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  1. /*
  2. ** $Id: lcode.c $
  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 <float.h>
  14. #include <limits.h>
  15. #include <math.h>
  16. #include <stdlib.h>
  17.  
  18. #include "lua.h"
  19.  
  20. #include "lcode.h"
  21. #include "ldebug.h"
  22. #include "ldo.h"
  23. #include "lgc.h"
  24. #include "llex.h"
  25. #include "lmem.h"
  26. #include "lobject.h"
  27. #include "lopcodes.h"
  28. #include "lparser.h"
  29. #include "lstring.h"
  30. #include "ltable.h"
  31. #include "lvm.h"
  32.  
  33.  
  34. /* Maximum number of registers in a Lua function (must fit in 8 bits) */
  35. #define MAXREGS         255
  36.  
  37.  
  38. #define hasjumps(e)     ((e)->t != (e)->f)
  39.  
  40.  
  41. static int codesJ (FuncState *fs, OpCode o, int sj, int k);
  42.  
  43.  
  44.  
  45. /* semantic error */
  46. l_noret luaK_semerror (LexState *ls, const char *msg) {
  47.   ls->t.token = 0;  /* remove "near <token>" from final message */
  48.   luaX_syntaxerror(ls, msg);
  49. }
  50.  
  51.  
  52. /*
  53. ** If expression is a numeric constant, fills 'v' with its value
  54. ** and returns 1. Otherwise, returns 0.
  55. */
  56. static int tonumeral (const expdesc *e, TValue *v) {
  57.   if (hasjumps(e))
  58.     return 0;  /* not a numeral */
  59.   switch (e->k) {
  60.     case VKINT:
  61.       if (v) setivalue(v, e->u.ival);
  62.       return 1;
  63.     case VKFLT:
  64.       if (v) setfltvalue(v, e->u.nval);
  65.       return 1;
  66.     default: return 0;
  67.   }
  68. }
  69.  
  70.  
  71. /*
  72. ** Get the constant value from a constant expression
  73. */
  74. static TValue *const2val (FuncState *fs, const expdesc *e) {
  75.   lua_assert(e->k == VCONST);
  76.   return &fs->ls->dyd->actvar.arr[e->u.info].k;
  77. }
  78.  
  79.  
  80. /*
  81. ** If expression is a constant, fills 'v' with its value
  82. ** and returns 1. Otherwise, returns 0.
  83. */
  84. int luaK_exp2const (FuncState *fs, const expdesc *e, TValue *v) {
  85.   if (hasjumps(e))
  86.     return 0;  /* not a constant */
  87.   switch (e->k) {
  88.     case VFALSE:
  89.       setbfvalue(v);
  90.       return 1;
  91.     case VTRUE:
  92.       setbtvalue(v);
  93.       return 1;
  94.     case VNIL:
  95.       setnilvalue(v);
  96.       return 1;
  97.     case VKSTR: {
  98.       setsvalue(fs->ls->L, v, e->u.strval);
  99.       return 1;
  100.     }
  101.     case VCONST: {
  102.       setobj(fs->ls->L, v, const2val(fs, e));
  103.       return 1;
  104.     }
  105.     default: return tonumeral(e, v);
  106.   }
  107. }
  108.  
  109.  
  110. /*
  111. ** Return the previous instruction of the current code. If there
  112. ** may be a jump target between the current instruction and the
  113. ** previous one, return an invalid instruction (to avoid wrong
  114. ** optimizations).
  115. */
  116. static Instruction *previousinstruction (FuncState *fs) {
  117.   static const Instruction invalidinstruction = ~(Instruction)0;
  118.   if (fs->pc > fs->lasttarget)
  119.     return &fs->f->code[fs->pc - 1];  /* previous instruction */
  120.   else
  121.     return cast(Instruction*, &invalidinstruction);
  122. }
  123.  
  124.  
  125. /*
  126. ** Create a OP_LOADNIL instruction, but try to optimize: if the previous
  127. ** instruction is also OP_LOADNIL and ranges are compatible, adjust
  128. ** range of previous instruction instead of emitting a new one. (For
  129. ** instance, 'local a; local b' will generate a single opcode.)
  130. */
  131. void luaK_nil (FuncState *fs, int from, int n) {
  132.   int l = from + n - 1;  /* last register to set nil */
  133.   Instruction *previous = previousinstruction(fs);
  134.   if (GET_OPCODE(*previous) == OP_LOADNIL) {  /* previous is LOADNIL? */
  135.     int pfrom = GETARG_A(*previous);  /* get previous range */
  136.     int pl = pfrom + GETARG_B(*previous);
  137.     if ((pfrom <= from && from <= pl + 1) ||
  138.         (from <= pfrom && pfrom <= l + 1)) {  /* can connect both? */
  139.       if (pfrom < from) from = pfrom;  /* from = min(from, pfrom) */
  140.       if (pl > l) l = pl;  /* l = max(l, pl) */
  141.       SETARG_A(*previous, from);
  142.       SETARG_B(*previous, l - from);
  143.       return;
  144.     }  /* else go through */
  145.   }
  146.   luaK_codeABC(fs, OP_LOADNIL, from, n - 1, 0);  /* else no optimization */
  147. }
  148.  
  149.  
  150. /*
  151. ** Gets the destination address of a jump instruction. Used to traverse
  152. ** a list of jumps.
  153. */
  154. static int getjump (FuncState *fs, int pc) {
  155.   int offset = GETARG_sJ(fs->f->code[pc]);
  156.   if (offset == NO_JUMP)  /* point to itself represents end of list */
  157.     return NO_JUMP;  /* end of list */
  158.   else
  159.     return (pc+1)+offset;  /* turn offset into absolute position */
  160. }
  161.  
  162.  
  163. /*
  164. ** Fix jump instruction at position 'pc' to jump to 'dest'.
  165. ** (Jump addresses are relative in Lua)
  166. */
  167. static void fixjump (FuncState *fs, int pc, int dest) {
  168.   Instruction *jmp = &fs->f->code[pc];
  169.   int offset = dest - (pc + 1);
  170.   lua_assert(dest != NO_JUMP);
  171.   if (!(-OFFSET_sJ <= offset && offset <= MAXARG_sJ - OFFSET_sJ))
  172.     luaX_syntaxerror(fs->ls, "control structure too long");
  173.   lua_assert(GET_OPCODE(*jmp) == OP_JMP);
  174.   SETARG_sJ(*jmp, offset);
  175. }
  176.  
  177.  
  178. /*
  179. ** Concatenate jump-list 'l2' into jump-list 'l1'
  180. */
  181. void luaK_concat (FuncState *fs, int *l1, int l2) {
  182.   if (l2 == NO_JUMP) return;  /* nothing to concatenate? */
  183.   else if (*l1 == NO_JUMP)  /* no original list? */
  184.     *l1 = l2;  /* 'l1' points to 'l2' */
  185.   else {
  186.     int list = *l1;
  187.     int next;
  188.     while ((next = getjump(fs, list)) != NO_JUMP)  /* find last element */
  189.       list = next;
  190.     fixjump(fs, list, l2);  /* last element links to 'l2' */
  191.   }
  192. }
  193.  
  194.  
  195. /*
  196. ** Create a jump instruction and return its position, so its destination
  197. ** can be fixed later (with 'fixjump').
  198. */
  199. int luaK_jump (FuncState *fs) {
  200.   return codesJ(fs, OP_JMP, NO_JUMP, 0);
  201. }
  202.  
  203.  
  204. /*
  205. ** Code a 'return' instruction
  206. */
  207. void luaK_ret (FuncState *fs, int first, int nret) {
  208.   OpCode op;
  209.   switch (nret) {
  210.     case 0: op = OP_RETURN0; break;
  211.     case 1: op = OP_RETURN1; break;
  212.     default: op = OP_RETURN; break;
  213.   }
  214.   luaK_codeABC(fs, op, first, nret + 1, 0);
  215. }
  216.  
  217.  
  218. /*
  219. ** Code a "conditional jump", that is, a test or comparison opcode
  220. ** followed by a jump. Return jump position.
  221. */
  222. static int condjump (FuncState *fs, OpCode op, int A, int B, int C, int k) {
  223.   luaK_codeABCk(fs, op, A, B, C, k);
  224.   return luaK_jump(fs);
  225. }
  226.  
  227.  
  228. /*
  229. ** returns current 'pc' and marks it as a jump target (to avoid wrong
  230. ** optimizations with consecutive instructions not in the same basic block).
  231. */
  232. int luaK_getlabel (FuncState *fs) {
  233.   fs->lasttarget = fs->pc;
  234.   return fs->pc;
  235. }
  236.  
  237.  
  238. /*
  239. ** Returns the position of the instruction "controlling" a given
  240. ** jump (that is, its condition), or the jump itself if it is
  241. ** unconditional.
  242. */
  243. static Instruction *getjumpcontrol (FuncState *fs, int pc) {
  244.   Instruction *pi = &fs->f->code[pc];
  245.   if (pc >= 1 && testTMode(GET_OPCODE(*(pi-1))))
  246.     return pi-1;
  247.   else
  248.     return pi;
  249. }
  250.  
  251.  
  252. /*
  253. ** Patch destination register for a TESTSET instruction.
  254. ** If instruction in position 'node' is not a TESTSET, return 0 ("fails").
  255. ** Otherwise, if 'reg' is not 'NO_REG', set it as the destination
  256. ** register. Otherwise, change instruction to a simple 'TEST' (produces
  257. ** no register value)
  258. */
  259. static int patchtestreg (FuncState *fs, int node, int reg) {
  260.   Instruction *i = getjumpcontrol(fs, node);
  261.   if (GET_OPCODE(*i) != OP_TESTSET)
  262.     return 0;  /* cannot patch other instructions */
  263.   if (reg != NO_REG && reg != GETARG_B(*i))
  264.     SETARG_A(*i, reg);
  265.   else {
  266.      /* no register to put value or register already has the value;
  267.         change instruction to simple test */
  268.     *i = CREATE_ABCk(OP_TEST, GETARG_B(*i), 0, 0, GETARG_k(*i));
  269.   }
  270.   return 1;
  271. }
  272.  
  273.  
  274. /*
  275. ** Traverse a list of tests ensuring no one produces a value
  276. */
  277. static void removevalues (FuncState *fs, int list) {
  278.   for (; list != NO_JUMP; list = getjump(fs, list))
  279.       patchtestreg(fs, list, NO_REG);
  280. }
  281.  
  282.  
  283. /*
  284. ** Traverse a list of tests, patching their destination address and
  285. ** registers: tests producing values jump to 'vtarget' (and put their
  286. ** values in 'reg'), other tests jump to 'dtarget'.
  287. */
  288. static void patchlistaux (FuncState *fs, int list, int vtarget, int reg,
  289.                           int dtarget) {
  290.   while (list != NO_JUMP) {
  291.     int next = getjump(fs, list);
  292.     if (patchtestreg(fs, list, reg))
  293.       fixjump(fs, list, vtarget);
  294.     else
  295.       fixjump(fs, list, dtarget);  /* jump to default target */
  296.     list = next;
  297.   }
  298. }
  299.  
  300.  
  301. /*
  302. ** Path all jumps in 'list' to jump to 'target'.
  303. ** (The assert means that we cannot fix a jump to a forward address
  304. ** because we only know addresses once code is generated.)
  305. */
  306. void luaK_patchlist (FuncState *fs, int list, int target) {
  307.   lua_assert(target <= fs->pc);
  308.   patchlistaux(fs, list, target, NO_REG, target);
  309. }
  310.  
  311.  
  312. void luaK_patchtohere (FuncState *fs, int list) {
  313.   int hr = luaK_getlabel(fs);  /* mark "here" as a jump target */
  314.   luaK_patchlist(fs, list, hr);
  315. }
  316.  
  317.  
  318. /* limit for difference between lines in relative line info. */
  319. #define LIMLINEDIFF     0x80
  320.  
  321.  
  322. /*
  323. ** Save line info for a new instruction. If difference from last line
  324. ** does not fit in a byte, of after that many instructions, save a new
  325. ** absolute line info; (in that case, the special value 'ABSLINEINFO'
  326. ** in 'lineinfo' signals the existence of this absolute information.)
  327. ** Otherwise, store the difference from last line in 'lineinfo'.
  328. */
  329. static void savelineinfo (FuncState *fs, Proto *f, int line) {
  330.   int linedif = line - fs->previousline;
  331.   int pc = fs->pc - 1;  /* last instruction coded */
  332.   if (abs(linedif) >= LIMLINEDIFF || fs->iwthabs++ >= MAXIWTHABS) {
  333.     luaM_growvector(fs->ls->L, f->abslineinfo, fs->nabslineinfo,
  334.                     f->sizeabslineinfo, AbsLineInfo, MAX_INT, "lines");
  335.     f->abslineinfo[fs->nabslineinfo].pc = pc;
  336.     f->abslineinfo[fs->nabslineinfo++].line = line;
  337.     linedif = ABSLINEINFO;  /* signal that there is absolute information */
  338.     fs->iwthabs = 1;  /* restart counter */
  339.   }
  340.   luaM_growvector(fs->ls->L, f->lineinfo, pc, f->sizelineinfo, ls_byte,
  341.                   MAX_INT, "opcodes");
  342.   f->lineinfo[pc] = linedif;
  343.   fs->previousline = line;  /* last line saved */
  344. }
  345.  
  346.  
  347. /*
  348. ** Remove line information from the last instruction.
  349. ** If line information for that instruction is absolute, set 'iwthabs'
  350. ** above its max to force the new (replacing) instruction to have
  351. ** absolute line info, too.
  352. */
  353. static void removelastlineinfo (FuncState *fs) {
  354.   Proto *f = fs->f;
  355.   int pc = fs->pc - 1;  /* last instruction coded */
  356.   if (f->lineinfo[pc] != ABSLINEINFO) {  /* relative line info? */
  357.     fs->previousline -= f->lineinfo[pc];  /* correct last line saved */
  358.     fs->iwthabs--;  /* undo previous increment */
  359.   }
  360.   else {  /* absolute line information */
  361.     lua_assert(f->abslineinfo[fs->nabslineinfo - 1].pc == pc);
  362.     fs->nabslineinfo--;  /* remove it */
  363.     fs->iwthabs = MAXIWTHABS + 1;  /* force next line info to be absolute */
  364.   }
  365. }
  366.  
  367.  
  368. /*
  369. ** Remove the last instruction created, correcting line information
  370. ** accordingly.
  371. */
  372. static void removelastinstruction (FuncState *fs) {
  373.   removelastlineinfo(fs);
  374.   fs->pc--;
  375. }
  376.  
  377.  
  378. /*
  379. ** Emit instruction 'i', checking for array sizes and saving also its
  380. ** line information. Return 'i' position.
  381. */
  382. int luaK_code (FuncState *fs, Instruction i) {
  383.   Proto *f = fs->f;
  384.   /* put new instruction in code array */
  385.   luaM_growvector(fs->ls->L, f->code, fs->pc, f->sizecode, Instruction,
  386.                   MAX_INT, "opcodes");
  387.   f->code[fs->pc++] = i;
  388.   savelineinfo(fs, f, fs->ls->lastline);
  389.   return fs->pc - 1;  /* index of new instruction */
  390. }
  391.  
  392.  
  393. /*
  394. ** Format and emit an 'iABC' instruction. (Assertions check consistency
  395. ** of parameters versus opcode.)
  396. */
  397. int luaK_codeABCk (FuncState *fs, OpCode o, int a, int b, int c, int k) {
  398.   lua_assert(getOpMode(o) == iABC);
  399.   lua_assert(a <= MAXARG_A && b <= MAXARG_B &&
  400.              c <= MAXARG_C && (k & ~1) == 0);
  401.   return luaK_code(fs, CREATE_ABCk(o, a, b, c, k));
  402. }
  403.  
  404.  
  405. /*
  406. ** Format and emit an 'iABx' instruction.
  407. */
  408. int luaK_codeABx (FuncState *fs, OpCode o, int a, unsigned int bc) {
  409.   lua_assert(getOpMode(o) == iABx);
  410.   lua_assert(a <= MAXARG_A && bc <= MAXARG_Bx);
  411.   return luaK_code(fs, CREATE_ABx(o, a, bc));
  412. }
  413.  
  414.  
  415. /*
  416. ** Format and emit an 'iAsBx' instruction.
  417. */
  418. int luaK_codeAsBx (FuncState *fs, OpCode o, int a, int bc) {
  419.   unsigned int b = bc + OFFSET_sBx;
  420.   lua_assert(getOpMode(o) == iAsBx);
  421.   lua_assert(a <= MAXARG_A && b <= MAXARG_Bx);
  422.   return luaK_code(fs, CREATE_ABx(o, a, b));
  423. }
  424.  
  425.  
  426. /*
  427. ** Format and emit an 'isJ' instruction.
  428. */
  429. static int codesJ (FuncState *fs, OpCode o, int sj, int k) {
  430.   unsigned int j = sj + OFFSET_sJ;
  431.   lua_assert(getOpMode(o) == isJ);
  432.   lua_assert(j <= MAXARG_sJ && (k & ~1) == 0);
  433.   return luaK_code(fs, CREATE_sJ(o, j, k));
  434. }
  435.  
  436.  
  437. /*
  438. ** Emit an "extra argument" instruction (format 'iAx')
  439. */
  440. static int codeextraarg (FuncState *fs, int a) {
  441.   lua_assert(a <= MAXARG_Ax);
  442.   return luaK_code(fs, CREATE_Ax(OP_EXTRAARG, a));
  443. }
  444.  
  445.  
  446. /*
  447. ** Emit a "load constant" instruction, using either 'OP_LOADK'
  448. ** (if constant index 'k' fits in 18 bits) or an 'OP_LOADKX'
  449. ** instruction with "extra argument".
  450. */
  451. static int luaK_codek (FuncState *fs, int reg, int k) {
  452.   if (k <= MAXARG_Bx)
  453.     return luaK_codeABx(fs, OP_LOADK, reg, k);
  454.   else {
  455.     int p = luaK_codeABx(fs, OP_LOADKX, reg, 0);
  456.     codeextraarg(fs, k);
  457.     return p;
  458.   }
  459. }
  460.  
  461.  
  462. /*
  463. ** Check register-stack level, keeping track of its maximum size
  464. ** in field 'maxstacksize'
  465. */
  466. void luaK_checkstack (FuncState *fs, int n) {
  467.   int newstack = fs->freereg + n;
  468.   if (newstack > fs->f->maxstacksize) {
  469.     if (newstack >= MAXREGS)
  470.       luaX_syntaxerror(fs->ls,
  471.         "function or expression needs too many registers");
  472.     fs->f->maxstacksize = cast_byte(newstack);
  473.   }
  474. }
  475.  
  476.  
  477. /*
  478. ** Reserve 'n' registers in register stack
  479. */
  480. void luaK_reserveregs (FuncState *fs, int n) {
  481.   luaK_checkstack(fs, n);
  482.   fs->freereg += n;
  483. }
  484.  
  485.  
  486. /*
  487. ** Free register 'reg', if it is neither a constant index nor
  488. ** a local variable.
  489. )
  490. */
  491. static void freereg (FuncState *fs, int reg) {
  492.   if (reg >= luaY_nvarstack(fs)) {
  493.     fs->freereg--;
  494.     lua_assert(reg == fs->freereg);
  495.   }
  496. }
  497.  
  498.  
  499. /*
  500. ** Free two registers in proper order
  501. */
  502. static void freeregs (FuncState *fs, int r1, int r2) {
  503.   if (r1 > r2) {
  504.     freereg(fs, r1);
  505.     freereg(fs, r2);
  506.   }
  507.   else {
  508.     freereg(fs, r2);
  509.     freereg(fs, r1);
  510.   }
  511. }
  512.  
  513.  
  514. /*
  515. ** Free register used by expression 'e' (if any)
  516. */
  517. static void freeexp (FuncState *fs, expdesc *e) {
  518.   if (e->k == VNONRELOC)
  519.     freereg(fs, e->u.info);
  520. }
  521.  
  522.  
  523. /*
  524. ** Free registers used by expressions 'e1' and 'e2' (if any) in proper
  525. ** order.
  526. */
  527. static void freeexps (FuncState *fs, expdesc *e1, expdesc *e2) {
  528.   int r1 = (e1->k == VNONRELOC) ? e1->u.info : -1;
  529.   int r2 = (e2->k == VNONRELOC) ? e2->u.info : -1;
  530.   freeregs(fs, r1, r2);
  531. }
  532.  
  533.  
  534. /*
  535. ** Add constant 'v' to prototype's list of constants (field 'k').
  536. ** Use scanner's table to cache position of constants in constant list
  537. ** and try to reuse constants. Because some values should not be used
  538. ** as keys (nil cannot be a key, integer keys can collapse with float
  539. ** keys), the caller must provide a useful 'key' for indexing the cache.
  540. ** Note that all functions share the same table, so entering or exiting
  541. ** a function can make some indices wrong.
  542. */
  543. static int addk (FuncState *fs, TValue *key, TValue *v) {
  544.   TValue val;
  545.   lua_State *L = fs->ls->L;
  546.   Proto *f = fs->f;
  547.   const TValue *idx = luaH_get(fs->ls->h, key);  /* query scanner table */
  548.   int k, oldsize;
  549.   if (ttisinteger(idx)) {  /* is there an index there? */
  550.     k = cast_int(ivalue(idx));
  551.     /* correct value? (warning: must distinguish floats from integers!) */
  552.     if (k < fs->nk && ttypetag(&f->k[k]) == ttypetag(v) &&
  553.                       luaV_rawequalobj(&f->k[k], v))
  554.       return k;  /* reuse index */
  555.   }
  556.   /* constant not found; create a new entry */
  557.   oldsize = f->sizek;
  558.   k = fs->nk;
  559.   /* numerical value does not need GC barrier;
  560.      table has no metatable, so it does not need to invalidate cache */
  561.   setivalue(&val, k);
  562.   luaH_finishset(L, fs->ls->h, key, idx, &val);
  563.   luaM_growvector(L, f->k, k, f->sizek, TValue, MAXARG_Ax, "constants");
  564.   while (oldsize < f->sizek) setnilvalue(&f->k[oldsize++]);
  565.   setobj(L, &f->k[k], v);
  566.   fs->nk++;
  567.   luaC_barrier(L, f, v);
  568.   return k;
  569. }
  570.  
  571.  
  572. /*
  573. ** Add a string to list of constants and return its index.
  574. */
  575. static int stringK (FuncState *fs, TString *s) {
  576.   TValue o;
  577.   setsvalue(fs->ls->L, &o, s);
  578.   return addk(fs, &o, &o);  /* use string itself as key */
  579. }
  580.  
  581.  
  582. /*
  583. ** Add an integer to list of constants and return its index.
  584. */
  585. static int luaK_intK (FuncState *fs, lua_Integer n) {
  586.   TValue o;
  587.   setivalue(&o, n);
  588.   return addk(fs, &o, &o);  /* use integer itself as key */
  589. }
  590.  
  591. /*
  592. ** Add a float to list of constants and return its index. Floats
  593. ** with integral values need a different key, to avoid collision
  594. ** with actual integers. To that, we add to the number its smaller
  595. ** power-of-two fraction that is still significant in its scale.
  596. ** For doubles, that would be 1/2^52.
  597. ** (This method is not bulletproof: there may be another float
  598. ** with that value, and for floats larger than 2^53 the result is
  599. ** still an integer. At worst, this only wastes an entry with
  600. ** a duplicate.)
  601. */
  602. static int luaK_numberK (FuncState *fs, lua_Number r) {
  603.   TValue o;
  604.   lua_Integer ik;
  605.   setfltvalue(&o, r);
  606.   if (!luaV_flttointeger(r, &ik, F2Ieq))  /* not an integral value? */
  607.     return addk(fs, &o, &o);  /* use number itself as key */
  608.   else {  /* must build an alternative key */
  609.     const int nbm = l_floatatt(MANT_DIG);
  610.     const lua_Number q = l_mathop(ldexp)(l_mathop(1.0), -nbm + 1);
  611.     const lua_Number k = (ik == 0) ? q : r + r*q;  /* new key */
  612.     TValue kv;
  613.     setfltvalue(&kv, k);
  614.     /* result is not an integral value, unless value is too large */
  615.     lua_assert(!luaV_flttointeger(k, &ik, F2Ieq) ||
  616.                 l_mathop(fabs)(r) >= l_mathop(1e6));
  617.     return addk(fs, &kv, &o);
  618.   }
  619. }
  620.  
  621.  
  622. /*
  623. ** Add a false to list of constants and return its index.
  624. */
  625. static int boolF (FuncState *fs) {
  626.   TValue o;
  627.   setbfvalue(&o);
  628.   return addk(fs, &o, &o);  /* use boolean itself as key */
  629. }
  630.  
  631.  
  632. /*
  633. ** Add a true to list of constants and return its index.
  634. */
  635. static int boolT (FuncState *fs) {
  636.   TValue o;
  637.   setbtvalue(&o);
  638.   return addk(fs, &o, &o);  /* use boolean itself as key */
  639. }
  640.  
  641.  
  642. /*
  643. ** Add nil to list of constants and return its index.
  644. */
  645. static int nilK (FuncState *fs) {
  646.   TValue k, v;
  647.   setnilvalue(&v);
  648.   /* cannot use nil as key; instead use table itself to represent nil */
  649.   sethvalue(fs->ls->L, &k, fs->ls->h);
  650.   return addk(fs, &k, &v);
  651. }
  652.  
  653.  
  654. /*
  655. ** Check whether 'i' can be stored in an 'sC' operand. Equivalent to
  656. ** (0 <= int2sC(i) && int2sC(i) <= MAXARG_C) but without risk of
  657. ** overflows in the hidden addition inside 'int2sC'.
  658. */
  659. static int fitsC (lua_Integer i) {
  660.   return (l_castS2U(i) + OFFSET_sC <= cast_uint(MAXARG_C));
  661. }
  662.  
  663.  
  664. /*
  665. ** Check whether 'i' can be stored in an 'sBx' operand.
  666. */
  667. static int fitsBx (lua_Integer i) {
  668.   return (-OFFSET_sBx <= i && i <= MAXARG_Bx - OFFSET_sBx);
  669. }
  670.  
  671.  
  672. void luaK_int (FuncState *fs, int reg, lua_Integer i) {
  673.   if (fitsBx(i))
  674.     luaK_codeAsBx(fs, OP_LOADI, reg, cast_int(i));
  675.   else
  676.     luaK_codek(fs, reg, luaK_intK(fs, i));
  677. }
  678.  
  679.  
  680. static void luaK_float (FuncState *fs, int reg, lua_Number f) {
  681.   lua_Integer fi;
  682.   if (luaV_flttointeger(f, &fi, F2Ieq) && fitsBx(fi))
  683.     luaK_codeAsBx(fs, OP_LOADF, reg, cast_int(fi));
  684.   else
  685.     luaK_codek(fs, reg, luaK_numberK(fs, f));
  686. }
  687.  
  688.  
  689. /*
  690. ** Convert a constant in 'v' into an expression description 'e'
  691. */
  692. static void const2exp (TValue *v, expdesc *e) {
  693.   switch (ttypetag(v)) {
  694.     case LUA_VNUMINT:
  695.       e->k = VKINT; e->u.ival = ivalue(v);
  696.       break;
  697.     case LUA_VNUMFLT:
  698.       e->k = VKFLT; e->u.nval = fltvalue(v);
  699.       break;
  700.     case LUA_VFALSE:
  701.       e->k = VFALSE;
  702.       break;
  703.     case LUA_VTRUE:
  704.       e->k = VTRUE;
  705.       break;
  706.     case LUA_VNIL:
  707.       e->k = VNIL;
  708.       break;
  709.     case LUA_VSHRSTR:  case LUA_VLNGSTR:
  710.       e->k = VKSTR; e->u.strval = tsvalue(v);
  711.       break;
  712.     default: lua_assert(0);
  713.   }
  714. }
  715.  
  716.  
  717. /*
  718. ** Fix an expression to return the number of results 'nresults'.
  719. ** 'e' must be a multi-ret expression (function call or vararg).
  720. */
  721. void luaK_setreturns (FuncState *fs, expdesc *e, int nresults) {
  722.   Instruction *pc = &getinstruction(fs, e);
  723.   if (e->k == VCALL)  /* expression is an open function call? */
  724.     SETARG_C(*pc, nresults + 1);
  725.   else {
  726.     lua_assert(e->k == VVARARG);
  727.     SETARG_C(*pc, nresults + 1);
  728.     SETARG_A(*pc, fs->freereg);
  729.     luaK_reserveregs(fs, 1);
  730.   }
  731. }
  732.  
  733.  
  734. /*
  735. ** Convert a VKSTR to a VK
  736. */
  737. static void str2K (FuncState *fs, expdesc *e) {
  738.   lua_assert(e->k == VKSTR);
  739.   e->u.info = stringK(fs, e->u.strval);
  740.   e->k = VK;
  741. }
  742.  
  743.  
  744. /*
  745. ** Fix an expression to return one result.
  746. ** If expression is not a multi-ret expression (function call or
  747. ** vararg), it already returns one result, so nothing needs to be done.
  748. ** Function calls become VNONRELOC expressions (as its result comes
  749. ** fixed in the base register of the call), while vararg expressions
  750. ** become VRELOC (as OP_VARARG puts its results where it wants).
  751. ** (Calls are created returning one result, so that does not need
  752. ** to be fixed.)
  753. */
  754. void luaK_setoneret (FuncState *fs, expdesc *e) {
  755.   if (e->k == VCALL) {  /* expression is an open function call? */
  756.     /* already returns 1 value */
  757.     lua_assert(GETARG_C(getinstruction(fs, e)) == 2);
  758.     e->k = VNONRELOC;  /* result has fixed position */
  759.     e->u.info = GETARG_A(getinstruction(fs, e));
  760.   }
  761.   else if (e->k == VVARARG) {
  762.     SETARG_C(getinstruction(fs, e), 2);
  763.     e->k = VRELOC;  /* can relocate its simple result */
  764.   }
  765. }
  766.  
  767.  
  768. /*
  769. ** Ensure that expression 'e' is not a variable (nor a <const>).
  770. ** (Expression still may have jump lists.)
  771. */
  772. void luaK_dischargevars (FuncState *fs, expdesc *e) {
  773.   switch (e->k) {
  774.     case VCONST: {
  775.       const2exp(const2val(fs, e), e);
  776.       break;
  777.     }
  778.     case VLOCAL: {  /* already in a register */
  779.       e->u.info = e->u.var.ridx;
  780.       e->k = VNONRELOC;  /* becomes a non-relocatable value */
  781.       break;
  782.     }
  783.     case VUPVAL: {  /* move value to some (pending) register */
  784.       e->u.info = luaK_codeABC(fs, OP_GETUPVAL, 0, e->u.info, 0);
  785.       e->k = VRELOC;
  786.       break;
  787.     }
  788.     case VINDEXUP: {
  789.       e->u.info = luaK_codeABC(fs, OP_GETTABUP, 0, e->u.ind.t, e->u.ind.idx);
  790.       e->k = VRELOC;
  791.       break;
  792.     }
  793.     case VINDEXI: {
  794.       freereg(fs, e->u.ind.t);
  795.       e->u.info = luaK_codeABC(fs, OP_GETI, 0, e->u.ind.t, e->u.ind.idx);
  796.       e->k = VRELOC;
  797.       break;
  798.     }
  799.     case VINDEXSTR: {
  800.       freereg(fs, e->u.ind.t);
  801.       e->u.info = luaK_codeABC(fs, OP_GETFIELD, 0, e->u.ind.t, e->u.ind.idx);
  802.       e->k = VRELOC;
  803.       break;
  804.     }
  805.     case VINDEXED: {
  806.       freeregs(fs, e->u.ind.t, e->u.ind.idx);
  807.       e->u.info = luaK_codeABC(fs, OP_GETTABLE, 0, e->u.ind.t, e->u.ind.idx);
  808.       e->k = VRELOC;
  809.       break;
  810.     }
  811.     case VVARARG: case VCALL: {
  812.       luaK_setoneret(fs, e);
  813.       break;
  814.     }
  815.     default: break;  /* there is one value available (somewhere) */
  816.   }
  817. }
  818.  
  819.  
  820. /*
  821. ** Ensure expression value is in register 'reg', making 'e' a
  822. ** non-relocatable expression.
  823. ** (Expression still may have jump lists.)
  824. */
  825. static void discharge2reg (FuncState *fs, expdesc *e, int reg) {
  826.   luaK_dischargevars(fs, e);
  827.   switch (e->k) {
  828.     case VNIL: {
  829.       luaK_nil(fs, reg, 1);
  830.       break;
  831.     }
  832.     case VFALSE: {
  833.       luaK_codeABC(fs, OP_LOADFALSE, reg, 0, 0);
  834.       break;
  835.     }
  836.     case VTRUE: {
  837.       luaK_codeABC(fs, OP_LOADTRUE, reg, 0, 0);
  838.       break;
  839.     }
  840.     case VKSTR: {
  841.       str2K(fs, e);
  842.     }  /* FALLTHROUGH */
  843.     case VK: {
  844.       luaK_codek(fs, reg, e->u.info);
  845.       break;
  846.     }
  847.     case VKFLT: {
  848.       luaK_float(fs, reg, e->u.nval);
  849.       break;
  850.     }
  851.     case VKINT: {
  852.       luaK_int(fs, reg, e->u.ival);
  853.       break;
  854.     }
  855.     case VRELOC: {
  856.       Instruction *pc = &getinstruction(fs, e);
  857.       SETARG_A(*pc, reg);  /* instruction will put result in 'reg' */
  858.       break;
  859.     }
  860.     case VNONRELOC: {
  861.       if (reg != e->u.info)
  862.         luaK_codeABC(fs, OP_MOVE, reg, e->u.info, 0);
  863.       break;
  864.     }
  865.     default: {
  866.       lua_assert(e->k == VJMP);
  867.       return;  /* nothing to do... */
  868.     }
  869.   }
  870.   e->u.info = reg;
  871.   e->k = VNONRELOC;
  872. }
  873.  
  874.  
  875. /*
  876. ** Ensure expression value is in a register, making 'e' a
  877. ** non-relocatable expression.
  878. ** (Expression still may have jump lists.)
  879. */
  880. static void discharge2anyreg (FuncState *fs, expdesc *e) {
  881.   if (e->k != VNONRELOC) {  /* no fixed register yet? */
  882.     luaK_reserveregs(fs, 1);  /* get a register */
  883.     discharge2reg(fs, e, fs->freereg-1);  /* put value there */
  884.   }
  885. }
  886.  
  887.  
  888. static int code_loadbool (FuncState *fs, int A, OpCode op) {
  889.   luaK_getlabel(fs);  /* those instructions may be jump targets */
  890.   return luaK_codeABC(fs, op, A, 0, 0);
  891. }
  892.  
  893.  
  894. /*
  895. ** check whether list has any jump that do not produce a value
  896. ** or produce an inverted value
  897. */
  898. static int need_value (FuncState *fs, int list) {
  899.   for (; list != NO_JUMP; list = getjump(fs, list)) {
  900.     Instruction i = *getjumpcontrol(fs, list);
  901.     if (GET_OPCODE(i) != OP_TESTSET) return 1;
  902.   }
  903.   return 0;  /* not found */
  904. }
  905.  
  906.  
  907. /*
  908. ** Ensures final expression result (which includes results from its
  909. ** jump lists) is in register 'reg'.
  910. ** If expression has jumps, need to patch these jumps either to
  911. ** its final position or to "load" instructions (for those tests
  912. ** that do not produce values).
  913. */
  914. static void exp2reg (FuncState *fs, expdesc *e, int reg) {
  915.   discharge2reg(fs, e, reg);
  916.   if (e->k == VJMP)  /* expression itself is a test? */
  917.     luaK_concat(fs, &e->t, e->u.info);  /* put this jump in 't' list */
  918.   if (hasjumps(e)) {
  919.     int final;  /* position after whole expression */
  920.     int p_f = NO_JUMP;  /* position of an eventual LOAD false */
  921.     int p_t = NO_JUMP;  /* position of an eventual LOAD true */
  922.     if (need_value(fs, e->t) || need_value(fs, e->f)) {
  923.       int fj = (e->k == VJMP) ? NO_JUMP : luaK_jump(fs);
  924.       p_f = code_loadbool(fs, reg, OP_LFALSESKIP);  /* skip next inst. */
  925.       p_t = code_loadbool(fs, reg, OP_LOADTRUE);
  926.       /* jump around these booleans if 'e' is not a test */
  927.       luaK_patchtohere(fs, fj);
  928.     }
  929.     final = luaK_getlabel(fs);
  930.     patchlistaux(fs, e->f, final, reg, p_f);
  931.     patchlistaux(fs, e->t, final, reg, p_t);
  932.   }
  933.   e->f = e->t = NO_JUMP;
  934.   e->u.info = reg;
  935.   e->k = VNONRELOC;
  936. }
  937.  
  938.  
  939. /*
  940. ** Ensures final expression result is in next available register.
  941. */
  942. void luaK_exp2nextreg (FuncState *fs, expdesc *e) {
  943.   luaK_dischargevars(fs, e);
  944.   freeexp(fs, e);
  945.   luaK_reserveregs(fs, 1);
  946.   exp2reg(fs, e, fs->freereg - 1);
  947. }
  948.  
  949.  
  950. /*
  951. ** Ensures final expression result is in some (any) register
  952. ** and return that register.
  953. */
  954. int luaK_exp2anyreg (FuncState *fs, expdesc *e) {
  955.   luaK_dischargevars(fs, e);
  956.   if (e->k == VNONRELOC) {  /* expression already has a register? */
  957.     if (!hasjumps(e))  /* no jumps? */
  958.       return e->u.info;  /* result is already in a register */
  959.     if (e->u.info >= luaY_nvarstack(fs)) {  /* reg. is not a local? */
  960.       exp2reg(fs, e, e->u.info);  /* put final result in it */
  961.       return e->u.info;
  962.     }
  963.     /* else expression has jumps and cannot change its register
  964.        to hold the jump values, because it is a local variable.
  965.        Go through to the default case. */
  966.   }
  967.   luaK_exp2nextreg(fs, e);  /* default: use next available register */
  968.   return e->u.info;
  969. }
  970.  
  971.  
  972. /*
  973. ** Ensures final expression result is either in a register
  974. ** or in an upvalue.
  975. */
  976. void luaK_exp2anyregup (FuncState *fs, expdesc *e) {
  977.   if (e->k != VUPVAL || hasjumps(e))
  978.     luaK_exp2anyreg(fs, e);
  979. }
  980.  
  981.  
  982. /*
  983. ** Ensures final expression result is either in a register
  984. ** or it is a constant.
  985. */
  986. void luaK_exp2val (FuncState *fs, expdesc *e) {
  987.   if (hasjumps(e))
  988.     luaK_exp2anyreg(fs, e);
  989.   else
  990.     luaK_dischargevars(fs, e);
  991. }
  992.  
  993.  
  994. /*
  995. ** Try to make 'e' a K expression with an index in the range of R/K
  996. ** indices. Return true iff succeeded.
  997. */
  998. static int luaK_exp2K (FuncState *fs, expdesc *e) {
  999.   if (!hasjumps(e)) {
  1000.     int info;
  1001.     switch (e->k) {  /* move constants to 'k' */
  1002.       case VTRUE: info = boolT(fs); break;
  1003.       case VFALSE: info = boolF(fs); break;
  1004.       case VNIL: info = nilK(fs); break;
  1005.       case VKINT: info = luaK_intK(fs, e->u.ival); break;
  1006.       case VKFLT: info = luaK_numberK(fs, e->u.nval); break;
  1007.       case VKSTR: info = stringK(fs, e->u.strval); break;
  1008.       case VK: info = e->u.info; break;
  1009.       default: return 0;  /* not a constant */
  1010.     }
  1011.     if (info <= MAXINDEXRK) {  /* does constant fit in 'argC'? */
  1012.       e->k = VK;  /* make expression a 'K' expression */
  1013.       e->u.info = info;
  1014.       return 1;
  1015.     }
  1016.   }
  1017.   /* else, expression doesn't fit; leave it unchanged */
  1018.   return 0;
  1019. }
  1020.  
  1021.  
  1022. /*
  1023. ** Ensures final expression result is in a valid R/K index
  1024. ** (that is, it is either in a register or in 'k' with an index
  1025. ** in the range of R/K indices).
  1026. ** Returns 1 iff expression is K.
  1027. */
  1028. int luaK_exp2RK (FuncState *fs, expdesc *e) {
  1029.   if (luaK_exp2K(fs, e))
  1030.     return 1;
  1031.   else {  /* not a constant in the right range: put it in a register */
  1032.     luaK_exp2anyreg(fs, e);
  1033.     return 0;
  1034.   }
  1035. }
  1036.  
  1037.  
  1038. static void codeABRK (FuncState *fs, OpCode o, int a, int b,
  1039.                       expdesc *ec) {
  1040.   int k = luaK_exp2RK(fs, ec);
  1041.   luaK_codeABCk(fs, o, a, b, ec->u.info, k);
  1042. }
  1043.  
  1044.  
  1045. /*
  1046. ** Generate code to store result of expression 'ex' into variable 'var'.
  1047. */
  1048. void luaK_storevar (FuncState *fs, expdesc *var, expdesc *ex) {
  1049.   switch (var->k) {
  1050.     case VLOCAL: {
  1051.       freeexp(fs, ex);
  1052.       exp2reg(fs, ex, var->u.var.ridx);  /* compute 'ex' into proper place */
  1053.       return;
  1054.     }
  1055.     case VUPVAL: {
  1056.       int e = luaK_exp2anyreg(fs, ex);
  1057.       luaK_codeABC(fs, OP_SETUPVAL, e, var->u.info, 0);
  1058.       break;
  1059.     }
  1060.     case VINDEXUP: {
  1061.       codeABRK(fs, OP_SETTABUP, var->u.ind.t, var->u.ind.idx, ex);
  1062.       break;
  1063.     }
  1064.     case VINDEXI: {
  1065.       codeABRK(fs, OP_SETI, var->u.ind.t, var->u.ind.idx, ex);
  1066.       break;
  1067.     }
  1068.     case VINDEXSTR: {
  1069.       codeABRK(fs, OP_SETFIELD, var->u.ind.t, var->u.ind.idx, ex);
  1070.       break;
  1071.     }
  1072.     case VINDEXED: {
  1073.       codeABRK(fs, OP_SETTABLE, var->u.ind.t, var->u.ind.idx, ex);
  1074.       break;
  1075.     }
  1076.     default: lua_assert(0);  /* invalid var kind to store */
  1077.   }
  1078.   freeexp(fs, ex);
  1079. }
  1080.  
  1081.  
  1082. /*
  1083. ** Emit SELF instruction (convert expression 'e' into 'e:key(e,').
  1084. */
  1085. void luaK_self (FuncState *fs, expdesc *e, expdesc *key) {
  1086.   int ereg;
  1087.   luaK_exp2anyreg(fs, e);
  1088.   ereg = e->u.info;  /* register where 'e' was placed */
  1089.   freeexp(fs, e);
  1090.   e->u.info = fs->freereg;  /* base register for op_self */
  1091.   e->k = VNONRELOC;  /* self expression has a fixed register */
  1092.   luaK_reserveregs(fs, 2);  /* function and 'self' produced by op_self */
  1093.   codeABRK(fs, OP_SELF, e->u.info, ereg, key);
  1094.   freeexp(fs, key);
  1095. }
  1096.  
  1097.  
  1098. /*
  1099. ** Negate condition 'e' (where 'e' is a comparison).
  1100. */
  1101. static void negatecondition (FuncState *fs, expdesc *e) {
  1102.   Instruction *pc = getjumpcontrol(fs, e->u.info);
  1103.   lua_assert(testTMode(GET_OPCODE(*pc)) && GET_OPCODE(*pc) != OP_TESTSET &&
  1104.                                            GET_OPCODE(*pc) != OP_TEST);
  1105.   SETARG_k(*pc, (GETARG_k(*pc) ^ 1));
  1106. }
  1107.  
  1108.  
  1109. /*
  1110. ** Emit instruction to jump if 'e' is 'cond' (that is, if 'cond'
  1111. ** is true, code will jump if 'e' is true.) Return jump position.
  1112. ** Optimize when 'e' is 'not' something, inverting the condition
  1113. ** and removing the 'not'.
  1114. */
  1115. static int jumponcond (FuncState *fs, expdesc *e, int cond) {
  1116.   if (e->k == VRELOC) {
  1117.     Instruction ie = getinstruction(fs, e);
  1118.     if (GET_OPCODE(ie) == OP_NOT) {
  1119.       removelastinstruction(fs);  /* remove previous OP_NOT */
  1120.       return condjump(fs, OP_TEST, GETARG_B(ie), 0, 0, !cond);
  1121.     }
  1122.     /* else go through */
  1123.   }
  1124.   discharge2anyreg(fs, e);
  1125.   freeexp(fs, e);
  1126.   return condjump(fs, OP_TESTSET, NO_REG, e->u.info, 0, cond);
  1127. }
  1128.  
  1129.  
  1130. /*
  1131. ** Emit code to go through if 'e' is true, jump otherwise.
  1132. */
  1133. void luaK_goiftrue (FuncState *fs, expdesc *e) {
  1134.   int pc;  /* pc of new jump */
  1135.   luaK_dischargevars(fs, e);
  1136.   switch (e->k) {
  1137.     case VJMP: {  /* condition? */
  1138.       negatecondition(fs, e);  /* jump when it is false */
  1139.       pc = e->u.info;  /* save jump position */
  1140.       break;
  1141.     }
  1142.     case VK: case VKFLT: case VKINT: case VKSTR: case VTRUE: {
  1143.       pc = NO_JUMP;  /* always true; do nothing */
  1144.       break;
  1145.     }
  1146.     default: {
  1147.       pc = jumponcond(fs, e, 0);  /* jump when false */
  1148.       break;
  1149.     }
  1150.   }
  1151.   luaK_concat(fs, &e->f, pc);  /* insert new jump in false list */
  1152.   luaK_patchtohere(fs, e->t);  /* true list jumps to here (to go through) */
  1153.   e->t = NO_JUMP;
  1154. }
  1155.  
  1156.  
  1157. /*
  1158. ** Emit code to go through if 'e' is false, jump otherwise.
  1159. */
  1160. void luaK_goiffalse (FuncState *fs, expdesc *e) {
  1161.   int pc;  /* pc of new jump */
  1162.   luaK_dischargevars(fs, e);
  1163.   switch (e->k) {
  1164.     case VJMP: {
  1165.       pc = e->u.info;  /* already jump if true */
  1166.       break;
  1167.     }
  1168.     case VNIL: case VFALSE: {
  1169.       pc = NO_JUMP;  /* always false; do nothing */
  1170.       break;
  1171.     }
  1172.     default: {
  1173.       pc = jumponcond(fs, e, 1);  /* jump if true */
  1174.       break;
  1175.     }
  1176.   }
  1177.   luaK_concat(fs, &e->t, pc);  /* insert new jump in 't' list */
  1178.   luaK_patchtohere(fs, e->f);  /* false list jumps to here (to go through) */
  1179.   e->f = NO_JUMP;
  1180. }
  1181.  
  1182.  
  1183. /*
  1184. ** Code 'not e', doing constant folding.
  1185. */
  1186. static void codenot (FuncState *fs, expdesc *e) {
  1187.   switch (e->k) {
  1188.     case VNIL: case VFALSE: {
  1189.       e->k = VTRUE;  /* true == not nil == not false */
  1190.       break;
  1191.     }
  1192.     case VK: case VKFLT: case VKINT: case VKSTR: case VTRUE: {
  1193.       e->k = VFALSE;  /* false == not "x" == not 0.5 == not 1 == not true */
  1194.       break;
  1195.     }
  1196.     case VJMP: {
  1197.       negatecondition(fs, e);
  1198.       break;
  1199.     }
  1200.     case VRELOC:
  1201.     case VNONRELOC: {
  1202.       discharge2anyreg(fs, e);
  1203.       freeexp(fs, e);
  1204.       e->u.info = luaK_codeABC(fs, OP_NOT, 0, e->u.info, 0);
  1205.       e->k = VRELOC;
  1206.       break;
  1207.     }
  1208.     default: lua_assert(0);  /* cannot happen */
  1209.   }
  1210.   /* interchange true and false lists */
  1211.   { int temp = e->f; e->f = e->t; e->t = temp; }
  1212.   removevalues(fs, e->f);  /* values are useless when negated */
  1213.   removevalues(fs, e->t);
  1214. }
  1215.  
  1216.  
  1217. /*
  1218. ** Check whether expression 'e' is a small literal string
  1219. */
  1220. static int isKstr (FuncState *fs, expdesc *e) {
  1221.   return (e->k == VK && !hasjumps(e) && e->u.info <= MAXARG_B &&
  1222.           ttisshrstring(&fs->f->k[e->u.info]));
  1223. }
  1224.  
  1225. /*
  1226. ** Check whether expression 'e' is a literal integer.
  1227. */
  1228. int luaK_isKint (expdesc *e) {
  1229.   return (e->k == VKINT && !hasjumps(e));
  1230. }
  1231.  
  1232.  
  1233. /*
  1234. ** Check whether expression 'e' is a literal integer in
  1235. ** proper range to fit in register C
  1236. */
  1237. static int isCint (expdesc *e) {
  1238.   return luaK_isKint(e) && (l_castS2U(e->u.ival) <= l_castS2U(MAXARG_C));
  1239. }
  1240.  
  1241.  
  1242. /*
  1243. ** Check whether expression 'e' is a literal integer in
  1244. ** proper range to fit in register sC
  1245. */
  1246. static int isSCint (expdesc *e) {
  1247.   return luaK_isKint(e) && fitsC(e->u.ival);
  1248. }
  1249.  
  1250.  
  1251. /*
  1252. ** Check whether expression 'e' is a literal integer or float in
  1253. ** proper range to fit in a register (sB or sC).
  1254. */
  1255. static int isSCnumber (expdesc *e, int *pi, int *isfloat) {
  1256.   lua_Integer i;
  1257.   if (e->k == VKINT)
  1258.     i = e->u.ival;
  1259.   else if (e->k == VKFLT && luaV_flttointeger(e->u.nval, &i, F2Ieq))
  1260.     *isfloat = 1;
  1261.   else
  1262.     return 0;  /* not a number */
  1263.   if (!hasjumps(e) && fitsC(i)) {
  1264.     *pi = int2sC(cast_int(i));
  1265.     return 1;
  1266.   }
  1267.   else
  1268.     return 0;
  1269. }
  1270.  
  1271.  
  1272. /*
  1273. ** Create expression 't[k]'. 't' must have its final result already in a
  1274. ** register or upvalue. Upvalues can only be indexed by literal strings.
  1275. ** Keys can be literal strings in the constant table or arbitrary
  1276. ** values in registers.
  1277. */
  1278. void luaK_indexed (FuncState *fs, expdesc *t, expdesc *k) {
  1279.   if (k->k == VKSTR)
  1280.     str2K(fs, k);
  1281.   lua_assert(!hasjumps(t) &&
  1282.              (t->k == VLOCAL || t->k == VNONRELOC || t->k == VUPVAL));
  1283.   if (t->k == VUPVAL && !isKstr(fs, k))  /* upvalue indexed by non 'Kstr'? */
  1284.     luaK_exp2anyreg(fs, t);  /* put it in a register */
  1285.   if (t->k == VUPVAL) {
  1286.     t->u.ind.t = t->u.info;  /* upvalue index */
  1287.     t->u.ind.idx = k->u.info;  /* literal string */
  1288.     t->k = VINDEXUP;
  1289.   }
  1290.   else {
  1291.     /* register index of the table */
  1292.     t->u.ind.t = (t->k == VLOCAL) ? t->u.var.ridx: t->u.info;
  1293.     if (isKstr(fs, k)) {
  1294.       t->u.ind.idx = k->u.info;  /* literal string */
  1295.       t->k = VINDEXSTR;
  1296.     }
  1297.     else if (isCint(k)) {
  1298.       t->u.ind.idx = cast_int(k->u.ival);  /* int. constant in proper range */
  1299.       t->k = VINDEXI;
  1300.     }
  1301.     else {
  1302.       t->u.ind.idx = luaK_exp2anyreg(fs, k);  /* register */
  1303.       t->k = VINDEXED;
  1304.     }
  1305.   }
  1306. }
  1307.  
  1308.  
  1309. /*
  1310. ** Return false if folding can raise an error.
  1311. ** Bitwise operations need operands convertible to integers; division
  1312. ** operations cannot have 0 as divisor.
  1313. */
  1314. static int validop (int op, TValue *v1, TValue *v2) {
  1315.   switch (op) {
  1316.     case LUA_OPBAND: case LUA_OPBOR: case LUA_OPBXOR:
  1317.     case LUA_OPSHL: case LUA_OPSHR: case LUA_OPBNOT: {  /* conversion errors */
  1318.       lua_Integer i;
  1319.       return (luaV_tointegerns(v1, &i, LUA_FLOORN2I) &&
  1320.               luaV_tointegerns(v2, &i, LUA_FLOORN2I));
  1321.     }
  1322.     case LUA_OPDIV: case LUA_OPIDIV: case LUA_OPMOD:  /* division by 0 */
  1323.       return (nvalue(v2) != 0);
  1324.     default: return 1;  /* everything else is valid */
  1325.   }
  1326. }
  1327.  
  1328.  
  1329. /*
  1330. ** Try to "constant-fold" an operation; return 1 iff successful.
  1331. ** (In this case, 'e1' has the final result.)
  1332. */
  1333. static int constfolding (FuncState *fs, int op, expdesc *e1,
  1334.                                         const expdesc *e2) {
  1335.   TValue v1, v2, res;
  1336.   if (!tonumeral(e1, &v1) || !tonumeral(e2, &v2) || !validop(op, &v1, &v2))
  1337.     return 0;  /* non-numeric operands or not safe to fold */
  1338.   luaO_rawarith(fs->ls->L, op, &v1, &v2, &res);  /* does operation */
  1339.   if (ttisinteger(&res)) {
  1340.     e1->k = VKINT;
  1341.     e1->u.ival = ivalue(&res);
  1342.   }
  1343.   else {  /* folds neither NaN nor 0.0 (to avoid problems with -0.0) */
  1344.     lua_Number n = fltvalue(&res);
  1345.     if (luai_numisnan(n) || n == 0)
  1346.       return 0;
  1347.     e1->k = VKFLT;
  1348.     e1->u.nval = n;
  1349.   }
  1350.   return 1;
  1351. }
  1352.  
  1353.  
  1354. /*
  1355. ** Emit code for unary expressions that "produce values"
  1356. ** (everything but 'not').
  1357. ** Expression to produce final result will be encoded in 'e'.
  1358. */
  1359. static void codeunexpval (FuncState *fs, OpCode op, expdesc *e, int line) {
  1360.   int r = luaK_exp2anyreg(fs, e);  /* opcodes operate only on registers */
  1361.   freeexp(fs, e);
  1362.   e->u.info = luaK_codeABC(fs, op, 0, r, 0);  /* generate opcode */
  1363.   e->k = VRELOC;  /* all those operations are relocatable */
  1364.   luaK_fixline(fs, line);
  1365. }
  1366.  
  1367.  
  1368. /*
  1369. ** Emit code for binary expressions that "produce values"
  1370. ** (everything but logical operators 'and'/'or' and comparison
  1371. ** operators).
  1372. ** Expression to produce final result will be encoded in 'e1'.
  1373. */
  1374. static void finishbinexpval (FuncState *fs, expdesc *e1, expdesc *e2,
  1375.                              OpCode op, int v2, int flip, int line,
  1376.                              OpCode mmop, TMS event) {
  1377.   int v1 = luaK_exp2anyreg(fs, e1);
  1378.   int pc = luaK_codeABCk(fs, op, 0, v1, v2, 0);
  1379.   freeexps(fs, e1, e2);
  1380.   e1->u.info = pc;
  1381.   e1->k = VRELOC;  /* all those operations are relocatable */
  1382.   luaK_fixline(fs, line);
  1383.   luaK_codeABCk(fs, mmop, v1, v2, event, flip);  /* to call metamethod */
  1384.   luaK_fixline(fs, line);
  1385. }
  1386.  
  1387.  
  1388. /*
  1389. ** Emit code for binary expressions that "produce values" over
  1390. ** two registers.
  1391. */
  1392. static void codebinexpval (FuncState *fs, OpCode op,
  1393.                            expdesc *e1, expdesc *e2, int line) {
  1394.   int v2 = luaK_exp2anyreg(fs, e2);  /* both operands are in registers */
  1395.   lua_assert(OP_ADD <= op && op <= OP_SHR);
  1396.   finishbinexpval(fs, e1, e2, op, v2, 0, line, OP_MMBIN,
  1397.                   cast(TMS, (op - OP_ADD) + TM_ADD));
  1398. }
  1399.  
  1400.  
  1401. /*
  1402. ** Code binary operators with immediate operands.
  1403. */
  1404. static void codebini (FuncState *fs, OpCode op,
  1405.                        expdesc *e1, expdesc *e2, int flip, int line,
  1406.                        TMS event) {
  1407.   int v2 = int2sC(cast_int(e2->u.ival));  /* immediate operand */
  1408.   lua_assert(e2->k == VKINT);
  1409.   finishbinexpval(fs, e1, e2, op, v2, flip, line, OP_MMBINI, event);
  1410. }
  1411.  
  1412.  
  1413. /* Try to code a binary operator negating its second operand.
  1414. ** For the metamethod, 2nd operand must keep its original value.
  1415. */
  1416. static int finishbinexpneg (FuncState *fs, expdesc *e1, expdesc *e2,
  1417.                              OpCode op, int line, TMS event) {
  1418.   if (!luaK_isKint(e2))
  1419.     return 0;  /* not an integer constant */
  1420.   else {
  1421.     lua_Integer i2 = e2->u.ival;
  1422.     if (!(fitsC(i2) && fitsC(-i2)))
  1423.       return 0;  /* not in the proper range */
  1424.     else {  /* operating a small integer constant */
  1425.       int v2 = cast_int(i2);
  1426.       finishbinexpval(fs, e1, e2, op, int2sC(-v2), 0, line, OP_MMBINI, event);
  1427.       /* correct metamethod argument */
  1428.       SETARG_B(fs->f->code[fs->pc - 1], int2sC(v2));
  1429.       return 1;  /* successfully coded */
  1430.     }
  1431.   }
  1432. }
  1433.  
  1434.  
  1435. static void swapexps (expdesc *e1, expdesc *e2) {
  1436.   expdesc temp = *e1; *e1 = *e2; *e2 = temp;  /* swap 'e1' and 'e2' */
  1437. }
  1438.  
  1439.  
  1440. /*
  1441. ** Code arithmetic operators ('+', '-', ...). If second operand is a
  1442. ** constant in the proper range, use variant opcodes with K operands.
  1443. */
  1444. static void codearith (FuncState *fs, BinOpr opr,
  1445.                        expdesc *e1, expdesc *e2, int flip, int line) {
  1446.   TMS event = cast(TMS, opr + TM_ADD);
  1447.   if (tonumeral(e2, NULL) && luaK_exp2K(fs, e2)) {  /* K operand? */
  1448.     int v2 = e2->u.info;  /* K index */
  1449.     OpCode op = cast(OpCode, opr + OP_ADDK);
  1450.     finishbinexpval(fs, e1, e2, op, v2, flip, line, OP_MMBINK, event);
  1451.   }
  1452.   else {  /* 'e2' is neither an immediate nor a K operand */
  1453.     OpCode op = cast(OpCode, opr + OP_ADD);
  1454.     if (flip)
  1455.       swapexps(e1, e2);  /* back to original order */
  1456.     codebinexpval(fs, op, e1, e2, line);  /* use standard operators */
  1457.   }
  1458. }
  1459.  
  1460.  
  1461. /*
  1462. ** Code commutative operators ('+', '*'). If first operand is a
  1463. ** numeric constant, change order of operands to try to use an
  1464. ** immediate or K operator.
  1465. */
  1466. static void codecommutative (FuncState *fs, BinOpr op,
  1467.                              expdesc *e1, expdesc *e2, int line) {
  1468.   int flip = 0;
  1469.   if (tonumeral(e1, NULL)) {  /* is first operand a numeric constant? */
  1470.     swapexps(e1, e2);  /* change order */
  1471.     flip = 1;
  1472.   }
  1473.   if (op == OPR_ADD && isSCint(e2))  /* immediate operand? */
  1474.     codebini(fs, cast(OpCode, OP_ADDI), e1, e2, flip, line, TM_ADD);
  1475.   else
  1476.     codearith(fs, op, e1, e2, flip, line);
  1477. }
  1478.  
  1479.  
  1480. /*
  1481. ** Code bitwise operations; they are all associative, so the function
  1482. ** tries to put an integer constant as the 2nd operand (a K operand).
  1483. */
  1484. static void codebitwise (FuncState *fs, BinOpr opr,
  1485.                          expdesc *e1, expdesc *e2, int line) {
  1486.   int flip = 0;
  1487.   int v2;
  1488.   OpCode op;
  1489.   if (e1->k == VKINT && luaK_exp2RK(fs, e1)) {
  1490.     swapexps(e1, e2);  /* 'e2' will be the constant operand */
  1491.     flip = 1;
  1492.   }
  1493.   else if (!(e2->k == VKINT && luaK_exp2RK(fs, e2))) {  /* no constants? */
  1494.     op = cast(OpCode, opr + OP_ADD);
  1495.     codebinexpval(fs, op, e1, e2, line);  /* all-register opcodes */
  1496.     return;
  1497.   }
  1498.   v2 = e2->u.info;  /* index in K array */
  1499.   op = cast(OpCode, opr + OP_ADDK);
  1500.   lua_assert(ttisinteger(&fs->f->k[v2]));
  1501.   finishbinexpval(fs, e1, e2, op, v2, flip, line, OP_MMBINK,
  1502.                   cast(TMS, opr + TM_ADD));
  1503. }
  1504.  
  1505.  
  1506. /*
  1507. ** Emit code for order comparisons. When using an immediate operand,
  1508. ** 'isfloat' tells whether the original value was a float.
  1509. */
  1510. static void codeorder (FuncState *fs, OpCode op, expdesc *e1, expdesc *e2) {
  1511.   int r1, r2;
  1512.   int im;
  1513.   int isfloat = 0;
  1514.   if (isSCnumber(e2, &im, &isfloat)) {
  1515.     /* use immediate operand */
  1516.     r1 = luaK_exp2anyreg(fs, e1);
  1517.     r2 = im;
  1518.     op = cast(OpCode, (op - OP_LT) + OP_LTI);
  1519.   }
  1520.   else if (isSCnumber(e1, &im, &isfloat)) {
  1521.     /* transform (A < B) to (B > A) and (A <= B) to (B >= A) */
  1522.     r1 = luaK_exp2anyreg(fs, e2);
  1523.     r2 = im;
  1524.     op = (op == OP_LT) ? OP_GTI : OP_GEI;
  1525.   }
  1526.   else {  /* regular case, compare two registers */
  1527.     r1 = luaK_exp2anyreg(fs, e1);
  1528.     r2 = luaK_exp2anyreg(fs, e2);
  1529.   }
  1530.   freeexps(fs, e1, e2);
  1531.   e1->u.info = condjump(fs, op, r1, r2, isfloat, 1);
  1532.   e1->k = VJMP;
  1533. }
  1534.  
  1535.  
  1536. /*
  1537. ** Emit code for equality comparisons ('==', '~=').
  1538. ** 'e1' was already put as RK by 'luaK_infix'.
  1539. */
  1540. static void codeeq (FuncState *fs, BinOpr opr, expdesc *e1, expdesc *e2) {
  1541.   int r1, r2;
  1542.   int im;
  1543.   int isfloat = 0;  /* not needed here, but kept for symmetry */
  1544.   OpCode op;
  1545.   if (e1->k != VNONRELOC) {
  1546.     lua_assert(e1->k == VK || e1->k == VKINT || e1->k == VKFLT);
  1547.     swapexps(e1, e2);
  1548.   }
  1549.   r1 = luaK_exp2anyreg(fs, e1);  /* 1st expression must be in register */
  1550.   if (isSCnumber(e2, &im, &isfloat)) {
  1551.     op = OP_EQI;
  1552.     r2 = im;  /* immediate operand */
  1553.   }
  1554.   else if (luaK_exp2RK(fs, e2)) {  /* 1st expression is constant? */
  1555.     op = OP_EQK;
  1556.     r2 = e2->u.info;  /* constant index */
  1557.   }
  1558.   else {
  1559.     op = OP_EQ;  /* will compare two registers */
  1560.     r2 = luaK_exp2anyreg(fs, e2);
  1561.   }
  1562.   freeexps(fs, e1, e2);
  1563.   e1->u.info = condjump(fs, op, r1, r2, isfloat, (opr == OPR_EQ));
  1564.   e1->k = VJMP;
  1565. }
  1566.  
  1567.  
  1568. /*
  1569. ** Apply prefix operation 'op' to expression 'e'.
  1570. */
  1571. void luaK_prefix (FuncState *fs, UnOpr op, expdesc *e, int line) {
  1572.   static const expdesc ef = {VKINT, {0}, NO_JUMP, NO_JUMP};
  1573.   luaK_dischargevars(fs, e);
  1574.   switch (op) {
  1575.     case OPR_MINUS: case OPR_BNOT:  /* use 'ef' as fake 2nd operand */
  1576.       if (constfolding(fs, op + LUA_OPUNM, e, &ef))
  1577.         break;
  1578.       /* else */ /* FALLTHROUGH */
  1579.     case OPR_LEN:
  1580.       codeunexpval(fs, cast(OpCode, op + OP_UNM), e, line);
  1581.       break;
  1582.     case OPR_NOT: codenot(fs, e); break;
  1583.     default: lua_assert(0);
  1584.   }
  1585. }
  1586.  
  1587.  
  1588. /*
  1589. ** Process 1st operand 'v' of binary operation 'op' before reading
  1590. ** 2nd operand.
  1591. */
  1592. void luaK_infix (FuncState *fs, BinOpr op, expdesc *v) {
  1593.   luaK_dischargevars(fs, v);
  1594.   switch (op) {
  1595.     case OPR_AND: {
  1596.       luaK_goiftrue(fs, v);  /* go ahead only if 'v' is true */
  1597.       break;
  1598.     }
  1599.     case OPR_OR: {
  1600.       luaK_goiffalse(fs, v);  /* go ahead only if 'v' is false */
  1601.       break;
  1602.     }
  1603.     case OPR_CONCAT: {
  1604.       luaK_exp2nextreg(fs, v);  /* operand must be on the stack */
  1605.       break;
  1606.     }
  1607.     case OPR_ADD: case OPR_SUB:
  1608.     case OPR_MUL: case OPR_DIV: case OPR_IDIV:
  1609.     case OPR_MOD: case OPR_POW:
  1610.     case OPR_BAND: case OPR_BOR: case OPR_BXOR:
  1611.     case OPR_SHL: case OPR_SHR: {
  1612.       if (!tonumeral(v, NULL))
  1613.         luaK_exp2anyreg(fs, v);
  1614.       /* else keep numeral, which may be folded with 2nd operand */
  1615.       break;
  1616.     }
  1617.     case OPR_EQ: case OPR_NE: {
  1618.       if (!tonumeral(v, NULL))
  1619.         luaK_exp2RK(fs, v);
  1620.       /* else keep numeral, which may be an immediate operand */
  1621.       break;
  1622.     }
  1623.     case OPR_LT: case OPR_LE:
  1624.     case OPR_GT: case OPR_GE: {
  1625.       int dummy, dummy2;
  1626.       if (!isSCnumber(v, &dummy, &dummy2))
  1627.         luaK_exp2anyreg(fs, v);
  1628.       /* else keep numeral, which may be an immediate operand */
  1629.       break;
  1630.     }
  1631.     default: lua_assert(0);
  1632.   }
  1633. }
  1634.  
  1635. /*
  1636. ** Create code for '(e1 .. e2)'.
  1637. ** For '(e1 .. e2.1 .. e2.2)' (which is '(e1 .. (e2.1 .. e2.2))',
  1638. ** because concatenation is right associative), merge both CONCATs.
  1639. */
  1640. static void codeconcat (FuncState *fs, expdesc *e1, expdesc *e2, int line) {
  1641.   Instruction *ie2 = previousinstruction(fs);
  1642.   if (GET_OPCODE(*ie2) == OP_CONCAT) {  /* is 'e2' a concatenation? */
  1643.     int n = GETARG_B(*ie2);  /* # of elements concatenated in 'e2' */
  1644.     lua_assert(e1->u.info + 1 == GETARG_A(*ie2));
  1645.     freeexp(fs, e2);
  1646.     SETARG_A(*ie2, e1->u.info);  /* correct first element ('e1') */
  1647.     SETARG_B(*ie2, n + 1);  /* will concatenate one more element */
  1648.   }
  1649.   else {  /* 'e2' is not a concatenation */
  1650.     luaK_codeABC(fs, OP_CONCAT, e1->u.info, 2, 0);  /* new concat opcode */
  1651.     freeexp(fs, e2);
  1652.     luaK_fixline(fs, line);
  1653.   }
  1654. }
  1655.  
  1656.  
  1657. /*
  1658. ** Finalize code for binary operation, after reading 2nd operand.
  1659. */
  1660. void luaK_posfix (FuncState *fs, BinOpr opr,
  1661.                   expdesc *e1, expdesc *e2, int line) {
  1662.   luaK_dischargevars(fs, e2);
  1663.   if (foldbinop(opr) && constfolding(fs, opr + LUA_OPADD, e1, e2))
  1664.     return;  /* done by folding */
  1665.   switch (opr) {
  1666.     case OPR_AND: {
  1667.       lua_assert(e1->t == NO_JUMP);  /* list closed by 'luaK_infix' */
  1668.       luaK_concat(fs, &e2->f, e1->f);
  1669.       *e1 = *e2;
  1670.       break;
  1671.     }
  1672.     case OPR_OR: {
  1673.       lua_assert(e1->f == NO_JUMP);  /* list closed by 'luaK_infix' */
  1674.       luaK_concat(fs, &e2->t, e1->t);
  1675.       *e1 = *e2;
  1676.       break;
  1677.     }
  1678.     case OPR_CONCAT: {  /* e1 .. e2 */
  1679.       luaK_exp2nextreg(fs, e2);
  1680.       codeconcat(fs, e1, e2, line);
  1681.       break;
  1682.     }
  1683.     case OPR_ADD: case OPR_MUL: {
  1684.       codecommutative(fs, opr, e1, e2, line);
  1685.       break;
  1686.     }
  1687.     case OPR_SUB: {
  1688.       if (finishbinexpneg(fs, e1, e2, OP_ADDI, line, TM_SUB))
  1689.         break; /* coded as (r1 + -I) */
  1690.       /* ELSE */
  1691.     }  /* FALLTHROUGH */
  1692.     case OPR_DIV: case OPR_IDIV: case OPR_MOD: case OPR_POW: {
  1693.       codearith(fs, opr, e1, e2, 0, line);
  1694.       break;
  1695.     }
  1696.     case OPR_BAND: case OPR_BOR: case OPR_BXOR: {
  1697.       codebitwise(fs, opr, e1, e2, line);
  1698.       break;
  1699.     }
  1700.     case OPR_SHL: {
  1701.       if (isSCint(e1)) {
  1702.         swapexps(e1, e2);
  1703.         codebini(fs, OP_SHLI, e1, e2, 1, line, TM_SHL);  /* I << r2 */
  1704.       }
  1705.       else if (finishbinexpneg(fs, e1, e2, OP_SHRI, line, TM_SHL)) {
  1706.         /* coded as (r1 >> -I) */;
  1707.       }
  1708.       else  /* regular case (two registers) */
  1709.        codebinexpval(fs, OP_SHL, e1, e2, line);
  1710.       break;
  1711.     }
  1712.     case OPR_SHR: {
  1713.       if (isSCint(e2))
  1714.         codebini(fs, OP_SHRI, e1, e2, 0, line, TM_SHR);  /* r1 >> I */
  1715.       else  /* regular case (two registers) */
  1716.         codebinexpval(fs, OP_SHR, e1, e2, line);
  1717.       break;
  1718.     }
  1719.     case OPR_EQ: case OPR_NE: {
  1720.       codeeq(fs, opr, e1, e2);
  1721.       break;
  1722.     }
  1723.     case OPR_LT: case OPR_LE: {
  1724.       OpCode op = cast(OpCode, (opr - OPR_EQ) + OP_EQ);
  1725.       codeorder(fs, op, e1, e2);
  1726.       break;
  1727.     }
  1728.     case OPR_GT: case OPR_GE: {
  1729.       /* '(a > b)' <=> '(b < a)';  '(a >= b)' <=> '(b <= a)' */
  1730.       OpCode op = cast(OpCode, (opr - OPR_NE) + OP_EQ);
  1731.       swapexps(e1, e2);
  1732.       codeorder(fs, op, e1, e2);
  1733.       break;
  1734.     }
  1735.     default: lua_assert(0);
  1736.   }
  1737. }
  1738.  
  1739.  
  1740. /*
  1741. ** Change line information associated with current position, by removing
  1742. ** previous info and adding it again with new line.
  1743. */
  1744. void luaK_fixline (FuncState *fs, int line) {
  1745.   removelastlineinfo(fs);
  1746.   savelineinfo(fs, fs->f, line);
  1747. }
  1748.  
  1749.  
  1750. void luaK_settablesize (FuncState *fs, int pc, int ra, int asize, int hsize) {
  1751.   Instruction *inst = &fs->f->code[pc];
  1752.   int rb = (hsize != 0) ? luaO_ceillog2(hsize) + 1 : 0;  /* hash size */
  1753.   int extra = asize / (MAXARG_C + 1);  /* higher bits of array size */
  1754.   int rc = asize % (MAXARG_C + 1);  /* lower bits of array size */
  1755.   int k = (extra > 0);  /* true iff needs extra argument */
  1756.   *inst = CREATE_ABCk(OP_NEWTABLE, ra, rb, rc, k);
  1757.   *(inst + 1) = CREATE_Ax(OP_EXTRAARG, extra);
  1758. }
  1759.  
  1760.  
  1761. /*
  1762. ** Emit a SETLIST instruction.
  1763. ** 'base' is register that keeps table;
  1764. ** 'nelems' is #table plus those to be stored now;
  1765. ** 'tostore' is number of values (in registers 'base + 1',...) to add to
  1766. ** table (or LUA_MULTRET to add up to stack top).
  1767. */
  1768. void luaK_setlist (FuncState *fs, int base, int nelems, int tostore) {
  1769.   lua_assert(tostore != 0 && tostore <= LFIELDS_PER_FLUSH);
  1770.   if (tostore == LUA_MULTRET)
  1771.     tostore = 0;
  1772.   if (nelems <= MAXARG_C)
  1773.     luaK_codeABC(fs, OP_SETLIST, base, tostore, nelems);
  1774.   else {
  1775.     int extra = nelems / (MAXARG_C + 1);
  1776.     nelems %= (MAXARG_C + 1);
  1777.     luaK_codeABCk(fs, OP_SETLIST, base, tostore, nelems, 1);
  1778.     codeextraarg(fs, extra);
  1779.   }
  1780.   fs->freereg = base + 1;  /* free registers with list values */
  1781. }
  1782.  
  1783.  
  1784. /*
  1785. ** return the final target of a jump (skipping jumps to jumps)
  1786. */
  1787. static int finaltarget (Instruction *code, int i) {
  1788.   int count;
  1789.   for (count = 0; count < 100; count++) {  /* avoid infinite loops */
  1790.     Instruction pc = code[i];
  1791.     if (GET_OPCODE(pc) != OP_JMP)
  1792.       break;
  1793.      else
  1794.        i += GETARG_sJ(pc) + 1;
  1795.   }
  1796.   return i;
  1797. }
  1798.  
  1799.  
  1800. /*
  1801. ** Do a final pass over the code of a function, doing small peephole
  1802. ** optimizations and adjustments.
  1803. */
  1804. void luaK_finish (FuncState *fs) {
  1805.   int i;
  1806.   Proto *p = fs->f;
  1807.   for (i = 0; i < fs->pc; i++) {
  1808.     Instruction *pc = &p->code[i];
  1809.     lua_assert(i == 0 || isOT(*(pc - 1)) == isIT(*pc));
  1810.     switch (GET_OPCODE(*pc)) {
  1811.       case OP_RETURN0: case OP_RETURN1: {
  1812.         if (!(fs->needclose || p->is_vararg))
  1813.           break;  /* no extra work */
  1814.         /* else use OP_RETURN to do the extra work */
  1815.         SET_OPCODE(*pc, OP_RETURN);
  1816.       }  /* FALLTHROUGH */
  1817.       case OP_RETURN: case OP_TAILCALL: {
  1818.         if (fs->needclose)
  1819.           SETARG_k(*pc, 1);  /* signal that it needs to close */
  1820.         if (p->is_vararg)
  1821.           SETARG_C(*pc, p->numparams + 1);  /* signal that it is vararg */
  1822.         break;
  1823.       }
  1824.       case OP_JMP: {
  1825.         int target = finaltarget(p->code, i);
  1826.         fixjump(fs, i, target);
  1827.         break;
  1828.       }
  1829.       default: break;
  1830.     }
  1831.   }
  1832. }
  1833.