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Member "memcached-1.6.15/vendor/lua/src/lcode.c" (1 Oct 2021, 51130 Bytes) of package /linux/www/memcached-1.6.15.tar.gz:


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