATE_ABC(o, a, b, c));
318 }
319 
320 
321 /*
322 ** Format and emit an 'iABx' instruction.
323 */
luaK_codeABx(FuncState * fs,OpCode o,int a,unsigned int bc)324 int luaK_codeABx (FuncState *fs, OpCode o, int a, unsigned int bc) {
325   lua_assert(getOpMode(o) == iABx || getOpMode(o) == iAsBx);
326   lua_assert(getCMode(o) == OpArgN);
327   lua_assert(a <= MAXARG_A && bc <= MAXARG_Bx);
328   return luaK_code(fs, CREATE_ABx(o, a, bc));
329 }
330 
331 
332 /*
333 ** Emit an "extra argument" instruction (format 'iAx')
334 */
codeextraarg(FuncState * fs,int a)335 static int codeextraarg (FuncState *fs, int a) {
336   lua_assert(a <= MAXARG_Ax);
337   return luaK_code(fs, CREATE_Ax(OP_EXTRAARG, a));
338 }
339 
340 
341 /*
342 ** Emit a "load constant" instruction, using either 'OP_LOADK'
343 ** (if constant index 'k' fits in 18 bits) or an 'OP_LOADKX'
344 ** instruction with "extra argument".
345 */
luaK_codek(FuncState * fs,int reg,int k)346 int luaK_codek (FuncState *fs, int reg, int k) {
347   if (k <= MAXARG_Bx)
348     return luaK_codeABx(fs, OP_LOADK, reg, k);
349   else {
350     int p = luaK_codeABx(fs, OP_LOADKX, reg, 0);
351     codeextraarg(fs, k);
352     return p;
353   }
354 }
355 
356 
357 /*
358 ** Check register-stack level, keeping track of its maximum size
359 ** in field 'maxstacksize'
360 */
luaK_checkstack(FuncState * fs,int n)361 void luaK_checkstack (FuncState *fs, int n) {
362   int newstack = fs->freereg + n;
363   if (newstack > fs->f->maxstacksize) {
364     if (newstack >= MAXREGS)
365       luaX_syntaxerror(fs->ls,
366         "function or expression needs too many registers");
367     fs->f->maxstacksize = cast_byte(newstack);
368   }
369 }
370 
371 
372 /*
373 ** Reserve 'n' registers in register stack
374 */
luaK_reserveregs(FuncState * fs,int n)375 void luaK_reserveregs (FuncState *fs, int n) {
376   luaK_checkstack(fs, n);
377   fs->freereg += n;
378 }
379 
380 
381 /*
382 ** Free register 'reg', if it is neither a constant index nor
383 ** a local variable.
384 )
385 */
freereg(FuncState * fs,int reg)386 static void freereg (FuncState *fs, int reg) {
387   if (!ISK(reg) && reg >= fs->nactvar) {
388     fs->freereg--;
389     lua_assert(reg == fs->freereg);
390   }
391 }
392 
393 
394 /*
395 ** Free register used by expression 'e' (if any)
396 */
freeexp(FuncState * fs,expdesc * e)397 static void freeexp (FuncState *fs, expdesc *e) {
398   if (e->k == VNONRELOC)
399     freereg(fs, e->u.info);
400 }
401 
402 
403 /*
404 ** Free registers used by expressions 'e1' and 'e2' (if any) in proper
405 ** order.
406 */
freeexps(FuncState * fs,expdesc * e1,expdesc * e2)407 static void freeexps (FuncState *fs, expdesc *e1, expdesc *e2) {
408   int r1 = (e1->k == VNONRELOC) ? e1->u.info : -1;
409   int r2 = (e2->k == VNONRELOC) ? e2->u.info : -1;
410   if (r1 > r2) {
411     freereg(fs, r1);
412     freereg(fs, r2);
413   }
414   else {
415     freereg(fs, r2);
416     freereg(fs, r1);
417   }
418 }
419 
420 
421 /*
422 ** Add constant 'v' to prototype's list of constants (field 'k').
423 ** Use scanner's table to cache position of constants in constant list
424 ** and try to reuse constants. Because some values should not be used
425 ** as keys (nil cannot be a key, integer keys can collapse with float
426 ** keys), the caller must provide a useful 'key' for indexing the cache.
427 */
addk(FuncState * fs,TValue * key,TValue * v)428 static int addk (FuncState *fs, TValue *key, TValue *v) {
429   lua_State *L = fs->ls->L;
430   Proto *f = fs->f;
431   TValue *idx = luaH_set(L, fs->ls->h, key);  /* index scanner table */
432   int k, oldsize;
433   if (ttisinteger(idx)) {  /* is there an index there? */
434     k = cast_int(ivalue(idx));
435     /* correct value? (warning: must distinguish floats from integers!) */
436     if (k < fs->nk && ttype(&f->k[k]) == ttype(v) &&
437                       luaV_rawequalobj(&f->k[k], v))
438       return k;  /* reuse index */
439   }
440   /* constant not found; create a new entry */
441   oldsize = f->sizek;
442   k = fs->nk;
443   /* numerical value does not need GC barrier;
444      table has no metatable, so it does not need to invalidate cache */
445   setivalue(idx, k);
446   luaM_growvector(L, f->k, k, f->sizek, TValue, MAXARG_Ax, "constants");
447   while (oldsize < f->sizek) setnilvalue(&f->k[oldsize++]);
448   setobj(L, &f->k[k], v);
449   fs->nk++;
450   luaC_barrier(L, f, v);
451   return k;
452 }
453 
454 
455 /*
456 ** Add a string to list of constants and return its index.
457 */
luaK_stringK(FuncState * fs,TString * s)458 int luaK_stringK (FuncState *fs, TString *s) {
459   TValue o;
460   setsvalue(fs->ls->L, &o, s);
461   return addk(fs, &o, &o);  /* use string itself as key */
462 }
463 
464 
465 /*
466 ** Add an integer to list of constants and return its index.
467 ** Integers use userdata as keys to avoid collision with floats with
468 ** same value; conversion to 'void*' is used only for hashing, so there
469 ** are no "precision" problems.
470 */
luaK_intK(FuncState * fs,lua_Integer n)471 int luaK_intK (FuncState *fs, lua_Integer n) {
472   TValue k, o;
473   setpvalue(&k, cast(void*, cast(size_t, n)));
474   setivalue(&o, n);
475   return addk(fs, &k, &o);
476 }
477 
478 /*
479 ** Add a float to list of constants and return its index.
480 */
luaK_numberK(FuncState * fs,lua_Number r)481 static int luaK_numberK (FuncState *fs, lua_Number r) {
482   TValue o;
483   setfltvalue(&o, r);
484   return addk(fs, &o, &o);  /* use number itself as key */
485 }
486 
487 
488 /*
489 ** Add a boolean to list of constants and return its index.
490 */
boolK(FuncState * fs,int b)491 static int boolK (FuncState *fs, int b) {
492   TValue o;
493   setbvalue(&o, b);
494   return addk(fs, &o, &o);  /* use boolean itself as key */
495 }
496 
497 
498 /*
499 ** Add nil to list of constants and return its index.
500 */
nilK(FuncState * fs)501 static int nilK (FuncState *fs) {
502   TValue k, v;
503   setnilvalue(&v);
504   /* cannot use nil as key; instead use table itself to represent nil */
505   sethvalue(fs->ls->L, &k, fs->ls->h);
506   return addk(fs, &k, &v);
507 }
508 
509 
510 /*
511 ** Fix an expression to return the number of results 'nresults'.
512 ** Either 'e' is a multi-ret expression (function call or vararg)
513 ** or 'nresults' is LUA_MULTRET (as any expression can satisfy that).
514 */
luaK_setreturns(FuncState * fs,expdesc * e,int nresults)515 void luaK_setreturns (FuncState *fs, expdesc *e, int nresults) {
516   if (e->k == VCALL) {  /* expression is an open function call? */
517     SETARG_C(getinstruction(fs, e), nresults + 1);
518   }
519   else if (e->k == VVARARG) {
520     Instruction *pc = &getinstruction(fs, e);
521     SETARG_B(*pc, nresults + 1);
522     SETARG_A(*pc, fs->freereg);
523     luaK_reserveregs(fs, 1);
524   }
525   else lua_assert(nresults == LUA_MULTRET);
526 }
527 
528 
529 /*
530 ** Fix an expression to return one result.
531 ** If expression is not a multi-ret expression (function call or
532 ** vararg), it already returns one result, so nothing needs to be done.
533 ** Function calls become VNONRELOC expressions (as its result comes
534 ** fixed in the base register of the call), while vararg expressions
535 ** become VRELOCABLE (as OP_VARARG puts its results where it wants).
536 ** (Calls are created returning one result, so that does not need
537 ** to be fixed.)
538 */
luaK_setoneret(FuncState * fs,expdesc * e)539 void luaK_setoneret (FuncState *fs, expdesc *e) {
540   if (e->k == VCALL) {  /* expression is an open function call? */
541     /* already returns 1 value */
542     lua_assert(GETARG_C(getinstruction(fs, e)) == 2);
543     e->k = VNONRELOC;  /* result has fixed position */
544     e->u.info = GETARG_A(getinstruction(fs, e));
545   }
546   else if (e->k == VVARARG) {
547     SETARG_B(getinstruction(fs, e), 2);
548     e->k = VRELOCABLE;  /* can relocate its simple result */
549   }
550 }
551 
552 
553 /*
554 ** Ensure that expression 'e' is not a variable.
555 */
luaK_dischargevars(FuncState * fs,expdesc * e)556 void luaK_dischargevars (FuncState *fs, expdesc *e) {
557   switch (e->k) {
558     case VLOCAL: {  /* already in a register */
559       e->k = VNONRELOC;  /* becomes a non-relocatable value */
560       break;
561     }
562     case VUPVAL: {  /* move value to some (pending) register */
563       e->u.info = luaK_codeABC(fs, OP_GETUPVAL, 0, e->u.info, 0);
564       e->k = VRELOCABLE;
565       break;
566     }
567     case VINDEXED: {
568       OpCode op;
569       freereg(fs, e->u.ind.idx);
570       if (e->u.ind.vt == VLOCAL) {  /* is 't' in a register? */
571         freereg(fs, e->u.ind.t);
572         op = OP_GETTABLE;
573       }
574       else {
575         lua_assert(e->u.ind.vt == VUPVAL);
576         op = OP_GETTABUP;  /* 't' is in an upvalue */
577       }
578       e->u.info = luaK_codeABC(fs, op, 0, e->u.ind.t, e->u.ind.idx);
579       e->k = VRELOCABLE;
580       break;
581     }
582     case VVARARG: case VCALL: {
583       luaK_setoneret(fs, e);
584       break;
585     }
586     default: break;  /* there is one value available (somewhere) */
587   }
588 }
589 
590 
591 /*
592 ** Ensures expression value is in register 'reg' (and therefore
593 ** 'e' will become a non-relocatable expression).
594 */
discharge2reg(FuncState * fs,expdesc * e,int reg)595 static void discharge2reg (FuncState *fs, expdesc *e, int reg) {
596   luaK_dischargevars(fs, e);
597   switch (e->k) {
598     case VNIL: {
599       luaK_nil(fs, reg, 1);
600       break;
601     }
602     case VFALSE: case VTRUE: {
603       luaK_codeABC(fs, OP_LOADBOOL, reg, e->k == VTRUE, 0);
604       break;
605     }
606     case VK: {
607       luaK_codek(fs, reg, e->u.info);
608       break;
609     }
610     case VKFLT: {
611       luaK_codek(fs, reg, luaK_numberK(fs, e->u.nval));
612       break;
613     }
614     case VKINT: {
615       luaK_codek(fs, reg, luaK_intK(fs, e->u.ival));
616       break;
617     }
618     case VRELOCABLE: {
619       Instruction *pc = &getinstruction(fs, e);
620       SETARG_A(*pc, reg);  /* instruction will put result in 'reg' */
621       break;
622     }
623     case VNONRELOC: {
624       if (reg != e->u.info)
625         luaK_codeABC(fs, OP_MOVE, reg, e->u.info, 0);
626       break;
627     }
628     default: {
629       lua_assert(e->k == VJMP);
630       return;  /* nothing to do... */
631     }
632   }
633   e->u.info = reg;
634   e->k = VNONRELOC;
635 }
636 
637 
638 /*
639 ** Ensures expression value is in any register.
640 */
discharge2anyreg(FuncState * fs,expdesc * e)641 static void discharge2anyreg (FuncState *fs, expdesc *e) {
642   if (e->k != VNONRELOC) {  /* no fixed register yet? */
643     luaK_reserveregs(fs, 1);  /* get a register */
644     discharge2reg(fs, e, fs->freereg-1);  /* put value there */
645   }
646 }
647 
648 
code_loadbool(FuncState * fs,int A,int b,int jump)649 static int code_loadbool (FuncState *fs, int A, int b, int jump) {
650   luaK_getlabel(fs);  /* those instructions may be jump targets */
651   return luaK_codeABC(fs, OP_LOADBOOL, A, b, jump);
652 }
653 
654 
655 /*
656 ** check whether list has any jump that do not produce a value
657 ** or produce an inverted value
658 */
need_value(FuncState * fs,int list)659 static int need_value (FuncState *fs, int list) {
660   for (; list != NO_JUMP; list = getjump(fs, list)) {
661     Instruction i = *getjumpcontrol(fs, list);
662     if (GET_OPCODE(i) != OP_TESTSET) return 1;
663   }
664   return 0;  /* not found */
665 }
666 
667 
668 /*
669 ** Ensures final expression result (including results from its jump
670 ** lists) is in register 'reg'.
671 ** If expression has jumps, need to patch these jumps either to
672 ** its final position or to "load" instructions (for those tests
673 ** that do not produce values).
674 */
exp2reg(FuncState * fs,expdesc * e,int reg)675 static void exp2reg (FuncState *fs, expdesc *e, int reg) {
676   discharge2reg(fs, e, reg);
677   if (e->k == VJMP)  /* expression itself is a test? */
678     luaK_concat(fs, &e->t, e->u.info);  /* put this jump in 't' list */
679   if (hasjumps(e)) {
680     int final;  /* position after whole expression */
681     int p_f = NO_JUMP;  /* position of an eventual LOAD false */
682     int p_t = NO_JUMP;  /* position of an eventual LOAD true */
683     if (need_value(fs, e->t) || need_value(fs, e->f)) {
684       int fj = (e->k == VJMP) ? NO_JUMP : luaK_jump(fs);
685       p_f = code_loadbool(fs, reg, 0, 1);
686       p_t = code_loadbool(fs, reg, 1, 0);
687       luaK_patchtohere(fs, fj);
688     }
689     final = luaK_getlabel(fs);
690     patchlistaux(fs, e->f, final, reg, p_f);
691     patchlistaux(fs, e->t, final, reg, p_t);
692   }
693   e->f = e->t = NO_JUMP;
694   e->u.info = reg;
695   e->k = VNONRELOC;
696 }
697 
698 
699 /*
700 ** Ensures final expression result (including results from its jump
701 ** lists) is in next available register.
702 */
luaK_exp2nextreg(FuncState * fs,expdesc * e)703 void luaK_exp2nextreg (FuncState *fs, expdesc *e) {
704   luaK_dischargevars(fs, e);
705   freeexp(fs, e);
706   luaK_reserveregs(fs, 1);
707   exp2reg(fs, e, fs->freereg - 1);
708 }
709 
710 
711 /*
712 ** Ensures final expression result (including results from its jump
713 ** lists) is in some (any) register and return that register.
714 */
luaK_exp2anyreg(FuncState * fs,expdesc * e)715 int luaK_exp2anyreg (FuncState *fs, expdesc *e) {
716   luaK_dischargevars(fs, e);
717   if (e->k == VNONRELOC) {  /* expression already has a register? */
718     if (!hasjumps(e))  /* no jumps? */
719       return e->u.info;  /* result is already in a register */
720     if (e->u.info >= fs->nactvar) {  /* reg. is not a local? */
721       exp2reg(fs, e, e->u.info);  /* put final result in it */
722       return e->u.info;
723     }
724   }
725   luaK_exp2nextreg(fs, e);  /* otherwise, use next available register */
726   return e->u.info;
727 }
728 
729 
730 /*
731 ** Ensures final expression result is either in a register or in an
732 ** upvalue.
733 */
luaK_exp2anyregup(FuncState * fs,expdesc * e)734 void luaK_exp2anyregup (FuncState *fs, expdesc *e) {
735   if (e->k != VUPVAL || hasjumps(e))
736     luaK_exp2anyreg(fs, e);
737 }
738 
739 
740 /*
741 ** Ensures final expression result is either in a register or it is
742 ** a constant.
743 */
luaK_exp2val(FuncState * fs,expdesc * e)744 void luaK_exp2val (FuncState *fs, expdesc *e) {
745   if (hasjumps(e))
746     luaK_exp2anyreg(fs, e);
747   else
748     luaK_dischargevars(fs, e);
749 }
750 
751 
752 /*
753 ** Ensures final expression result is in a valid R/K index
754 ** (that is, it is either in a register or in 'k' with an index
755 ** in the range of R/K indices).
756 ** Returns R/K index.
757 */
luaK_exp2RK(FuncState * fs,expdesc * e)758 int luaK_exp2RK (FuncState *fs, expdesc *e) {
759   luaK_exp2val(fs, e);
760   switch (e->k) {  /* move constants to 'k' */
761     case VTRUE: e->u.info = boolK(fs, 1); goto vk;
762     case VFALSE: e->u.info = boolK(fs, 0); goto vk;
763     case VNIL: e->u.info = nilK(fs); goto vk;
764     case VKINT: e->u.info = luaK_intK(fs, e->u.ival); goto vk;
765     case VKFLT: e->u.info = luaK_numberK(fs, e->u.nval); goto vk;
766     case VK:
767      vk:
768       e->k = VK;
769       if (e->u.info <= MAXINDEXRK)  /* constant fits in 'argC'? */
770         return RKASK(e->u.info);
771       else break;
772     default: break;
773   }
774   /* not a constant in the right range: put it in a register */
775   return luaK_exp2anyreg(fs, e);
776 }
777 
778 
779 /*
780 ** Generate code to store result of expression 'ex' into variable 'var'.
781 */
luaK_storevar(FuncState * fs,expdesc * var,expdesc * ex)782 void luaK_storevar (FuncState *fs, expdesc *var, expdesc *ex) {
783   switch (var->k) {
784     case VLOCAL: {
785       freeexp(fs, ex);
786       exp2reg(fs, ex, var->u.info);  /* compute 'ex' into proper place */
787       return;
788     }
789     case VUPVAL: {
790       int e = luaK_exp2anyreg(fs, ex);
791       luaK_codeABC(fs, OP_SETUPVAL, e, var->u.info, 0);
792       break;
793     }
794     case VINDEXED: {
795       OpCode op = (var->u.ind.vt == VLOCAL) ? OP_SETTABLE : OP_SETTABUP;
796       int e = luaK_exp2RK(fs, ex);
797       luaK_codeABC(fs, op, var->u.ind.t, var->u.ind.idx, e);
798       break;
799     }
800     default: lua_assert(0);  /* invalid var kind to store */
801   }
802   freeexp(fs, ex);
803 }
804 
805 
806 /*
807 ** Emit SELF instruction (convert expression 'e' into 'e:key(e,').
808 */
luaK_self(FuncState * fs,expdesc * e,expdesc * key)809 void luaK_self (FuncState *fs, expdesc *e, expdesc *key) {
810   int ereg;
811   luaK_exp2anyreg(fs, e);
812   ereg = e->u.info;  /* register where 'e' was placed */
813   freeexp(fs, e);
814   e->u.info = fs->freereg;  /* base register for op_self */
815   e->k = VNONRELOC;  /* self expression has a fixed register */
816   luaK_reserveregs(fs, 2);  /* function and 'self' produced by op_self */
817   luaK_codeABC(fs, OP_SELF, e->u.info, ereg, luaK_exp2RK(fs, key));
818   freeexp(fs, key);
819 }
820 
821 
822 /*
823 ** Negate condition 'e' (where 'e' is a comparison).
824 */
negatecondition(FuncState * fs,expdesc * e)825 static void negatecondition (FuncState *fs, expdesc *e) {
826   Instruction *pc = getjumpcontrol(fs, e->u.info);
827   lua_assert(testTMode(GET_OPCODE(*pc)) && GET_OPCODE(*pc) != OP_TESTSET &&
828                                            GET_OPCODE(*pc) != OP_TEST);
829   SETARG_A(*pc, !(GETARG_A(*pc)));
830 }
831 
832 
833 /*
834 ** Emit instruction to jump if 'e' is 'cond' (that is, if 'cond'
835 ** is true, code will jump if 'e' is true.) Return jump position.
836 ** Optimize when 'e' is 'not' something, inverting the condition
837 ** and removing the 'not'.
838 */
jumponcond(FuncState * fs,expdesc * e,int cond)839 static int jumponcond (FuncState *fs, expdesc *e, int cond) {
840   if (e->k == VRELOCABLE) {
841     Instruction ie = getinstruction(fs, e);
842     if (GET_OPCODE(ie) == OP_NOT) {
843       fs->pc--;  /* remove previous OP_NOT */
844       return condjump(fs, OP_TEST, GETARG_B(ie), 0, !cond);
845     }
846     /* else go through */
847   }
848   discharge2anyreg(fs, e);
849   freeexp(fs, e);
850   return condjump(fs, OP_TESTSET, NO_REG, e->u.info, cond);
851 }
852 
853 
854 /*
855 ** Emit code to go through if 'e' is true, jump otherwise.
856 */
luaK_goiftrue(FuncState * fs,expdesc * e)857 void luaK_goiftrue (FuncState *fs, expdesc *e) {
858   int pc;  /* pc of new jump */
859   luaK_dischargevars(fs, e);
860   switch (e->k) {
861     case VJMP: {  /* condition? */
862       negatecondition(fs, e);  /* jump when it is false */
863       pc = e->u.info;  /* save jump position */
864       break;
865     }
866     case VK: case VKFLT: case VKINT: case VTRUE: {
867       pc = NO_JUMP;  /* always true; do nothing */
868       break;
869     }
870     default: {
871       pc = jumponcond(fs, e, 0);  /* jump when false */
872       break;
873     }
874   }
875   luaK_concat(fs, &e->f, pc);  /* insert new jump in false list */
876   luaK_patchtohere(fs, e->t);  /* true list jumps to here (to go through) */
877   e->t = NO_JUMP;
878 }
879 
880 
881 /*
882 ** Emit code to go through if 'e' is false, jump otherwise.
883 */
luaK_goiffalse(FuncState * fs,expdesc * e)884 void luaK_goiffalse (FuncState *fs, expdesc *e) {
885   int pc;  /* pc of new jump */
886   luaK_dischargevars(fs, e);
887   switch (e->k) {
888     case VJMP: {
889       pc = e->u.info;  /* already jump if true */
890       break;
891     }
892     case VNIL: case VFALSE: {
893       pc = NO_JUMP;  /* always false; do nothing */
894       break;
895     }
896     default: {
897       pc = jumponcond(fs, e, 1);  /* jump if true */
898       break;
899     }
900   }
901   luaK_concat(fs, &e->t, pc);  /* insert new jump in 't' list */
902   luaK_patchtohere(fs, e->f);  /* false list jumps to here (to go through) */
903   e->f = NO_JUMP;
904 }
905 
906 
907 /*
908 ** Code 'not e', doing constant folding.
909 */
codenot(FuncState * fs,expdesc * e)910 static void codenot (FuncState *fs, expdesc *e) {
911   luaK_dischargevars(fs, e);
912   switch (e->k) {
913     case VNIL: case VFALSE: {
914       e->k = VTRUE;  /* true == not nil == not false */
915       break;
916     }
917     case VK: case VKFLT: case VKINT: case VTRUE: {
918       e->k = VFALSE;  /* false == not "x" == not 0.5 == not 1 == not true */
919       break;
920     }
921     case VJMP: {
922       negatecondition(fs, e);
923       break;
924     }
925     case VRELOCABLE:
926     case VNONRELOC: {
927       discharge2anyreg(fs, e);
928       freeexp(fs, e);
929       e->u.info = luaK_codeABC(fs, OP_NOT, 0, e->u.info, 0);
930       e->k = VRELOCABLE;
931       break;
932     }
933     default: lua_assert(0);  /* cannot happen */
934   }
935   /* interchange true and false lists */
936   { int temp = e->f; e->f = e->t; e->t = temp; }
937   removevalues(fs, e->f);  /* values are useless when negated */
938   removevalues(fs, e->t);
939 }
940 
941 
942 /*
943 ** Create expression 't[k]'. 't' must have its final result already in a
944 ** register or upvalue.
945 */
luaK_indexed(FuncState * fs,expdesc * t,expdesc * k)946 void luaK_indexed (FuncState *fs, expdesc *t, expdesc *k) {
947   lua_assert(!hasjumps(t) && (vkisinreg(t->k) || t->k == VUPVAL));
948   t->u.ind.t = t->u.info;  /* register or upvalue index */
949   t->u.ind.idx = luaK_exp2RK(fs, k);  /* R/K index for key */
950   t->u.ind.vt = (t->k == VUPVAL) ? VUPVAL : VLOCAL;
951   t->k = VINDEXED;
952 }
953 
954 
955 /*
956 ** Return false if folding can raise an error.
957 ** Bitwise operations need operands convertible to integers; division
958 ** operations cannot have 0 as divisor.
959 */
validop(int op,TValue * v1,TValue * v2)960 static int validop (int op, TValue *v1, TValue *v2) {
961   switch (op) {
962     case LUA_OPBAND: case LUA_OPBOR: case LUA_OPBXOR:
963     case LUA_OPSHL: case LUA_OPSHR: case LUA_OPBNOT: {  /* conversion errors */
964       lua_Integer i;
965       return (tointeger(v1, &i) && tointeger(v2, &i));
966     }
967     case LUA_OPDIV: case LUA_OPIDIV: case LUA_OPMOD:  /* division by 0 */
968       return (nvalue(v2) != 0);
969     default: return 1;  /* everything else is valid */
970   }
971 }
972 
973 
974 /*
975 ** Try to "constant-fold" an operation; return 1 iff successful.
976 ** (In this case, 'e1' has the final result.)
977 */
constfolding(FuncState * fs,int op,expdesc * e1,const expdesc * e2)978 static int constfolding (FuncState *fs, int op, expdesc *e1,
979                                                 const expdesc *e2) {
980   TValue v1, v2, res;
981   if (!tonumeral(e1, &v1) || !tonumeral(e2, &v2) || !validop(op, &v1, &v2))
982     return 0;  /* non-numeric operands or not safe to fold */
983   luaO_arith(fs->ls->L, op, &v1, &v2, &res);  /* does operation */
984   if (ttisinteger(&res)) {
985     e1->k = VKINT;
986     e1->u.ival = ivalue(&res);
987   }
988   else {  /* folds neither NaN nor 0.0 (to avoid problems with -0.0) */
989     lua_Number n = fltvalue(&res);
990     if (luai_numisnan(n) || n == 0)
991       return 0;
992     e1->k = VKFLT;
993     e1->u.nval = n;
994   }
995   return 1;
996 }
997 
998 
999 /*
1000 ** Emit code for unary expressions that "produce values"
1001 ** (everything but 'not').
1002 ** Expression to produce final result will be encoded in 'e'.
1003 */
codeunexpval(FuncState * fs,OpCode op,expdesc * e,int line)1004 static void codeunexpval (FuncState *fs, OpCode op, expdesc *e, int line) {
1005   int r = luaK_exp2anyreg(fs, e);  /* opcodes operate only on registers */
1006   freeexp(fs, e);
1007   e->u.info = luaK_codeABC(fs, op, 0, r, 0);  /* generate opcode */
1008   e->k = VRELOCABLE;  /* all those operations are relocatable */
1009   luaK_fixline(fs, line);
1010 }
1011 
1012 
1013 /*
1014 ** Emit code for binary expressions that "produce values"
1015 ** (everything but logical operators 'and'/'or' and comparison
1016 ** operators).
1017 ** Expression to produce final result will be encoded in 'e1'.
1018 ** Because 'luaK_exp2RK' can free registers, its calls must be
1019 ** in "stack order" (that is, first on 'e2', which may have more
1020 ** recent registers to be released).
1021 */
codebinexpval(FuncState * fs,OpCode op,expdesc * e1,expdesc * e2,int line)1022 static void codebinexpval (FuncState *fs, OpCode op,
1023                            expdesc *e1, expdesc *e2, int line) {
1024   int rk2 = luaK_exp2RK(fs, e2);  /* both operands are "RK" */
1025   int rk1 = luaK_exp2RK(fs, e1);
1026   freeexps(fs, e1, e2);
1027   e1->u.info = luaK_codeABC(fs, op, 0, rk1, rk2);  /* generate opcode */
1028   e1->k = VRELOCABLE;  /* all those operations are relocatable */
1029   luaK_fixline(fs, line);
1030 }
1031 
1032 
1033 /*
1034 ** Emit code for comparisons.
1035 ** 'e1' was already put in R/K form by 'luaK_infix'.
1036 */
codecomp(FuncState * fs,BinOpr opr,expdesc * e1,expdesc * e2)1037 static void codecomp (FuncState *fs, BinOpr opr, expdesc *e1, expdesc *e2) {
1038   int rk1 = (e1->k == VK) ? RKASK(e1->u.info)
1039                           : check_exp(e1->k == VNONRELOC, e1->u.info);
1040   int rk2 = luaK_exp2RK(fs, e2);
1041   freeexps(fs, e1, e2);
1042   switch (opr) {
1043     case OPR_NE: {  /* '(a ~= b)' ==> 'not (a == b)' */
1044       e1->u.info = condjump(fs, OP_EQ, 0, rk1, rk2);
1045       break;
1046     }
1047     case OPR_GT: case OPR_GE: {
1048       /* '(a > b)' ==> '(b < a)';  '(a >= b)' ==> '(b <= a)' */
1049       OpCode op = cast(OpCode, (opr - OPR_NE) + OP_EQ);
1050       e1->u.info = condjump(fs, op, 1, rk2, rk1);  /* invert operands */
1051       break;
1052     }
1053     default: {  /* '==', '<', '<=' use their own opcodes */
1054       OpCode op = cast(OpCode, (opr - OPR_EQ) + OP_EQ);
1055       e1->u.info = condjump(fs, op, 1, rk1, rk2);
1056       break;
1057     }
1058   }
1059   e1->k = VJMP;
1060 }
1061 
1062 
1063 /*
1064 ** Aplly prefix operation 'op' to expression 'e'.
1065 */
luaK_prefix(FuncState * fs,UnOpr op,expdesc * e,int line)1066 void luaK_prefix (FuncState *fs, UnOpr op, expdesc *e, int line) {
1067   static const expdesc ef = {VKINT, {0}, NO_JUMP, NO_JUMP};
1068   switch (op) {
1069     case OPR_MINUS: case OPR_BNOT:  /* use 'ef' as fake 2nd operand */
1070       if (constfolding(fs, op + LUA_OPUNM, e, &ef))
1071         break;
1072       /* FALLTHROUGH */
1073     case OPR_LEN:
1074       codeunexpval(fs, cast(OpCode, op + OP_UNM), e, line);
1075       break;
1076     case OPR_NOT: codenot(fs, e); break;
1077     default: lua_assert(0);
1078   }
1079 }
1080 
1081 
1082 /*
1083 ** Process 1st operand 'v' of binary operation 'op' before reading
1084 ** 2nd operand.
1085 */
luaK_infix(FuncState * fs,BinOpr op,expdesc * v)1086 void luaK_infix (FuncState *fs, BinOpr op, expdesc *v) {
1087   switch (op) {
1088     case OPR_AND: {
1089       luaK_goiftrue(fs, v);  /* go ahead only if 'v' is true */
1090       break;
1091     }
1092     case OPR_OR: {
1093       luaK_goiffalse(fs, v);  /* go ahead only if 'v' is false */
1094       break;
1095     }
1096     case OPR_CONCAT: {
1097       luaK_exp2nextreg(fs, v);  /* operand must be on the 'stack' */
1098       break;
1099     }
1100     case OPR_ADD: case OPR_SUB:
1101     case OPR_MUL: case OPR_DIV: case OPR_IDIV:
1102     case OPR_MOD: case OPR_POW:
1103     case OPR_BAND: case OPR_BOR: case OPR_BXOR:
1104     case OPR_SHL: case OPR_SHR: {
1105       if (!tonumeral(v, NULL))
1106         luaK_exp2RK(fs, v);
1107       /* else keep numeral, which may be folded with 2nd operand */
1108       break;
1109     }
1110     default: {
1111       luaK_exp2RK(fs, v);
1112       break;
1113     }
1114   }
1115 }
1116 
1117 
1118 /*
1119 ** Finalize code for binary operation, after reading 2nd operand.
1120 ** For '(a .. b .. c)' (which is '(a .. (b .. c))', because
1121 ** concatenation is right associative), merge second CONCAT into first
1122 ** one.
1123 */
luaK_posfix(FuncState * fs,BinOpr op,expdesc * e1,expdesc * e2,int line)1124 void luaK_posfix (FuncState *fs, BinOpr op,
1125                   expdesc *e1, expdesc *e2, int line) {
1126   switch (op) {
1127     case OPR_AND: {
1128       lua_assert(e1->t == NO_JUMP);  /* list closed by 'luK_infix' */
1129       luaK_dischargevars(fs, e2);
1130       luaK_concat(fs, &e2->f, e1->f);
1131       *e1 = *e2;
1132       break;
1133     }
1134     case OPR_OR: {
1135       lua_assert(e1->f == NO_JUMP);  /* list closed by 'luK_infix' */
1136       luaK_dischargevars(fs, e2);
1137       luaK_concat(fs, &e2->t, e1->t);
1138       *e1 = *e2;
1139       break;
1140     }
1141     case OPR_CONCAT: {
1142       luaK_exp2val(fs, e2);
1143       if (e2->k == VRELOCABLE &&
1144           GET_OPCODE(getinstruction(fs, e2)) == OP_CONCAT) {
1145         lua_assert(e1->u.info == GETARG_B(getinstruction(fs, e2))-1);
1146         freeexp(fs, e1);
1147         SETARG_B(getinstruction(fs, e2), e1->u.info);
1148         e1->k = VRELOCABLE; e1->u.info = e2->u.info;
1149       }
1150       else {
1151         luaK_exp2nextreg(fs, e2);  /* operand must be on the 'stack' */
1152         codebinexpval(fs, OP_CONCAT, e1, e2, line);
1153       }
1154       break;
1155     }
1156     case OPR_ADD: case OPR_SUB: case OPR_MUL: case OPR_DIV:
1157     case OPR_IDIV: case OPR_MOD: case OPR_POW:
1158     case OPR_BAND: case OPR_BOR: case OPR_BXOR:
1159     case OPR_SHL: case OPR_SHR: {
1160       if (!constfolding(fs, op + LUA_OPADD, e1, e2))
1161         codebinexpval(fs, cast(OpCode, op + OP_ADD), e1, e2, line);
1162       break;
1163     }
1164     case OPR_EQ: case OPR_LT: case OPR_LE:
1165     case OPR_NE: case OPR_GT: case OPR_GE: {
1166       codecomp(fs, op, e1, e2);
1167       break;
1168     }
1169     default: lua_assert(0);
1170   }
1171 }
1172 
1173 
1174 /*
1175 ** Change line information associated with current position.
1176 */
luaK_fixline(FuncState * fs,int line)1177 void luaK_fixline (FuncState *fs, int line) {
1178   fs->f->lineinfo[fs->pc - 1] = line;
1179 }
1180 
1181 
1182 /*
1183 ** Emit a SETLIST instruction.
1184 ** 'base' is register that keeps table;
1185 ** 'nelems' is #table plus those to be stored now;
1186 ** 'tostore' is number of values (in registers 'base + 1',...) to add to
1187 ** table (or LUA_MULTRET to add up to stack top).
1188 */
luaK_setlist(FuncState * fs,int base,int nelems,int tostore)1189 void luaK_setlist (FuncState *fs, int base, int nelems, int tostore) {
1190   int c =  (nelems - 1)/LFIELDS_PER_FLUSH + 1;
1191   int b = (tostore == LUA_MULTRET) ? 0 : tostore;
1192   lua_assert(tostore != 0 && tostore <= LFIELDS_PER_FLUSH);
1193   if (c <= MAXARG_C)
1194     luaK_codeABC(fs, OP_SETLIST, base, b, c);
1195   else if (c <= MAXARG_Ax) {
1196     luaK_codeABC(fs, OP_SETLIST, base, b, 0);
1197     codeextraarg(fs, c);
1198   }
1199   else
1200     luaX_syntaxerror(fs->ls, "constructor too long");
1201   fs->freereg = base + 1;  /* free registers with list values */
1202 }
1203 
1204