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  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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.  
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. */
  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. ** Apply prefix operation 'op' to expression 'e'.
  1065. */
  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. */
  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. */
  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. */
  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. */
  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.