mudgangster

Tiny, scriptable MUD client
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lcode.cc (34308B)


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