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      1 /*
      2 ** $Id: lcode.c,v 2.62 2012/08/16 17:34:28 roberto Exp $
      3 ** Code generator for Lua
      4 ** See Copyright Notice in lua.h
      5 */
      6 
      7 
      8 #include <stdlib.h>
      9 
     10 #define lcode_c
     11 #define LUA_CORE
     12 
     13 #include "lua.h"
     14 
     15 #include "lcode.h"
     16 #include "ldebug.h"
     17 #include "ldo.h"
     18 #include "lgc.h"
     19 #include "llex.h"
     20 #include "lmem.h"
     21 #include "lobject.h"
     22 #include "lopcodes.h"
     23 #include "lparser.h"
     24 #include "lstring.h"
     25 #include "ltable.h"
     26 #include "lvm.h"
     27 
     28 
     29 #define hasjumps(e)	((e)->t != (e)->f)
     30 
     31 
     32 static int isnumeral(expdesc *e) {
     33   return (e->k == VKNUM && e->t == NO_JUMP && e->f == NO_JUMP);
     34 }
     35 
     36 
     37 void luaK_nil (FuncState *fs, int from, int n) {
     38   Instruction *previous;
     39   int l = from + n - 1;  /* last register to set nil */
     40   if (fs->pc > fs->lasttarget) {  /* no jumps to current position? */
     41     previous = &fs->f->code[fs->pc-1];
     42     if (GET_OPCODE(*previous) == OP_LOADNIL) {
     43       int pfrom = GETARG_A(*previous);
     44       int pl = pfrom + GETARG_B(*previous);
     45       if ((pfrom <= from && from <= pl + 1) ||
     46           (from <= pfrom && pfrom <= l + 1)) {  /* can connect both? */
     47         if (pfrom < from) from = pfrom;  /* from = min(from, pfrom) */
     48         if (pl > l) l = pl;  /* l = max(l, pl) */
     49         SETARG_A(*previous, from);
     50         SETARG_B(*previous, l - from);
     51         return;
     52       }
     53     }  /* else go through */
     54   }
     55   luaK_codeABC(fs, OP_LOADNIL, from, n - 1, 0);  /* else no optimization */
     56 }
     57 
     58 
     59 int luaK_jump (FuncState *fs) {
     60   int jpc = fs->jpc;  /* save list of jumps to here */
     61   int j;
     62   fs->jpc = NO_JUMP;
     63   j = luaK_codeAsBx(fs, OP_JMP, 0, NO_JUMP);
     64   luaK_concat(fs, &j, jpc);  /* keep them on hold */
     65   return j;
     66 }
     67 
     68 
     69 void luaK_ret (FuncState *fs, int first, int nret) {
     70   luaK_codeABC(fs, OP_RETURN, first, nret+1, 0);
     71 }
     72 
     73 
     74 static int condjump (FuncState *fs, OpCode op, int A, int B, int C) {
     75   luaK_codeABC(fs, op, A, B, C);
     76   return luaK_jump(fs);
     77 }
     78 
     79 
     80 static void fixjump (FuncState *fs, int pc, int dest) {
     81   Instruction *jmp = &fs->f->code[pc];
     82   int offset = dest-(pc+1);
     83   lua_assert(dest != NO_JUMP);
     84   if (abs(offset) > MAXARG_sBx)
     85     luaX_syntaxerror(fs->ls, "control structure too long");
     86   SETARG_sBx(*jmp, offset);
     87 }
     88 
     89 
     90 /*
     91 ** returns current `pc' and marks it as a jump target (to avoid wrong
     92 ** optimizations with consecutive instructions not in the same basic block).
     93 */
     94 int luaK_getlabel (FuncState *fs) {
     95   fs->lasttarget = fs->pc;
     96   return fs->pc;
     97 }
     98 
     99 
    100 static int getjump (FuncState *fs, int pc) {
    101   int offset = GETARG_sBx(fs->f->code[pc]);
    102   if (offset == NO_JUMP)  /* point to itself represents end of list */
    103     return NO_JUMP;  /* end of list */
    104   else
    105     return (pc+1)+offset;  /* turn offset into absolute position */
    106 }
    107 
    108 
    109 static Instruction *getjumpcontrol (FuncState *fs, int pc) {
    110   Instruction *pi = &fs->f->code[pc];
    111   if (pc >= 1 && testTMode(GET_OPCODE(*(pi-1))))
    112     return pi-1;
    113   else
    114     return pi;
    115 }
    116 
    117 
    118 /*
    119 ** check whether list has any jump that do not produce a value
    120 ** (or produce an inverted value)
    121 */
    122 static int need_value (FuncState *fs, int list) {
    123   for (; list != NO_JUMP; list = getjump(fs, list)) {
    124     Instruction i = *getjumpcontrol(fs, list);
    125     if (GET_OPCODE(i) != OP_TESTSET) return 1;
    126   }
    127   return 0;  /* not found */
    128 }
    129 
    130 
    131 static int patchtestreg (FuncState *fs, int node, int reg) {
    132   Instruction *i = getjumpcontrol(fs, node);
    133   if (GET_OPCODE(*i) != OP_TESTSET)
    134     return 0;  /* cannot patch other instructions */
    135   if (reg != NO_REG && reg != GETARG_B(*i))
    136     SETARG_A(*i, reg);
    137   else  /* no register to put value or register already has the value */
    138     *i = CREATE_ABC(OP_TEST, GETARG_B(*i), 0, GETARG_C(*i));
    139 
    140   return 1;
    141 }
    142 
    143 
    144 static void removevalues (FuncState *fs, int list) {
    145   for (; list != NO_JUMP; list = getjump(fs, list))
    146       patchtestreg(fs, list, NO_REG);
    147 }
    148 
    149 
    150 static void patchlistaux (FuncState *fs, int list, int vtarget, int reg,
    151                           int dtarget) {
    152   while (list != NO_JUMP) {
    153     int next = getjump(fs, list);
    154     if (patchtestreg(fs, list, reg))
    155       fixjump(fs, list, vtarget);
    156     else
    157       fixjump(fs, list, dtarget);  /* jump to default target */
    158     list = next;
    159   }
    160 }
    161 
    162 
    163 static void dischargejpc (FuncState *fs) {
    164   patchlistaux(fs, fs->jpc, fs->pc, NO_REG, fs->pc);
    165   fs->jpc = NO_JUMP;
    166 }
    167 
    168 
    169 void luaK_patchlist (FuncState *fs, int list, int target) {
    170   if (target == fs->pc)
    171     luaK_patchtohere(fs, list);
    172   else {
    173     lua_assert(target < fs->pc);
    174     patchlistaux(fs, list, target, NO_REG, target);
    175   }
    176 }
    177 
    178 
    179 LUAI_FUNC void luaK_patchclose (FuncState *fs, int list, int level) {
    180   level++;  /* argument is +1 to reserve 0 as non-op */
    181   while (list != NO_JUMP) {
    182     int next = getjump(fs, list);
    183     lua_assert(GET_OPCODE(fs->f->code[list]) == OP_JMP &&
    184                 (GETARG_A(fs->f->code[list]) == 0 ||
    185                  GETARG_A(fs->f->code[list]) >= level));
    186     SETARG_A(fs->f->code[list], level);
    187     list = next;
    188   }
    189 }
    190 
    191 
    192 void luaK_patchtohere (FuncState *fs, int list) {
    193   luaK_getlabel(fs);
    194   luaK_concat(fs, &fs->jpc, list);
    195 }
    196 
    197 
    198 void luaK_concat (FuncState *fs, int *l1, int l2) {
    199   if (l2 == NO_JUMP) return;
    200   else if (*l1 == NO_JUMP)
    201     *l1 = l2;
    202   else {
    203     int list = *l1;
    204     int next;
    205     while ((next = getjump(fs, list)) != NO_JUMP)  /* find last element */
    206       list = next;
    207     fixjump(fs, list, l2);
    208   }
    209 }
    210 
    211 
    212 static int luaK_code (FuncState *fs, Instruction i) {
    213   Proto *f = fs->f;
    214   dischargejpc(fs);  /* `pc' will change */
    215   /* put new instruction in code array */
    216   luaM_growvector(fs->ls->L, f->code, fs->pc, f->sizecode, Instruction,
    217                   MAX_INT, "opcodes");
    218   f->code[fs->pc] = i;
    219   /* save corresponding line information */
    220   luaM_growvector(fs->ls->L, f->lineinfo, fs->pc, f->sizelineinfo, int,
    221                   MAX_INT, "opcodes");
    222   f->lineinfo[fs->pc] = fs->ls->lastline;
    223   return fs->pc++;
    224 }
    225 
    226 
    227 int luaK_codeABC (FuncState *fs, OpCode o, int a, int b, int c) {
    228   lua_assert(getOpMode(o) == iABC);
    229   lua_assert(getBMode(o) != OpArgN || b == 0);
    230   lua_assert(getCMode(o) != OpArgN || c == 0);
    231   lua_assert(a <= MAXARG_A && b <= MAXARG_B && c <= MAXARG_C);
    232   return luaK_code(fs, CREATE_ABC(o, a, b, c));
    233 }
    234 
    235 
    236 int luaK_codeABx (FuncState *fs, OpCode o, int a, unsigned int bc) {
    237   lua_assert(getOpMode(o) == iABx || getOpMode(o) == iAsBx);
    238   lua_assert(getCMode(o) == OpArgN);
    239   lua_assert(a <= MAXARG_A && bc <= MAXARG_Bx);
    240   return luaK_code(fs, CREATE_ABx(o, a, bc));
    241 }
    242 
    243 
    244 static int codeextraarg (FuncState *fs, int a) {
    245   lua_assert(a <= MAXARG_Ax);
    246   return luaK_code(fs, CREATE_Ax(OP_EXTRAARG, a));
    247 }
    248 
    249 
    250 int luaK_codek (FuncState *fs, int reg, int k) {
    251   if (k <= MAXARG_Bx)
    252     return luaK_codeABx(fs, OP_LOADK, reg, k);
    253   else {
    254     int p = luaK_codeABx(fs, OP_LOADKX, reg, 0);
    255     codeextraarg(fs, k);
    256     return p;
    257   }
    258 }
    259 
    260 
    261 void luaK_checkstack (FuncState *fs, int n) {
    262   int newstack = fs->freereg + n;
    263   if (newstack > fs->f->maxstacksize) {
    264     if (newstack >= MAXSTACK)
    265       luaX_syntaxerror(fs->ls, "function or expression too complex");
    266     fs->f->maxstacksize = cast_byte(newstack);
    267   }
    268 }
    269 
    270 
    271 void luaK_reserveregs (FuncState *fs, int n) {
    272   luaK_checkstack(fs, n);
    273   fs->freereg += n;
    274 }
    275 
    276 
    277 static void freereg (FuncState *fs, int reg) {
    278   if (!ISK(reg) && reg >= fs->nactvar) {
    279     fs->freereg--;
    280     lua_assert(reg == fs->freereg);
    281   }
    282 }
    283 
    284 
    285 static void freeexp (FuncState *fs, expdesc *e) {
    286   if (e->k == VNONRELOC)
    287     freereg(fs, e->u.info);
    288 }
    289 
    290 
    291 static int addk (FuncState *fs, TValue *key, TValue *v) {
    292   lua_State *L = fs->ls->L;
    293   TValue *idx = luaH_set(L, fs->h, key);
    294   Proto *f = fs->f;
    295   int k, oldsize;
    296   if (ttisnumber(idx)) {
    297     lua_Number n = nvalue(idx);
    298     lua_number2int(k, n);
    299     if (luaV_rawequalobj(&f->k[k], v))
    300       return k;
    301     /* else may be a collision (e.g., between 0.0 and "\0\0\0\0\0\0\0\0");
    302        go through and create a new entry for this value */
    303   }
    304   /* constant not found; create a new entry */
    305   oldsize = f->sizek;
    306   k = fs->nk;
    307   /* numerical value does not need GC barrier;
    308      table has no metatable, so it does not need to invalidate cache */
    309   setnvalue(idx, cast_num(k));
    310   luaM_growvector(L, f->k, k, f->sizek, TValue, MAXARG_Ax, "constants");
    311   while (oldsize < f->sizek) setnilvalue(&f->k[oldsize++]);
    312   setobj(L, &f->k[k], v);
    313   fs->nk++;
    314   luaC_barrier(L, f, v);
    315   return k;
    316 }
    317 
    318 
    319 int luaK_stringK (FuncState *fs, TString *s) {
    320   TValue o;
    321   setsvalue(fs->ls->L, &o, s);
    322   return addk(fs, &o, &o);
    323 }
    324 
    325 
    326 int luaK_numberK (FuncState *fs, lua_Number r) {
    327   int n;
    328   lua_State *L = fs->ls->L;
    329   TValue o;
    330   setnvalue(&o, r);
    331   if (r == 0 || luai_numisnan(NULL, r)) {  /* handle -0 and NaN */
    332     /* use raw representation as key to avoid numeric problems */
    333     setsvalue(L, L->top++, luaS_newlstr(L, (char *)&r, sizeof(r)));
    334     n = addk(fs, L->top - 1, &o);
    335     L->top--;
    336   }
    337   else
    338     n = addk(fs, &o, &o);  /* regular case */
    339   return n;
    340 }
    341 
    342 
    343 static int boolK (FuncState *fs, int b) {
    344   TValue o;
    345   setbvalue(&o, b);
    346   return addk(fs, &o, &o);
    347 }
    348 
    349 
    350 static int nilK (FuncState *fs) {
    351   TValue k, v;
    352   setnilvalue(&v);
    353   /* cannot use nil as key; instead use table itself to represent nil */
    354   sethvalue(fs->ls->L, &k, fs->h);
    355   return addk(fs, &k, &v);
    356 }
    357 
    358 
    359 void luaK_setreturns (FuncState *fs, expdesc *e, int nresults) {
    360   if (e->k == VCALL) {  /* expression is an open function call? */
    361     SETARG_C(getcode(fs, e), nresults+1);
    362   }
    363   else if (e->k == VVARARG) {
    364     SETARG_B(getcode(fs, e), nresults+1);
    365     SETARG_A(getcode(fs, e), fs->freereg);
    366     luaK_reserveregs(fs, 1);
    367   }
    368 }
    369 
    370 
    371 void luaK_setoneret (FuncState *fs, expdesc *e) {
    372   if (e->k == VCALL) {  /* expression is an open function call? */
    373     e->k = VNONRELOC;
    374     e->u.info = GETARG_A(getcode(fs, e));
    375   }
    376   else if (e->k == VVARARG) {
    377     SETARG_B(getcode(fs, e), 2);
    378     e->k = VRELOCABLE;  /* can relocate its simple result */
    379   }
    380 }
    381 
    382 
    383 void luaK_dischargevars (FuncState *fs, expdesc *e) {
    384   switch (e->k) {
    385     case VLOCAL: {
    386       e->k = VNONRELOC;
    387       break;
    388     }
    389     case VUPVAL: {
    390       e->u.info = luaK_codeABC(fs, OP_GETUPVAL, 0, e->u.info, 0);
    391       e->k = VRELOCABLE;
    392       break;
    393     }
    394     case VINDEXED: {
    395       OpCode op = OP_GETTABUP;  /* assume 't' is in an upvalue */
    396       freereg(fs, e->u.ind.idx);
    397       if (e->u.ind.vt == VLOCAL) {  /* 't' is in a register? */
    398         freereg(fs, e->u.ind.t);
    399         op = OP_GETTABLE;
    400       }
    401       e->u.info = luaK_codeABC(fs, op, 0, e->u.ind.t, e->u.ind.idx);
    402       e->k = VRELOCABLE;
    403       break;
    404     }
    405     case VVARARG:
    406     case VCALL: {
    407       luaK_setoneret(fs, e);
    408       break;
    409     }
    410     default: break;  /* there is one value available (somewhere) */
    411   }
    412 }
    413 
    414 
    415 static int code_label (FuncState *fs, int A, int b, int jump) {
    416   luaK_getlabel(fs);  /* those instructions may be jump targets */
    417   return luaK_codeABC(fs, OP_LOADBOOL, A, b, jump);
    418 }
    419 
    420 
    421 static void discharge2reg (FuncState *fs, expdesc *e, int reg) {
    422   luaK_dischargevars(fs, e);
    423   switch (e->k) {
    424     case VNIL: {
    425       luaK_nil(fs, reg, 1);
    426       break;
    427     }
    428     case VFALSE: case VTRUE: {
    429       luaK_codeABC(fs, OP_LOADBOOL, reg, e->k == VTRUE, 0);
    430       break;
    431     }
    432     case VK: {
    433       luaK_codek(fs, reg, e->u.info);
    434       break;
    435     }
    436     case VKNUM: {
    437       luaK_codek(fs, reg, luaK_numberK(fs, e->u.nval));
    438       break;
    439     }
    440     case VRELOCABLE: {
    441       Instruction *pc = &getcode(fs, e);
    442       SETARG_A(*pc, reg);
    443       break;
    444     }
    445     case VNONRELOC: {
    446       if (reg != e->u.info)
    447         luaK_codeABC(fs, OP_MOVE, reg, e->u.info, 0);
    448       break;
    449     }
    450     default: {
    451       lua_assert(e->k == VVOID || e->k == VJMP);
    452       return;  /* nothing to do... */
    453     }
    454   }
    455   e->u.info = reg;
    456   e->k = VNONRELOC;
    457 }
    458 
    459 
    460 static void discharge2anyreg (FuncState *fs, expdesc *e) {
    461   if (e->k != VNONRELOC) {
    462     luaK_reserveregs(fs, 1);
    463     discharge2reg(fs, e, fs->freereg-1);
    464   }
    465 }
    466 
    467 
    468 static void exp2reg (FuncState *fs, expdesc *e, int reg) {
    469   discharge2reg(fs, e, reg);
    470   if (e->k == VJMP)
    471     luaK_concat(fs, &e->t, e->u.info);  /* put this jump in `t' list */
    472   if (hasjumps(e)) {
    473     int final;  /* position after whole expression */
    474     int p_f = NO_JUMP;  /* position of an eventual LOAD false */
    475     int p_t = NO_JUMP;  /* position of an eventual LOAD true */
    476     if (need_value(fs, e->t) || need_value(fs, e->f)) {
    477       int fj = (e->k == VJMP) ? NO_JUMP : luaK_jump(fs);
    478       p_f = code_label(fs, reg, 0, 1);
    479       p_t = code_label(fs, reg, 1, 0);
    480       luaK_patchtohere(fs, fj);
    481     }
    482     final = luaK_getlabel(fs);
    483     patchlistaux(fs, e->f, final, reg, p_f);
    484     patchlistaux(fs, e->t, final, reg, p_t);
    485   }
    486   e->f = e->t = NO_JUMP;
    487   e->u.info = reg;
    488   e->k = VNONRELOC;
    489 }
    490 
    491 
    492 void luaK_exp2nextreg (FuncState *fs, expdesc *e) {
    493   luaK_dischargevars(fs, e);
    494   freeexp(fs, e);
    495   luaK_reserveregs(fs, 1);
    496   exp2reg(fs, e, fs->freereg - 1);
    497 }
    498 
    499 
    500 int luaK_exp2anyreg (FuncState *fs, expdesc *e) {
    501   luaK_dischargevars(fs, e);
    502   if (e->k == VNONRELOC) {
    503     if (!hasjumps(e)) return e->u.info;  /* exp is already in a register */
    504     if (e->u.info >= fs->nactvar) {  /* reg. is not a local? */
    505       exp2reg(fs, e, e->u.info);  /* put value on it */
    506       return e->u.info;
    507     }
    508   }
    509   luaK_exp2nextreg(fs, e);  /* default */
    510   return e->u.info;
    511 }
    512 
    513 
    514 void luaK_exp2anyregup (FuncState *fs, expdesc *e) {
    515   if (e->k != VUPVAL || hasjumps(e))
    516     luaK_exp2anyreg(fs, e);
    517 }
    518 
    519 
    520 void luaK_exp2val (FuncState *fs, expdesc *e) {
    521   if (hasjumps(e))
    522     luaK_exp2anyreg(fs, e);
    523   else
    524     luaK_dischargevars(fs, e);
    525 }
    526 
    527 
    528 int luaK_exp2RK (FuncState *fs, expdesc *e) {
    529   luaK_exp2val(fs, e);
    530   switch (e->k) {
    531     case VTRUE:
    532     case VFALSE:
    533     case VNIL: {
    534       if (fs->nk <= MAXINDEXRK) {  /* constant fits in RK operand? */
    535         e->u.info = (e->k == VNIL) ? nilK(fs) : boolK(fs, (e->k == VTRUE));
    536         e->k = VK;
    537         return RKASK(e->u.info);
    538       }
    539       else break;
    540     }
    541     case VKNUM: {
    542       e->u.info = luaK_numberK(fs, e->u.nval);
    543       e->k = VK;
    544       /* go through */
    545     }
    546     case VK: {
    547       if (e->u.info <= MAXINDEXRK)  /* constant fits in argC? */
    548         return RKASK(e->u.info);
    549       else break;
    550     }
    551     default: break;
    552   }
    553   /* not a constant in the right range: put it in a register */
    554   return luaK_exp2anyreg(fs, e);
    555 }
    556 
    557 
    558 void luaK_storevar (FuncState *fs, expdesc *var, expdesc *ex) {
    559   switch (var->k) {
    560     case VLOCAL: {
    561       freeexp(fs, ex);
    562       exp2reg(fs, ex, var->u.info);
    563       return;
    564     }
    565     case VUPVAL: {
    566       int e = luaK_exp2anyreg(fs, ex);
    567       luaK_codeABC(fs, OP_SETUPVAL, e, var->u.info, 0);
    568       break;
    569     }
    570     case VINDEXED: {
    571       OpCode op = (var->u.ind.vt == VLOCAL) ? OP_SETTABLE : OP_SETTABUP;
    572       int e = luaK_exp2RK(fs, ex);
    573       luaK_codeABC(fs, op, var->u.ind.t, var->u.ind.idx, e);
    574       break;
    575     }
    576     default: {
    577       lua_assert(0);  /* invalid var kind to store */
    578       break;
    579     }
    580   }
    581   freeexp(fs, ex);
    582 }
    583 
    584 
    585 void luaK_self (FuncState *fs, expdesc *e, expdesc *key) {
    586   int ereg;
    587   luaK_exp2anyreg(fs, e);
    588   ereg = e->u.info;  /* register where 'e' was placed */
    589   freeexp(fs, e);
    590   e->u.info = fs->freereg;  /* base register for op_self */
    591   e->k = VNONRELOC;
    592   luaK_reserveregs(fs, 2);  /* function and 'self' produced by op_self */
    593   luaK_codeABC(fs, OP_SELF, e->u.info, ereg, luaK_exp2RK(fs, key));
    594   freeexp(fs, key);
    595 }
    596 
    597 
    598 static void invertjump (FuncState *fs, expdesc *e) {
    599   Instruction *pc = getjumpcontrol(fs, e->u.info);
    600   lua_assert(testTMode(GET_OPCODE(*pc)) && GET_OPCODE(*pc) != OP_TESTSET &&
    601                                            GET_OPCODE(*pc) != OP_TEST);
    602   SETARG_A(*pc, !(GETARG_A(*pc)));
    603 }
    604 
    605 
    606 static int jumponcond (FuncState *fs, expdesc *e, int cond) {
    607   if (e->k == VRELOCABLE) {
    608     Instruction ie = getcode(fs, e);
    609     if (GET_OPCODE(ie) == OP_NOT) {
    610       fs->pc--;  /* remove previous OP_NOT */
    611       return condjump(fs, OP_TEST, GETARG_B(ie), 0, !cond);
    612     }
    613     /* else go through */
    614   }
    615   discharge2anyreg(fs, e);
    616   freeexp(fs, e);
    617   return condjump(fs, OP_TESTSET, NO_REG, e->u.info, cond);
    618 }
    619 
    620 
    621 void luaK_goiftrue (FuncState *fs, expdesc *e) {
    622   int pc;  /* pc of last jump */
    623   luaK_dischargevars(fs, e);
    624   switch (e->k) {
    625     case VJMP: {
    626       invertjump(fs, e);
    627       pc = e->u.info;
    628       break;
    629     }
    630     case VK: case VKNUM: case VTRUE: {
    631       pc = NO_JUMP;  /* always true; do nothing */
    632       break;
    633     }
    634     default: {
    635       pc = jumponcond(fs, e, 0);
    636       break;
    637     }
    638   }
    639   luaK_concat(fs, &e->f, pc);  /* insert last jump in `f' list */
    640   luaK_patchtohere(fs, e->t);
    641   e->t = NO_JUMP;
    642 }
    643 
    644 
    645 void luaK_goiffalse (FuncState *fs, expdesc *e) {
    646   int pc;  /* pc of last jump */
    647   luaK_dischargevars(fs, e);
    648   switch (e->k) {
    649     case VJMP: {
    650       pc = e->u.info;
    651       break;
    652     }
    653     case VNIL: case VFALSE: {
    654       pc = NO_JUMP;  /* always false; do nothing */
    655       break;
    656     }
    657     default: {
    658       pc = jumponcond(fs, e, 1);
    659       break;
    660     }
    661   }
    662   luaK_concat(fs, &e->t, pc);  /* insert last jump in `t' list */
    663   luaK_patchtohere(fs, e->f);
    664   e->f = NO_JUMP;
    665 }
    666 
    667 
    668 static void codenot (FuncState *fs, expdesc *e) {
    669   luaK_dischargevars(fs, e);
    670   switch (e->k) {
    671     case VNIL: case VFALSE: {
    672       e->k = VTRUE;
    673       break;
    674     }
    675     case VK: case VKNUM: case VTRUE: {
    676       e->k = VFALSE;
    677       break;
    678     }
    679     case VJMP: {
    680       invertjump(fs, e);
    681       break;
    682     }
    683     case VRELOCABLE:
    684     case VNONRELOC: {
    685       discharge2anyreg(fs, e);
    686       freeexp(fs, e);
    687       e->u.info = luaK_codeABC(fs, OP_NOT, 0, e->u.info, 0);
    688       e->k = VRELOCABLE;
    689       break;
    690     }
    691     default: {
    692       lua_assert(0);  /* cannot happen */
    693       break;
    694     }
    695   }
    696   /* interchange true and false lists */
    697   { int temp = e->f; e->f = e->t; e->t = temp; }
    698   removevalues(fs, e->f);
    699   removevalues(fs, e->t);
    700 }
    701 
    702 
    703 void luaK_indexed (FuncState *fs, expdesc *t, expdesc *k) {
    704   lua_assert(!hasjumps(t));
    705   t->u.ind.t = t->u.info;
    706   t->u.ind.idx = luaK_exp2RK(fs, k);
    707   t->u.ind.vt = (t->k == VUPVAL) ? VUPVAL
    708                                  : check_exp(vkisinreg(t->k), VLOCAL);
    709   t->k = VINDEXED;
    710 }
    711 
    712 
    713 static int constfolding (OpCode op, expdesc *e1, expdesc *e2) {
    714   lua_Number r;
    715   if (!isnumeral(e1) || !isnumeral(e2)) return 0;
    716   if ((op == OP_DIV || op == OP_MOD) && e2->u.nval == 0)
    717     return 0;  /* do not attempt to divide by 0 */
    718   r = luaO_arith(op - OP_ADD + LUA_OPADD, e1->u.nval, e2->u.nval);
    719   e1->u.nval = r;
    720   return 1;
    721 }
    722 
    723 
    724 static void codearith (FuncState *fs, OpCode op,
    725                        expdesc *e1, expdesc *e2, int line) {
    726   if (constfolding(op, e1, e2))
    727     return;
    728   else {
    729     int o2 = (op != OP_UNM && op != OP_LEN) ? luaK_exp2RK(fs, e2) : 0;
    730     int o1 = luaK_exp2RK(fs, e1);
    731     if (o1 > o2) {
    732       freeexp(fs, e1);
    733       freeexp(fs, e2);
    734     }
    735     else {
    736       freeexp(fs, e2);
    737       freeexp(fs, e1);
    738     }
    739     e1->u.info = luaK_codeABC(fs, op, 0, o1, o2);
    740     e1->k = VRELOCABLE;
    741     luaK_fixline(fs, line);
    742   }
    743 }
    744 
    745 
    746 static void codecomp (FuncState *fs, OpCode op, int cond, expdesc *e1,
    747                                                           expdesc *e2) {
    748   int o1 = luaK_exp2RK(fs, e1);
    749   int o2 = luaK_exp2RK(fs, e2);
    750   freeexp(fs, e2);
    751   freeexp(fs, e1);
    752   if (cond == 0 && op != OP_EQ) {
    753     int temp;  /* exchange args to replace by `<' or `<=' */
    754     temp = o1; o1 = o2; o2 = temp;  /* o1 <==> o2 */
    755     cond = 1;
    756   }
    757   e1->u.info = condjump(fs, op, cond, o1, o2);
    758   e1->k = VJMP;
    759 }
    760 
    761 
    762 void luaK_prefix (FuncState *fs, UnOpr op, expdesc *e, int line) {
    763   expdesc e2;
    764   e2.t = e2.f = NO_JUMP; e2.k = VKNUM; e2.u.nval = 0;
    765   switch (op) {
    766     case OPR_MINUS: {
    767       if (isnumeral(e))  /* minus constant? */
    768         e->u.nval = luai_numunm(NULL, e->u.nval);  /* fold it */
    769       else {
    770         luaK_exp2anyreg(fs, e);
    771         codearith(fs, OP_UNM, e, &e2, line);
    772       }
    773       break;
    774     }
    775     case OPR_NOT: codenot(fs, e); break;
    776     case OPR_LEN: {
    777       luaK_exp2anyreg(fs, e);  /* cannot operate on constants */
    778       codearith(fs, OP_LEN, e, &e2, line);
    779       break;
    780     }
    781     default: lua_assert(0);
    782   }
    783 }
    784 
    785 
    786 void luaK_infix (FuncState *fs, BinOpr op, expdesc *v) {
    787   switch (op) {
    788     case OPR_AND: {
    789       luaK_goiftrue(fs, v);
    790       break;
    791     }
    792     case OPR_OR: {
    793       luaK_goiffalse(fs, v);
    794       break;
    795     }
    796     case OPR_CONCAT: {
    797       luaK_exp2nextreg(fs, v);  /* operand must be on the `stack' */
    798       break;
    799     }
    800     case OPR_ADD: case OPR_SUB: case OPR_MUL: case OPR_DIV:
    801     case OPR_MOD: case OPR_POW: {
    802       if (!isnumeral(v)) luaK_exp2RK(fs, v);
    803       break;
    804     }
    805     default: {
    806       luaK_exp2RK(fs, v);
    807       break;
    808     }
    809   }
    810 }
    811 
    812 
    813 void luaK_posfix (FuncState *fs, BinOpr op,
    814                   expdesc *e1, expdesc *e2, int line) {
    815   switch (op) {
    816     case OPR_AND: {
    817       lua_assert(e1->t == NO_JUMP);  /* list must be closed */
    818       luaK_dischargevars(fs, e2);
    819       luaK_concat(fs, &e2->f, e1->f);
    820       *e1 = *e2;
    821       break;
    822     }
    823     case OPR_OR: {
    824       lua_assert(e1->f == NO_JUMP);  /* list must be closed */
    825       luaK_dischargevars(fs, e2);
    826       luaK_concat(fs, &e2->t, e1->t);
    827       *e1 = *e2;
    828       break;
    829     }
    830     case OPR_CONCAT: {
    831       luaK_exp2val(fs, e2);
    832       if (e2->k == VRELOCABLE && GET_OPCODE(getcode(fs, e2)) == OP_CONCAT) {
    833         lua_assert(e1->u.info == GETARG_B(getcode(fs, e2))-1);
    834         freeexp(fs, e1);
    835         SETARG_B(getcode(fs, e2), e1->u.info);
    836         e1->k = VRELOCABLE; e1->u.info = e2->u.info;
    837       }
    838       else {
    839         luaK_exp2nextreg(fs, e2);  /* operand must be on the 'stack' */
    840         codearith(fs, OP_CONCAT, e1, e2, line);
    841       }
    842       break;
    843     }
    844     case OPR_ADD: case OPR_SUB: case OPR_MUL: case OPR_DIV:
    845     case OPR_MOD: case OPR_POW: {
    846       codearith(fs, cast(OpCode, op - OPR_ADD + OP_ADD), e1, e2, line);
    847       break;
    848     }
    849     case OPR_EQ: case OPR_LT: case OPR_LE: {
    850       codecomp(fs, cast(OpCode, op - OPR_EQ + OP_EQ), 1, e1, e2);
    851       break;
    852     }
    853     case OPR_NE: case OPR_GT: case OPR_GE: {
    854       codecomp(fs, cast(OpCode, op - OPR_NE + OP_EQ), 0, e1, e2);
    855       break;
    856     }
    857     default: lua_assert(0);
    858   }
    859 }
    860 
    861 
    862 void luaK_fixline (FuncState *fs, int line) {
    863   fs->f->lineinfo[fs->pc - 1] = line;
    864 }
    865 
    866 
    867 void luaK_setlist (FuncState *fs, int base, int nelems, int tostore) {
    868   int c =  (nelems - 1)/LFIELDS_PER_FLUSH + 1;
    869   int b = (tostore == LUA_MULTRET) ? 0 : tostore;
    870   lua_assert(tostore != 0);
    871   if (c <= MAXARG_C)
    872     luaK_codeABC(fs, OP_SETLIST, base, b, c);
    873   else if (c <= MAXARG_Ax) {
    874     luaK_codeABC(fs, OP_SETLIST, base, b, 0);
    875     codeextraarg(fs, c);
    876   }
    877   else
    878     luaX_syntaxerror(fs->ls, "constructor too long");
    879   fs->freereg = base + 1;  /* free registers with list values */
    880 }
    881 
    882