lua

lcode.c (54425B)

---

 /*
 ** $Id: lcode.c $
 ** Code generator for Lua
 ** See Copyright Notice in lua.h
 */
 
 #define lcode_c
 #define LUA_CORE
 
 #include "lprefix.h"
 
 
 #include <float.h>
 #include <limits.h>
 #include <math.h>
 #include <stdlib.h>
 
 #include "lua.h"
 
 #include "lcode.h"
 #include "ldebug.h"
 #include "ldo.h"
 #include "lgc.h"
 #include "llex.h"
 #include "lmem.h"
 #include "lobject.h"
 #include "lopcodes.h"
 #include "lparser.h"
 #include "lstring.h"
 #include "ltable.h"
 #include "lvm.h"
 
 
 /* (note that expressions VJMP also have jumps.) */
 #define hasjumps(e)	((e)->t != (e)->f)
 
 
 static int codesJ (FuncState *fs, OpCode o, int sj, int k);
 
 
 
 /* semantic error */
 l_noret luaK_semerror (LexState *ls, const char *msg) {
   ls->t.token = 0;  /* remove "near <token>" from final message */
   luaX_syntaxerror(ls, msg);
 }
 
 
 /*
 ** If expression is a numeric constant, fills 'v' with its value
 ** and returns 1. Otherwise, returns 0.
 */
 static int tonumeral (const expdesc *e, TValue *v) {
   if (hasjumps(e))
     return 0;  /* not a numeral */
   switch (e->k) {
     case VKINT:
       if (v) setivalue(v, e->u.ival);
       return 1;
     case VKFLT:
       if (v) setfltvalue(v, e->u.nval);
       return 1;
     default: return 0;
   }
 }
 
 
 /*
 ** Get the constant value from a constant expression
 */
 static TValue *const2val (FuncState *fs, const expdesc *e) {
   lua_assert(e->k == VCONST);
   return &fs->ls->dyd->actvar.arr[e->u.info].k;
 }
 
 
 /*
 ** If expression is a constant, fills 'v' with its value
 ** and returns 1. Otherwise, returns 0.
 */
 int luaK_exp2const (FuncState *fs, const expdesc *e, TValue *v) {
   if (hasjumps(e))
     return 0;  /* not a constant */
   switch (e->k) {
     case VFALSE:
       setbfvalue(v);
       return 1;
     case VTRUE:
       setbtvalue(v);
       return 1;
     case VNIL:
       setnilvalue(v);
       return 1;
     case VKSTR: {
       setsvalue(fs->ls->L, v, e->u.strval);
       return 1;
     }
     case VCONST: {
       setobj(fs->ls->L, v, const2val(fs, e));
       return 1;
     }
     default: return tonumeral(e, v);
   }
 }
 
 
 /*
 ** Return the previous instruction of the current code. If there
 ** may be a jump target between the current instruction and the
 ** previous one, return an invalid instruction (to avoid wrong
 ** optimizations).
 */
 static Instruction *previousinstruction (FuncState *fs) {
   static const Instruction invalidinstruction = ~(Instruction)0;
   if (fs->pc > fs->lasttarget)
     return &fs->f->code[fs->pc - 1];  /* previous instruction */
   else
     return cast(Instruction*, &invalidinstruction);
 }
 
 
 /*
 ** Create a OP_LOADNIL instruction, but try to optimize: if the previous
 ** instruction is also OP_LOADNIL and ranges are compatible, adjust
 ** range of previous instruction instead of emitting a new one. (For
 ** instance, 'local a; local b' will generate a single opcode.)
 */
 void luaK_nil (FuncState *fs, int from, int n) {
   int l = from + n - 1;  /* last register to set nil */
   Instruction *previous = previousinstruction(fs);
   if (GET_OPCODE(*previous) == OP_LOADNIL) {  /* previous is LOADNIL? */
     int pfrom = GETARG_A(*previous);  /* get previous range */
     int pl = pfrom + GETARG_B(*previous);
     if ((pfrom <= from && from <= pl + 1) ||
         (from <= pfrom && pfrom <= l + 1)) {  /* can connect both? */
       if (pfrom < from) from = pfrom;  /* from = min(from, pfrom) */
       if (pl > l) l = pl;  /* l = max(l, pl) */
       SETARG_A(*previous, from);
       SETARG_B(*previous, l - from);
       return;
     }  /* else go through */
   }
   luaK_codeABC(fs, OP_LOADNIL, from, n - 1, 0);  /* else no optimization */
 }
 
 
 /*
 ** Gets the destination address of a jump instruction. Used to traverse
 ** a list of jumps.
 */
 static int getjump (FuncState *fs, int pc) {
   int offset = GETARG_sJ(fs->f->code[pc]);
   if (offset == NO_JUMP)  /* point to itself represents end of list */
     return NO_JUMP;  /* end of list */
   else
     return (pc+1)+offset;  /* turn offset into absolute position */
 }
 
 
 /*
 ** Fix jump instruction at position 'pc' to jump to 'dest'.
 ** (Jump addresses are relative in Lua)
 */
 static void fixjump (FuncState *fs, int pc, int dest) {
   Instruction *jmp = &fs->f->code[pc];
   int offset = dest - (pc + 1);
   lua_assert(dest != NO_JUMP);
   if (!(-OFFSET_sJ <= offset && offset <= MAXARG_sJ - OFFSET_sJ))
     luaX_syntaxerror(fs->ls, "control structure too long");
   lua_assert(GET_OPCODE(*jmp) == OP_JMP);
   SETARG_sJ(*jmp, offset);
 }
 
 
 /*
 ** Concatenate jump-list 'l2' into jump-list 'l1'
 */
 void luaK_concat (FuncState *fs, int *l1, int l2) {
   if (l2 == NO_JUMP) return;  /* nothing to concatenate? */
   else if (*l1 == NO_JUMP)  /* no original list? */
     *l1 = l2;  /* 'l1' points to 'l2' */
   else {
     int list = *l1;
     int next;
     while ((next = getjump(fs, list)) != NO_JUMP)  /* find last element */
       list = next;
     fixjump(fs, list, l2);  /* last element links to 'l2' */
   }
 }
 
 
 /*
 ** Create a jump instruction and return its position, so its destination
 ** can be fixed later (with 'fixjump').
 */
 int luaK_jump (FuncState *fs) {
   return codesJ(fs, OP_JMP, NO_JUMP, 0);
 }
 
 
 /*
 ** Code a 'return' instruction
 */
 void luaK_ret (FuncState *fs, int first, int nret) {
   OpCode op;
   switch (nret) {
     case 0: op = OP_RETURN0; break;
     case 1: op = OP_RETURN1; break;
     default: op = OP_RETURN; break;
   }
   luaY_checklimit(fs, nret + 1, MAXARG_B, "returns");
   luaK_codeABC(fs, op, first, nret + 1, 0);
 }
 
 
 /*
 ** Code a "conditional jump", that is, a test or comparison opcode
 ** followed by a jump. Return jump position.
 */
 static int condjump (FuncState *fs, OpCode op, int A, int B, int C, int k) {
   luaK_codeABCk(fs, op, A, B, C, k);
   return luaK_jump(fs);
 }
 
 
 /*
 ** returns current 'pc' and marks it as a jump target (to avoid wrong
 ** optimizations with consecutive instructions not in the same basic block).
 */
 int luaK_getlabel (FuncState *fs) {
   fs->lasttarget = fs->pc;
   return fs->pc;
 }
 
 
 /*
 ** Returns the position of the instruction "controlling" a given
 ** jump (that is, its condition), or the jump itself if it is
 ** unconditional.
 */
 static Instruction *getjumpcontrol (FuncState *fs, int pc) {
   Instruction *pi = &fs->f->code[pc];
   if (pc >= 1 && testTMode(GET_OPCODE(*(pi-1))))
     return pi-1;
   else
     return pi;
 }
 
 
 /*
 ** Patch destination register for a TESTSET instruction.
 ** If instruction in position 'node' is not a TESTSET, return 0 ("fails").
 ** Otherwise, if 'reg' is not 'NO_REG', set it as the destination
 ** register. Otherwise, change instruction to a simple 'TEST' (produces
 ** no register value)
 */
 static int patchtestreg (FuncState *fs, int node, int reg) {
   Instruction *i = getjumpcontrol(fs, node);
   if (GET_OPCODE(*i) != OP_TESTSET)
     return 0;  /* cannot patch other instructions */
   if (reg != NO_REG && reg != GETARG_B(*i))
     SETARG_A(*i, reg);
   else {
      /* no register to put value or register already has the value;
         change instruction to simple test */
     *i = CREATE_ABCk(OP_TEST, GETARG_B(*i), 0, 0, GETARG_k(*i));
   }
   return 1;
 }
 
 
 /*
 ** Traverse a list of tests ensuring no one produces a value
 */
 static void removevalues (FuncState *fs, int list) {
   for (; list != NO_JUMP; list = getjump(fs, list))
       patchtestreg(fs, list, NO_REG);
 }
 
 
 /*
 ** Traverse a list of tests, patching their destination address and
 ** registers: tests producing values jump to 'vtarget' (and put their
 ** values in 'reg'), other tests jump to 'dtarget'.
 */
 static void patchlistaux (FuncState *fs, int list, int vtarget, int reg,
                           int dtarget) {
   while (list != NO_JUMP) {
     int next = getjump(fs, list);
     if (patchtestreg(fs, list, reg))
       fixjump(fs, list, vtarget);
     else
       fixjump(fs, list, dtarget);  /* jump to default target */
     list = next;
   }
 }
 
 
 /*
 ** Path all jumps in 'list' to jump to 'target'.
 ** (The assert means that we cannot fix a jump to a forward address
 ** because we only know addresses once code is generated.)
 */
 void luaK_patchlist (FuncState *fs, int list, int target) {
   lua_assert(target <= fs->pc);
   patchlistaux(fs, list, target, NO_REG, target);
 }
 
 
 void luaK_patchtohere (FuncState *fs, int list) {
   int hr = luaK_getlabel(fs);  /* mark "here" as a jump target */
   luaK_patchlist(fs, list, hr);
 }
 
 
 /* limit for difference between lines in relative line info. */
 #define LIMLINEDIFF	0x80
 
 
 /*
 ** Save line info for a new instruction. If difference from last line
 ** does not fit in a byte, of after that many instructions, save a new
 ** absolute line info; (in that case, the special value 'ABSLINEINFO'
 ** in 'lineinfo' signals the existence of this absolute information.)
 ** Otherwise, store the difference from last line in 'lineinfo'.
 */
 static void savelineinfo (FuncState *fs, Proto *f, int line) {
   int linedif = line - fs->previousline;
   int pc = fs->pc - 1;  /* last instruction coded */
   if (abs(linedif) >= LIMLINEDIFF || fs->iwthabs++ >= MAXIWTHABS) {
     luaM_growvector(fs->ls->L, f->abslineinfo, fs->nabslineinfo,
                     f->sizeabslineinfo, AbsLineInfo, INT_MAX, "lines");
     f->abslineinfo[fs->nabslineinfo].pc = pc;
     f->abslineinfo[fs->nabslineinfo++].line = line;
     linedif = ABSLINEINFO;  /* signal that there is absolute information */
     fs->iwthabs = 1;  /* restart counter */
   }
   luaM_growvector(fs->ls->L, f->lineinfo, pc, f->sizelineinfo, ls_byte,
                   INT_MAX, "opcodes");
   f->lineinfo[pc] = cast(ls_byte, linedif);
   fs->previousline = line;  /* last line saved */
 }
 
 
 /*
 ** Remove line information from the last instruction.
 ** If line information for that instruction is absolute, set 'iwthabs'
 ** above its max to force the new (replacing) instruction to have
 ** absolute line info, too.
 */
 static void removelastlineinfo (FuncState *fs) {
   Proto *f = fs->f;
   int pc = fs->pc - 1;  /* last instruction coded */
   if (f->lineinfo[pc] != ABSLINEINFO) {  /* relative line info? */
     fs->previousline -= f->lineinfo[pc];  /* correct last line saved */
     fs->iwthabs--;  /* undo previous increment */
   }
   else {  /* absolute line information */
     lua_assert(f->abslineinfo[fs->nabslineinfo - 1].pc == pc);
     fs->nabslineinfo--;  /* remove it */
     fs->iwthabs = MAXIWTHABS + 1;  /* force next line info to be absolute */
   }
 }
 
 
 /*
 ** Remove the last instruction created, correcting line information
 ** accordingly.
 */
 static void removelastinstruction (FuncState *fs) {
   removelastlineinfo(fs);
   fs->pc--;
 }
 
 
 /*
 ** Emit instruction 'i', checking for array sizes and saving also its
 ** line information. Return 'i' position.
 */
 int luaK_code (FuncState *fs, Instruction i) {
   Proto *f = fs->f;
   /* put new instruction in code array */
   luaM_growvector(fs->ls->L, f->code, fs->pc, f->sizecode, Instruction,
                   INT_MAX, "opcodes");
   f->code[fs->pc++] = i;
   savelineinfo(fs, f, fs->ls->lastline);
   return fs->pc - 1;  /* index of new instruction */
 }
 
 
 /*
 ** Format and emit an 'iABC' instruction. (Assertions check consistency
 ** of parameters versus opcode.)
 */
 int luaK_codeABCk (FuncState *fs, OpCode o, int A, int B, int C, int k) {
   lua_assert(getOpMode(o) == iABC);
   lua_assert(A <= MAXARG_A && B <= MAXARG_B &&
              C <= MAXARG_C && (k & ~1) == 0);
   return luaK_code(fs, CREATE_ABCk(o, A, B, C, k));
 }
 
 
 int luaK_codevABCk (FuncState *fs, OpCode o, int A, int B, int C, int k) {
   lua_assert(getOpMode(o) == ivABC);
   lua_assert(A <= MAXARG_A && B <= MAXARG_vB &&
              C <= MAXARG_vC && (k & ~1) == 0);
   return luaK_code(fs, CREATE_vABCk(o, A, B, C, k));
 }
 
 
 /*
 ** Format and emit an 'iABx' instruction.
 */
 int luaK_codeABx (FuncState *fs, OpCode o, int A, int Bc) {
   lua_assert(getOpMode(o) == iABx);
   lua_assert(A <= MAXARG_A && Bc <= MAXARG_Bx);
   return luaK_code(fs, CREATE_ABx(o, A, Bc));
 }
 
 
 /*
 ** Format and emit an 'iAsBx' instruction.
 */
 static int codeAsBx (FuncState *fs, OpCode o, int A, int Bc) {
   int b = Bc + OFFSET_sBx;
   lua_assert(getOpMode(o) == iAsBx);
   lua_assert(A <= MAXARG_A && b <= MAXARG_Bx);
   return luaK_code(fs, CREATE_ABx(o, A, b));
 }
 
 
 /*
 ** Format and emit an 'isJ' instruction.
 */
 static int codesJ (FuncState *fs, OpCode o, int sj, int k) {
   int j = sj + OFFSET_sJ;
   lua_assert(getOpMode(o) == isJ);
   lua_assert(j <= MAXARG_sJ && (k & ~1) == 0);
   return luaK_code(fs, CREATE_sJ(o, j, k));
 }
 
 
 /*
 ** Emit an "extra argument" instruction (format 'iAx')
 */
 static int codeextraarg (FuncState *fs, int A) {
   lua_assert(A <= MAXARG_Ax);
   return luaK_code(fs, CREATE_Ax(OP_EXTRAARG, A));
 }
 
 
 /*
 ** Emit a "load constant" instruction, using either 'OP_LOADK'
 ** (if constant index 'k' fits in 18 bits) or an 'OP_LOADKX'
 ** instruction with "extra argument".
 */
 static int luaK_codek (FuncState *fs, int reg, int k) {
   if (k <= MAXARG_Bx)
     return luaK_codeABx(fs, OP_LOADK, reg, k);
   else {
     int p = luaK_codeABx(fs, OP_LOADKX, reg, 0);
     codeextraarg(fs, k);
     return p;
   }
 }
 
 
 /*
 ** Check register-stack level, keeping track of its maximum size
 ** in field 'maxstacksize'
 */
 void luaK_checkstack (FuncState *fs, int n) {
   int newstack = fs->freereg + n;
   if (newstack > fs->f->maxstacksize) {
     luaY_checklimit(fs, newstack, MAX_FSTACK, "registers");
     fs->f->maxstacksize = cast_byte(newstack);
   }
 }
 
 
 /*
 ** Reserve 'n' registers in register stack
 */
 void luaK_reserveregs (FuncState *fs, int n) {
   luaK_checkstack(fs, n);
   fs->freereg =  cast_byte(fs->freereg + n);
 }
 
 
 /*
 ** Free register 'reg', if it is neither a constant index nor
 ** a local variable.
 )
 */
 static void freereg (FuncState *fs, int reg) {
   if (reg >= luaY_nvarstack(fs)) {
     fs->freereg--;
     lua_assert(reg == fs->freereg);
   }
 }
 
 
 /*
 ** Free two registers in proper order
 */
 static void freeregs (FuncState *fs, int r1, int r2) {
   if (r1 > r2) {
     freereg(fs, r1);
     freereg(fs, r2);
   }
   else {
     freereg(fs, r2);
     freereg(fs, r1);
   }
 }
 
 
 /*
 ** Free register used by expression 'e' (if any)
 */
 static void freeexp (FuncState *fs, expdesc *e) {
   if (e->k == VNONRELOC)
     freereg(fs, e->u.info);
 }
 
 
 /*
 ** Free registers used by expressions 'e1' and 'e2' (if any) in proper
 ** order.
 */
 static void freeexps (FuncState *fs, expdesc *e1, expdesc *e2) {
   int r1 = (e1->k == VNONRELOC) ? e1->u.info : -1;
   int r2 = (e2->k == VNONRELOC) ? e2->u.info : -1;
   freeregs(fs, r1, r2);
 }
 
 
 /*
 ** Add constant 'v' to prototype's list of constants (field 'k').
 */
 static int addk (FuncState *fs, Proto *f, TValue *v) {
   lua_State *L = fs->ls->L;
   int oldsize = f->sizek;
   int k = fs->nk;
   luaM_growvector(L, f->k, k, f->sizek, TValue, MAXARG_Ax, "constants");
   while (oldsize < f->sizek)
     setnilvalue(&f->k[oldsize++]);
   setobj(L, &f->k[k], v);
   fs->nk++;
   luaC_barrier(L, f, v);
   return k;
 }
 
 
 /*
 ** Use scanner's table to cache position of constants in constant list
 ** and try to reuse constants. Because some values should not be used
 ** as keys (nil cannot be a key, integer keys can collapse with float
 ** keys), the caller must provide a useful 'key' for indexing the cache.
 */
 static int k2proto (FuncState *fs, TValue *key, TValue *v) {
   TValue val;
   Proto *f = fs->f;
   int tag = luaH_get(fs->kcache, key, &val);  /* query scanner table */
   int k;
   if (!tagisempty(tag)) {  /* is there an index there? */
     k = cast_int(ivalue(&val));
     /* collisions can happen only for float keys */
     lua_assert(ttisfloat(key) || luaV_rawequalobj(&f->k[k], v));
     return k;  /* reuse index */
   }
   /* constant not found; create a new entry */
   k = addk(fs, f, v);
   /* cache it for reuse; numerical value does not need GC barrier;
      table is not a metatable, so it does not need to invalidate cache */
   setivalue(&val, k);
   luaH_set(fs->ls->L, fs->kcache, key, &val);
   return k;
 }
 
 
 /*
 ** Add a string to list of constants and return its index.
 */
 static int stringK (FuncState *fs, TString *s) {
   TValue o;
   setsvalue(fs->ls->L, &o, s);
   return k2proto(fs, &o, &o);  /* use string itself as key */
 }
 
 
 /*
 ** Add an integer to list of constants and return its index.
 */
 static int luaK_intK (FuncState *fs, lua_Integer n) {
   TValue o;
   setivalue(&o, n);
   return k2proto(fs, &o, &o);  /* use integer itself as key */
 }
 
 /*
 ** Add a float to list of constants and return its index. Floats
 ** with integral values need a different key, to avoid collision
 ** with actual integers. To that, we add to the number its smaller
 ** power-of-two fraction that is still significant in its scale.
 ** For doubles, that would be 1/2^52.
 ** This method is not bulletproof: different numbers may generate the
 ** same key (e.g., very large numbers will overflow to 'inf') and for
 ** floats larger than 2^53 the result is still an integer. At worst,
 ** this only wastes an entry with a duplicate.
 */
 static int luaK_numberK (FuncState *fs, lua_Number r) {
   TValue o, kv;
   setfltvalue(&o, r);  /* value as a TValue */
   if (r == 0) {  /* handle zero as a special case */
     setpvalue(&kv, fs);  /* use FuncState as index */
     return k2proto(fs, &kv, &o);  /* cannot collide */
   }
   else {
     const int nbm = l_floatatt(MANT_DIG);
     const lua_Number q = l_mathop(ldexp)(l_mathop(1.0), -nbm + 1);
     const lua_Number k =  r * (1 + q);  /* key */
     lua_Integer ik;
     setfltvalue(&kv, k);  /* key as a TValue */
     if (!luaV_flttointeger(k, &ik, F2Ieq)) {  /* not an integral value? */
       int n = k2proto(fs, &kv, &o);  /* use key */
       if (luaV_rawequalobj(&fs->f->k[n], &o))  /* correct value? */
         return n;
     }
     /* else, either key is still an integer or there was a collision;
        anyway, do not try to reuse constant; instead, create a new one */
     return addk(fs, fs->f, &o);
   }
 }
 
 
 /*
 ** Add a false to list of constants and return its index.
 */
 static int boolF (FuncState *fs) {
   TValue o;
   setbfvalue(&o);
   return k2proto(fs, &o, &o);  /* use boolean itself as key */
 }
 
 
 /*
 ** Add a true to list of constants and return its index.
 */
 static int boolT (FuncState *fs) {
   TValue o;
   setbtvalue(&o);
   return k2proto(fs, &o, &o);  /* use boolean itself as key */
 }
 
 
 /*
 ** Add nil to list of constants and return its index.
 */
 static int nilK (FuncState *fs) {
   TValue k, v;
   setnilvalue(&v);
   /* cannot use nil as key; instead use table itself */
   sethvalue(fs->ls->L, &k, fs->kcache);
   return k2proto(fs, &k, &v);
 }
 
 
 /*
 ** Check whether 'i' can be stored in an 'sC' operand. Equivalent to
 ** (0 <= int2sC(i) && int2sC(i) <= MAXARG_C) but without risk of
 ** overflows in the hidden addition inside 'int2sC'.
 */
 static int fitsC (lua_Integer i) {
   return (l_castS2U(i) + OFFSET_sC <= cast_uint(MAXARG_C));
 }
 
 
 /*
 ** Check whether 'i' can be stored in an 'sBx' operand.
 */
 static int fitsBx (lua_Integer i) {
   return (-OFFSET_sBx <= i && i <= MAXARG_Bx - OFFSET_sBx);
 }
 
 
 void luaK_int (FuncState *fs, int reg, lua_Integer i) {
   if (fitsBx(i))
     codeAsBx(fs, OP_LOADI, reg, cast_int(i));
   else
     luaK_codek(fs, reg, luaK_intK(fs, i));
 }
 
 
 static void luaK_float (FuncState *fs, int reg, lua_Number f) {
   lua_Integer fi;
   if (luaV_flttointeger(f, &fi, F2Ieq) && fitsBx(fi))
     codeAsBx(fs, OP_LOADF, reg, cast_int(fi));
   else
     luaK_codek(fs, reg, luaK_numberK(fs, f));
 }
 
 
 /*
 ** Convert a constant in 'v' into an expression description 'e'
 */
 static void const2exp (TValue *v, expdesc *e) {
   switch (ttypetag(v)) {
     case LUA_VNUMINT:
       e->k = VKINT; e->u.ival = ivalue(v);
       break;
     case LUA_VNUMFLT:
       e->k = VKFLT; e->u.nval = fltvalue(v);
       break;
     case LUA_VFALSE:
       e->k = VFALSE;
       break;
     case LUA_VTRUE:
       e->k = VTRUE;
       break;
     case LUA_VNIL:
       e->k = VNIL;
       break;
     case LUA_VSHRSTR:  case LUA_VLNGSTR:
       e->k = VKSTR; e->u.strval = tsvalue(v);
       break;
     default: lua_assert(0);
   }
 }
 
 
 /*
 ** Fix an expression to return the number of results 'nresults'.
 ** 'e' must be a multi-ret expression (function call or vararg).
 */
 void luaK_setreturns (FuncState *fs, expdesc *e, int nresults) {
   Instruction *pc = &getinstruction(fs, e);
   luaY_checklimit(fs, nresults + 1, MAXARG_C, "multiple results");
   if (e->k == VCALL)  /* expression is an open function call? */
     SETARG_C(*pc, nresults + 1);
   else {
     lua_assert(e->k == VVARARG);
     SETARG_C(*pc, nresults + 1);
     SETARG_A(*pc, fs->freereg);
     luaK_reserveregs(fs, 1);
   }
 }
 
 
 /*
 ** Convert a VKSTR to a VK
 */
 static void str2K (FuncState *fs, expdesc *e) {
   lua_assert(e->k == VKSTR);
   e->u.info = stringK(fs, e->u.strval);
   e->k = VK;
 }
 
 
 /*
 ** Fix an expression to return one result.
 ** If expression is not a multi-ret expression (function call or
 ** vararg), it already returns one result, so nothing needs to be done.
 ** Function calls become VNONRELOC expressions (as its result comes
 ** fixed in the base register of the call), while vararg expressions
 ** become VRELOC (as OP_VARARG puts its results where it wants).
 ** (Calls are created returning one result, so that does not need
 ** to be fixed.)
 */
 void luaK_setoneret (FuncState *fs, expdesc *e) {
   if (e->k == VCALL) {  /* expression is an open function call? */
     /* already returns 1 value */
     lua_assert(GETARG_C(getinstruction(fs, e)) == 2);
     e->k = VNONRELOC;  /* result has fixed position */
     e->u.info = GETARG_A(getinstruction(fs, e));
   }
   else if (e->k == VVARARG) {
     SETARG_C(getinstruction(fs, e), 2);
     e->k = VRELOC;  /* can relocate its simple result */
   }
 }
 
 
 /*
 ** Ensure that expression 'e' is not a variable (nor a <const>).
 ** (Expression still may have jump lists.)
 */
 void luaK_dischargevars (FuncState *fs, expdesc *e) {
   switch (e->k) {
     case VCONST: {
       const2exp(const2val(fs, e), e);
       break;
     }
     case VLOCAL: {  /* already in a register */
       int temp = e->u.var.ridx;
       e->u.info = temp;  /* (can't do a direct assignment; values overlap) */
       e->k = VNONRELOC;  /* becomes a non-relocatable value */
       break;
     }
     case VUPVAL: {  /* move value to some (pending) register */
       e->u.info = luaK_codeABC(fs, OP_GETUPVAL, 0, e->u.info, 0);
       e->k = VRELOC;
       break;
     }
     case VINDEXUP: {
       e->u.info = luaK_codeABC(fs, OP_GETTABUP, 0, e->u.ind.t, e->u.ind.idx);
       e->k = VRELOC;
       break;
     }
     case VINDEXI: {
       freereg(fs, e->u.ind.t);
       e->u.info = luaK_codeABC(fs, OP_GETI, 0, e->u.ind.t, e->u.ind.idx);
       e->k = VRELOC;
       break;
     }
     case VINDEXSTR: {
       freereg(fs, e->u.ind.t);
       e->u.info = luaK_codeABC(fs, OP_GETFIELD, 0, e->u.ind.t, e->u.ind.idx);
       e->k = VRELOC;
       break;
     }
     case VINDEXED: {
       freeregs(fs, e->u.ind.t, e->u.ind.idx);
       e->u.info = luaK_codeABC(fs, OP_GETTABLE, 0, e->u.ind.t, e->u.ind.idx);
       e->k = VRELOC;
       break;
     }
     case VVARARG: case VCALL: {
       luaK_setoneret(fs, e);
       break;
     }
     default: break;  /* there is one value available (somewhere) */
   }
 }
 
 
 /*
 ** Ensure expression value is in register 'reg', making 'e' a
 ** non-relocatable expression.
 ** (Expression still may have jump lists.)
 */
 static void discharge2reg (FuncState *fs, expdesc *e, int reg) {
   luaK_dischargevars(fs, e);
   switch (e->k) {
     case VNIL: {
       luaK_nil(fs, reg, 1);
       break;
     }
     case VFALSE: {
       luaK_codeABC(fs, OP_LOADFALSE, reg, 0, 0);
       break;
     }
     case VTRUE: {
       luaK_codeABC(fs, OP_LOADTRUE, reg, 0, 0);
       break;
     }
     case VKSTR: {
       str2K(fs, e);
     }  /* FALLTHROUGH */
     case VK: {
       luaK_codek(fs, reg, e->u.info);
       break;
     }
     case VKFLT: {
       luaK_float(fs, reg, e->u.nval);
       break;
     }
     case VKINT: {
       luaK_int(fs, reg, e->u.ival);
       break;
     }
     case VRELOC: {
       Instruction *pc = &getinstruction(fs, e);
       SETARG_A(*pc, reg);  /* instruction will put result in 'reg' */
       break;
     }
     case VNONRELOC: {
       if (reg != e->u.info)
         luaK_codeABC(fs, OP_MOVE, reg, e->u.info, 0);
       break;
     }
     default: {
       lua_assert(e->k == VJMP);
       return;  /* nothing to do... */
     }
   }
   e->u.info = reg;
   e->k = VNONRELOC;
 }
 
 
 /*
 ** Ensure expression value is in a register, making 'e' a
 ** non-relocatable expression.
 ** (Expression still may have jump lists.)
 */
 static void discharge2anyreg (FuncState *fs, expdesc *e) {
   if (e->k != VNONRELOC) {  /* no fixed register yet? */
     luaK_reserveregs(fs, 1);  /* get a register */
     discharge2reg(fs, e, fs->freereg-1);  /* put value there */
   }
 }
 
 
 static int code_loadbool (FuncState *fs, int A, OpCode op) {
   luaK_getlabel(fs);  /* those instructions may be jump targets */
   return luaK_codeABC(fs, op, A, 0, 0);
 }
 
 
 /*
 ** check whether list has any jump that do not produce a value
 ** or produce an inverted value
 */
 static int need_value (FuncState *fs, int list) {
   for (; list != NO_JUMP; list = getjump(fs, list)) {
     Instruction i = *getjumpcontrol(fs, list);
     if (GET_OPCODE(i) != OP_TESTSET) return 1;
   }
   return 0;  /* not found */
 }
 
 
 /*
 ** Ensures final expression result (which includes results from its
 ** jump lists) is in register 'reg'.
 ** If expression has jumps, need to patch these jumps either to
 ** its final position or to "load" instructions (for those tests
 ** that do not produce values).
 */
 static void exp2reg (FuncState *fs, expdesc *e, int reg) {
   discharge2reg(fs, e, reg);
   if (e->k == VJMP)  /* expression itself is a test? */
     luaK_concat(fs, &e->t, e->u.info);  /* put this jump in 't' list */
   if (hasjumps(e)) {
     int final;  /* position after whole expression */
     int p_f = NO_JUMP;  /* position of an eventual LOAD false */
     int p_t = NO_JUMP;  /* position of an eventual LOAD true */
     if (need_value(fs, e->t) || need_value(fs, e->f)) {
       int fj = (e->k == VJMP) ? NO_JUMP : luaK_jump(fs);
       p_f = code_loadbool(fs, reg, OP_LFALSESKIP);  /* skip next inst. */
       p_t = code_loadbool(fs, reg, OP_LOADTRUE);
       /* jump around these booleans if 'e' is not a test */
       luaK_patchtohere(fs, fj);
     }
     final = luaK_getlabel(fs);
     patchlistaux(fs, e->f, final, reg, p_f);
     patchlistaux(fs, e->t, final, reg, p_t);
   }
   e->f = e->t = NO_JUMP;
   e->u.info = reg;
   e->k = VNONRELOC;
 }
 
 
 /*
 ** Ensures final expression result is in next available register.
 */
 void luaK_exp2nextreg (FuncState *fs, expdesc *e) {
   luaK_dischargevars(fs, e);
   freeexp(fs, e);
   luaK_reserveregs(fs, 1);
   exp2reg(fs, e, fs->freereg - 1);
 }
 
 
 /*
 ** Ensures final expression result is in some (any) register
 ** and return that register.
 */
 int luaK_exp2anyreg (FuncState *fs, expdesc *e) {
   luaK_dischargevars(fs, e);
   if (e->k == VNONRELOC) {  /* expression already has a register? */
     if (!hasjumps(e))  /* no jumps? */
       return e->u.info;  /* result is already in a register */
     if (e->u.info >= luaY_nvarstack(fs)) {  /* reg. is not a local? */
       exp2reg(fs, e, e->u.info);  /* put final result in it */
       return e->u.info;
     }
     /* else expression has jumps and cannot change its register
        to hold the jump values, because it is a local variable.
        Go through to the default case. */
   }
   luaK_exp2nextreg(fs, e);  /* default: use next available register */
   return e->u.info;
 }
 
 
 /*
 ** Ensures final expression result is either in a register
 ** or in an upvalue.
 */
 void luaK_exp2anyregup (FuncState *fs, expdesc *e) {
   if (e->k != VUPVAL || hasjumps(e))
     luaK_exp2anyreg(fs, e);
 }
 
 
 /*
 ** Ensures final expression result is either in a register
 ** or it is a constant.
 */
 void luaK_exp2val (FuncState *fs, expdesc *e) {
   if (e->k == VJMP || hasjumps(e))
     luaK_exp2anyreg(fs, e);
   else
     luaK_dischargevars(fs, e);
 }
 
 
 /*
 ** Try to make 'e' a K expression with an index in the range of R/K
 ** indices. Return true iff succeeded.
 */
 static int luaK_exp2K (FuncState *fs, expdesc *e) {
   if (!hasjumps(e)) {
     int info;
     switch (e->k) {  /* move constants to 'k' */
       case VTRUE: info = boolT(fs); break;
       case VFALSE: info = boolF(fs); break;
       case VNIL: info = nilK(fs); break;
       case VKINT: info = luaK_intK(fs, e->u.ival); break;
       case VKFLT: info = luaK_numberK(fs, e->u.nval); break;
       case VKSTR: info = stringK(fs, e->u.strval); break;
       case VK: info = e->u.info; break;
       default: return 0;  /* not a constant */
     }
     if (info <= MAXINDEXRK) {  /* does constant fit in 'argC'? */
       e->k = VK;  /* make expression a 'K' expression */
       e->u.info = info;
       return 1;
     }
   }
   /* else, expression doesn't fit; leave it unchanged */
   return 0;
 }
 
 
 /*
 ** Ensures final expression result is in a valid R/K index
 ** (that is, it is either in a register or in 'k' with an index
 ** in the range of R/K indices).
 ** Returns 1 iff expression is K.
 */
 static int exp2RK (FuncState *fs, expdesc *e) {
   if (luaK_exp2K(fs, e))
     return 1;
   else {  /* not a constant in the right range: put it in a register */
     luaK_exp2anyreg(fs, e);
     return 0;
   }
 }
 
 
 static void codeABRK (FuncState *fs, OpCode o, int A, int B,
                       expdesc *ec) {
   int k = exp2RK(fs, ec);
   luaK_codeABCk(fs, o, A, B, ec->u.info, k);
 }
 
 
 /*
 ** Generate code to store result of expression 'ex' into variable 'var'.
 */
 void luaK_storevar (FuncState *fs, expdesc *var, expdesc *ex) {
   switch (var->k) {
     case VLOCAL: {
       freeexp(fs, ex);
       exp2reg(fs, ex, var->u.var.ridx);  /* compute 'ex' into proper place */
       return;
     }
     case VUPVAL: {
       int e = luaK_exp2anyreg(fs, ex);
       luaK_codeABC(fs, OP_SETUPVAL, e, var->u.info, 0);
       break;
     }
     case VINDEXUP: {
       codeABRK(fs, OP_SETTABUP, var->u.ind.t, var->u.ind.idx, ex);
       break;
     }
     case VINDEXI: {
       codeABRK(fs, OP_SETI, var->u.ind.t, var->u.ind.idx, ex);
       break;
     }
     case VINDEXSTR: {
       codeABRK(fs, OP_SETFIELD, var->u.ind.t, var->u.ind.idx, ex);
       break;
     }
     case VINDEXED: {
       codeABRK(fs, OP_SETTABLE, var->u.ind.t, var->u.ind.idx, ex);
       break;
     }
     default: lua_assert(0);  /* invalid var kind to store */
   }
   freeexp(fs, ex);
 }
 
 
 /*
 ** Negate condition 'e' (where 'e' is a comparison).
 */
 static void negatecondition (FuncState *fs, expdesc *e) {
   Instruction *pc = getjumpcontrol(fs, e->u.info);
   lua_assert(testTMode(GET_OPCODE(*pc)) && GET_OPCODE(*pc) != OP_TESTSET &&
                                            GET_OPCODE(*pc) != OP_TEST);
   SETARG_k(*pc, (GETARG_k(*pc) ^ 1));
 }
 
 
 /*
 ** Emit instruction to jump if 'e' is 'cond' (that is, if 'cond'
 ** is true, code will jump if 'e' is true.) Return jump position.
 ** Optimize when 'e' is 'not' something, inverting the condition
 ** and removing the 'not'.
 */
 static int jumponcond (FuncState *fs, expdesc *e, int cond) {
   if (e->k == VRELOC) {
     Instruction ie = getinstruction(fs, e);
     if (GET_OPCODE(ie) == OP_NOT) {
       removelastinstruction(fs);  /* remove previous OP_NOT */
       return condjump(fs, OP_TEST, GETARG_B(ie), 0, 0, !cond);
     }
     /* else go through */
   }
   discharge2anyreg(fs, e);
   freeexp(fs, e);
   return condjump(fs, OP_TESTSET, NO_REG, e->u.info, 0, cond);
 }
 
 
 /*
 ** Emit code to go through if 'e' is true, jump otherwise.
 */
 void luaK_goiftrue (FuncState *fs, expdesc *e) {
   int pc;  /* pc of new jump */
   luaK_dischargevars(fs, e);
   switch (e->k) {
     case VJMP: {  /* condition? */
       negatecondition(fs, e);  /* jump when it is false */
       pc = e->u.info;  /* save jump position */
       break;
     }
     case VK: case VKFLT: case VKINT: case VKSTR: case VTRUE: {
       pc = NO_JUMP;  /* always true; do nothing */
       break;
     }
     default: {
       pc = jumponcond(fs, e, 0);  /* jump when false */
       break;
     }
   }
   luaK_concat(fs, &e->f, pc);  /* insert new jump in false list */
   luaK_patchtohere(fs, e->t);  /* true list jumps to here (to go through) */
   e->t = NO_JUMP;
 }
 
 
 /*
 ** Emit code to go through if 'e' is false, jump otherwise.
 */
 void luaK_goiffalse (FuncState *fs, expdesc *e) {
   int pc;  /* pc of new jump */
   luaK_dischargevars(fs, e);
   switch (e->k) {
     case VJMP: {
       pc = e->u.info;  /* already jump if true */
       break;
     }
     case VNIL: case VFALSE: {
       pc = NO_JUMP;  /* always false; do nothing */
       break;
     }
     default: {
       pc = jumponcond(fs, e, 1);  /* jump if true */
       break;
     }
   }
   luaK_concat(fs, &e->t, pc);  /* insert new jump in 't' list */
   luaK_patchtohere(fs, e->f);  /* false list jumps to here (to go through) */
   e->f = NO_JUMP;
 }
 
 
 /*
 ** Code 'not e', doing constant folding.
 */
 static void codenot (FuncState *fs, expdesc *e) {
   switch (e->k) {
     case VNIL: case VFALSE: {
       e->k = VTRUE;  /* true == not nil == not false */
       break;
     }
     case VK: case VKFLT: case VKINT: case VKSTR: case VTRUE: {
       e->k = VFALSE;  /* false == not "x" == not 0.5 == not 1 == not true */
       break;
     }
     case VJMP: {
       negatecondition(fs, e);
       break;
     }
     case VRELOC:
     case VNONRELOC: {
       discharge2anyreg(fs, e);
       freeexp(fs, e);
       e->u.info = luaK_codeABC(fs, OP_NOT, 0, e->u.info, 0);
       e->k = VRELOC;
       break;
     }
     default: lua_assert(0);  /* cannot happen */
   }
   /* interchange true and false lists */
   { int temp = e->f; e->f = e->t; e->t = temp; }
   removevalues(fs, e->f);  /* values are useless when negated */
   removevalues(fs, e->t);
 }
 
 
 /*
 ** Check whether expression 'e' is a short literal string
 */
 static int isKstr (FuncState *fs, expdesc *e) {
   return (e->k == VK && !hasjumps(e) && e->u.info <= MAXARG_B &&
           ttisshrstring(&fs->f->k[e->u.info]));
 }
 
 /*
 ** Check whether expression 'e' is a literal integer.
 */
 static int isKint (expdesc *e) {
   return (e->k == VKINT && !hasjumps(e));
 }
 
 
 /*
 ** Check whether expression 'e' is a literal integer in
 ** proper range to fit in register C
 */
 static int isCint (expdesc *e) {
   return isKint(e) && (l_castS2U(e->u.ival) <= l_castS2U(MAXARG_C));
 }
 
 
 /*
 ** Check whether expression 'e' is a literal integer in
 ** proper range to fit in register sC
 */
 static int isSCint (expdesc *e) {
   return isKint(e) && fitsC(e->u.ival);
 }
 
 
 /*
 ** Check whether expression 'e' is a literal integer or float in
 ** proper range to fit in a register (sB or sC).
 */
 static int isSCnumber (expdesc *e, int *pi, int *isfloat) {
   lua_Integer i;
   if (e->k == VKINT)
     i = e->u.ival;
   else if (e->k == VKFLT && luaV_flttointeger(e->u.nval, &i, F2Ieq))
     *isfloat = 1;
   else
     return 0;  /* not a number */
   if (!hasjumps(e) && fitsC(i)) {
     *pi = int2sC(cast_int(i));
     return 1;
   }
   else
     return 0;
 }
 
 
 /*
 ** Emit SELF instruction or equivalent: the code will convert
 ** expression 'e' into 'e.key(e,'.
 */
 void luaK_self (FuncState *fs, expdesc *e, expdesc *key) {
   int ereg, base;
   luaK_exp2anyreg(fs, e);
   ereg = e->u.info;  /* register where 'e' (the receiver) was placed */
   freeexp(fs, e);
   base = e->u.info = fs->freereg;  /* base register for op_self */
   e->k = VNONRELOC;  /* self expression has a fixed register */
   luaK_reserveregs(fs, 2);  /* method and 'self' produced by op_self */
   lua_assert(key->k == VKSTR);
   /* is method name a short string in a valid K index? */
   if (strisshr(key->u.strval) && luaK_exp2K(fs, key)) {
     /* can use 'self' opcode */
     luaK_codeABCk(fs, OP_SELF, base, ereg, key->u.info, 0);
   }
   else {  /* cannot use 'self' opcode; use move+gettable */
     luaK_exp2anyreg(fs, key);  /* put method name in a register */
     luaK_codeABC(fs, OP_MOVE, base + 1, ereg, 0);  /* copy self to base+1 */
     luaK_codeABC(fs, OP_GETTABLE, base, ereg, key->u.info);  /* get method */
   }
   freeexp(fs, key);
 }
 
 
 /*
 ** Create expression 't[k]'. 't' must have its final result already in a
 ** register or upvalue. Upvalues can only be indexed by literal strings.
 ** Keys can be literal strings in the constant table or arbitrary
 ** values in registers.
 */
 void luaK_indexed (FuncState *fs, expdesc *t, expdesc *k) {
   if (k->k == VKSTR)
     str2K(fs, k);
   lua_assert(!hasjumps(t) &&
              (t->k == VLOCAL || t->k == VNONRELOC || t->k == VUPVAL));
   if (t->k == VUPVAL && !isKstr(fs, k))  /* upvalue indexed by non 'Kstr'? */
     luaK_exp2anyreg(fs, t);  /* put it in a register */
   if (t->k == VUPVAL) {
     lu_byte temp = cast_byte(t->u.info);  /* upvalue index */
     lua_assert(isKstr(fs, k));
     t->u.ind.t = temp;  /* (can't do a direct assignment; values overlap) */
     t->u.ind.idx = cast(short, k->u.info);  /* literal short string */
     t->k = VINDEXUP;
   }
   else {
     /* register index of the table */
     t->u.ind.t = cast_byte((t->k == VLOCAL) ? t->u.var.ridx: t->u.info);
     if (isKstr(fs, k)) {
       t->u.ind.idx = cast(short, k->u.info);  /* literal short string */
       t->k = VINDEXSTR;
     }
     else if (isCint(k)) {  /* int. constant in proper range? */
       t->u.ind.idx = cast(short, k->u.ival);
       t->k = VINDEXI;
     }
     else {
       t->u.ind.idx = cast(short, luaK_exp2anyreg(fs, k));  /* register */
       t->k = VINDEXED;
     }
   }
 }
 
 
 /*
 ** Return false if folding can raise an error.
 ** Bitwise operations need operands convertible to integers; division
 ** operations cannot have 0 as divisor.
 */
 static int validop (int op, TValue *v1, TValue *v2) {
   switch (op) {
     case LUA_OPBAND: case LUA_OPBOR: case LUA_OPBXOR:
     case LUA_OPSHL: case LUA_OPSHR: case LUA_OPBNOT: {  /* conversion errors */
       lua_Integer i;
       return (luaV_tointegerns(v1, &i, LUA_FLOORN2I) &&
               luaV_tointegerns(v2, &i, LUA_FLOORN2I));
     }
     case LUA_OPDIV: case LUA_OPIDIV: case LUA_OPMOD:  /* division by 0 */
       return (nvalue(v2) != 0);
     default: return 1;  /* everything else is valid */
   }
 }
 
 
 /*
 ** Try to "constant-fold" an operation; return 1 iff successful.
 ** (In this case, 'e1' has the final result.)
 */
 static int constfolding (FuncState *fs, int op, expdesc *e1,
                                         const expdesc *e2) {
   TValue v1, v2, res;
   if (!tonumeral(e1, &v1) || !tonumeral(e2, &v2) || !validop(op, &v1, &v2))
     return 0;  /* non-numeric operands or not safe to fold */
   luaO_rawarith(fs->ls->L, op, &v1, &v2, &res);  /* does operation */
   if (ttisinteger(&res)) {
     e1->k = VKINT;
     e1->u.ival = ivalue(&res);
   }
   else {  /* folds neither NaN nor 0.0 (to avoid problems with -0.0) */
     lua_Number n = fltvalue(&res);
     if (luai_numisnan(n) || n == 0)
       return 0;
     e1->k = VKFLT;
     e1->u.nval = n;
   }
   return 1;
 }
 
 
 /*
 ** Convert a BinOpr to an OpCode  (ORDER OPR - ORDER OP)
 */
 l_sinline OpCode binopr2op (BinOpr opr, BinOpr baser, OpCode base) {
   lua_assert(baser <= opr &&
             ((baser == OPR_ADD && opr <= OPR_SHR) ||
              (baser == OPR_LT && opr <= OPR_LE)));
   return cast(OpCode, (cast_int(opr) - cast_int(baser)) + cast_int(base));
 }
 
 
 /*
 ** Convert a UnOpr to an OpCode  (ORDER OPR - ORDER OP)
 */
 l_sinline OpCode unopr2op (UnOpr opr) {
   return cast(OpCode, (cast_int(opr) - cast_int(OPR_MINUS)) +
                                        cast_int(OP_UNM));
 }
 
 
 /*
 ** Convert a BinOpr to a tag method  (ORDER OPR - ORDER TM)
 */
 l_sinline TMS binopr2TM (BinOpr opr) {
   lua_assert(OPR_ADD <= opr && opr <= OPR_SHR);
   return cast(TMS, (cast_int(opr) - cast_int(OPR_ADD)) + cast_int(TM_ADD));
 }
 
 
 /*
 ** Emit code for unary expressions that "produce values"
 ** (everything but 'not').
 ** Expression to produce final result will be encoded in 'e'.
 */
 static void codeunexpval (FuncState *fs, OpCode op, expdesc *e, int line) {
   int r = luaK_exp2anyreg(fs, e);  /* opcodes operate only on registers */
   freeexp(fs, e);
   e->u.info = luaK_codeABC(fs, op, 0, r, 0);  /* generate opcode */
   e->k = VRELOC;  /* all those operations are relocatable */
   luaK_fixline(fs, line);
 }
 
 
 /*
 ** Emit code for binary expressions that "produce values"
 ** (everything but logical operators 'and'/'or' and comparison
 ** operators).
 ** Expression to produce final result will be encoded in 'e1'.
 */
 static void finishbinexpval (FuncState *fs, expdesc *e1, expdesc *e2,
                              OpCode op, int v2, int flip, int line,
                              OpCode mmop, TMS event) {
   int v1 = luaK_exp2anyreg(fs, e1);
   int pc = luaK_codeABCk(fs, op, 0, v1, v2, 0);
   freeexps(fs, e1, e2);
   e1->u.info = pc;
   e1->k = VRELOC;  /* all those operations are relocatable */
   luaK_fixline(fs, line);
   luaK_codeABCk(fs, mmop, v1, v2, cast_int(event), flip);  /* metamethod */
   luaK_fixline(fs, line);
 }
 
 
 /*
 ** Emit code for binary expressions that "produce values" over
 ** two registers.
 */
 static void codebinexpval (FuncState *fs, BinOpr opr,
                            expdesc *e1, expdesc *e2, int line) {
   OpCode op = binopr2op(opr, OPR_ADD, OP_ADD);
   int v2 = luaK_exp2anyreg(fs, e2);  /* make sure 'e2' is in a register */
   /* 'e1' must be already in a register or it is a constant */
   lua_assert((VNIL <= e1->k && e1->k <= VKSTR) ||
              e1->k == VNONRELOC || e1->k == VRELOC);
   lua_assert(OP_ADD <= op && op <= OP_SHR);
   finishbinexpval(fs, e1, e2, op, v2, 0, line, OP_MMBIN, binopr2TM(opr));
 }
 
 
 /*
 ** Code binary operators with immediate operands.
 */
 static void codebini (FuncState *fs, OpCode op,
                        expdesc *e1, expdesc *e2, int flip, int line,
                        TMS event) {
   int v2 = int2sC(cast_int(e2->u.ival));  /* immediate operand */
   lua_assert(e2->k == VKINT);
   finishbinexpval(fs, e1, e2, op, v2, flip, line, OP_MMBINI, event);
 }
 
 
 /*
 ** Code binary operators with K operand.
 */
 static void codebinK (FuncState *fs, BinOpr opr,
                       expdesc *e1, expdesc *e2, int flip, int line) {
   TMS event = binopr2TM(opr);
   int v2 = e2->u.info;  /* K index */
   OpCode op = binopr2op(opr, OPR_ADD, OP_ADDK);
   finishbinexpval(fs, e1, e2, op, v2, flip, line, OP_MMBINK, event);
 }
 
 
 /* Try to code a binary operator negating its second operand.
 ** For the metamethod, 2nd operand must keep its original value.
 */
 static int finishbinexpneg (FuncState *fs, expdesc *e1, expdesc *e2,
                              OpCode op, int line, TMS event) {
   if (!isKint(e2))
     return 0;  /* not an integer constant */
   else {
     lua_Integer i2 = e2->u.ival;
     if (!(fitsC(i2) && fitsC(-i2)))
       return 0;  /* not in the proper range */
     else {  /* operating a small integer constant */
       int v2 = cast_int(i2);
       finishbinexpval(fs, e1, e2, op, int2sC(-v2), 0, line, OP_MMBINI, event);
       /* correct metamethod argument */
       SETARG_B(fs->f->code[fs->pc - 1], int2sC(v2));
       return 1;  /* successfully coded */
     }
   }
 }
 
 
 static void swapexps (expdesc *e1, expdesc *e2) {
   expdesc temp = *e1; *e1 = *e2; *e2 = temp;  /* swap 'e1' and 'e2' */
 }
 
 
 /*
 ** Code binary operators with no constant operand.
 */
 static void codebinNoK (FuncState *fs, BinOpr opr,
                         expdesc *e1, expdesc *e2, int flip, int line) {
   if (flip)
     swapexps(e1, e2);  /* back to original order */
   codebinexpval(fs, opr, e1, e2, line);  /* use standard operators */
 }
 
 
 /*
 ** Code arithmetic operators ('+', '-', ...). If second operand is a
 ** constant in the proper range, use variant opcodes with K operands.
 */
 static void codearith (FuncState *fs, BinOpr opr,
                        expdesc *e1, expdesc *e2, int flip, int line) {
   if (tonumeral(e2, NULL) && luaK_exp2K(fs, e2))  /* K operand? */
     codebinK(fs, opr, e1, e2, flip, line);
   else  /* 'e2' is neither an immediate nor a K operand */
     codebinNoK(fs, opr, e1, e2, flip, line);
 }
 
 
 /*
 ** Code commutative operators ('+', '*'). If first operand is a
 ** numeric constant, change order of operands to try to use an
 ** immediate or K operator.
 */
 static void codecommutative (FuncState *fs, BinOpr op,
                              expdesc *e1, expdesc *e2, int line) {
   int flip = 0;
   if (tonumeral(e1, NULL)) {  /* is first operand a numeric constant? */
     swapexps(e1, e2);  /* change order */
     flip = 1;
   }
   if (op == OPR_ADD && isSCint(e2))  /* immediate operand? */
     codebini(fs, OP_ADDI, e1, e2, flip, line, TM_ADD);
   else
     codearith(fs, op, e1, e2, flip, line);
 }
 
 
 /*
 ** Code bitwise operations; they are all commutative, so the function
 ** tries to put an integer constant as the 2nd operand (a K operand).
 */
 static void codebitwise (FuncState *fs, BinOpr opr,
                          expdesc *e1, expdesc *e2, int line) {
   int flip = 0;
   if (e1->k == VKINT) {
     swapexps(e1, e2);  /* 'e2' will be the constant operand */
     flip = 1;
   }
   if (e2->k == VKINT && luaK_exp2K(fs, e2))  /* K operand? */
     codebinK(fs, opr, e1, e2, flip, line);
   else  /* no constants */
     codebinNoK(fs, opr, e1, e2, flip, line);
 }
 
 
 /*
 ** Emit code for order comparisons. When using an immediate operand,
 ** 'isfloat' tells whether the original value was a float.
 */
 static void codeorder (FuncState *fs, BinOpr opr, expdesc *e1, expdesc *e2) {
   int r1, r2;
   int im;
   int isfloat = 0;
   OpCode op;
   if (isSCnumber(e2, &im, &isfloat)) {
     /* use immediate operand */
     r1 = luaK_exp2anyreg(fs, e1);
     r2 = im;
     op = binopr2op(opr, OPR_LT, OP_LTI);
   }
   else if (isSCnumber(e1, &im, &isfloat)) {
     /* transform (A < B) to (B > A) and (A <= B) to (B >= A) */
     r1 = luaK_exp2anyreg(fs, e2);
     r2 = im;
     op = binopr2op(opr, OPR_LT, OP_GTI);
   }
   else {  /* regular case, compare two registers */
     r1 = luaK_exp2anyreg(fs, e1);
     r2 = luaK_exp2anyreg(fs, e2);
     op = binopr2op(opr, OPR_LT, OP_LT);
   }
   freeexps(fs, e1, e2);
   e1->u.info = condjump(fs, op, r1, r2, isfloat, 1);
   e1->k = VJMP;
 }
 
 
 /*
 ** Emit code for equality comparisons ('==', '~=').
 ** 'e1' was already put as RK by 'luaK_infix'.
 */
 static void codeeq (FuncState *fs, BinOpr opr, expdesc *e1, expdesc *e2) {
   int r1, r2;
   int im;
   int isfloat = 0;  /* not needed here, but kept for symmetry */
   OpCode op;
   if (e1->k != VNONRELOC) {
     lua_assert(e1->k == VK || e1->k == VKINT || e1->k == VKFLT);
     swapexps(e1, e2);
   }
   r1 = luaK_exp2anyreg(fs, e1);  /* 1st expression must be in register */
   if (isSCnumber(e2, &im, &isfloat)) {
     op = OP_EQI;
     r2 = im;  /* immediate operand */
   }
   else if (exp2RK(fs, e2)) {  /* 2nd expression is constant? */
     op = OP_EQK;
     r2 = e2->u.info;  /* constant index */
   }
   else {
     op = OP_EQ;  /* will compare two registers */
     r2 = luaK_exp2anyreg(fs, e2);
   }
   freeexps(fs, e1, e2);
   e1->u.info = condjump(fs, op, r1, r2, isfloat, (opr == OPR_EQ));
   e1->k = VJMP;
 }
 
 
 /*
 ** Apply prefix operation 'op' to expression 'e'.
 */
 void luaK_prefix (FuncState *fs, UnOpr opr, expdesc *e, int line) {
   static const expdesc ef = {VKINT, {0}, NO_JUMP, NO_JUMP};
   luaK_dischargevars(fs, e);
   switch (opr) {
     case OPR_MINUS: case OPR_BNOT:  /* use 'ef' as fake 2nd operand */
       if (constfolding(fs, cast_int(opr + LUA_OPUNM), e, &ef))
         break;
       /* else */ /* FALLTHROUGH */
     case OPR_LEN:
       codeunexpval(fs, unopr2op(opr), e, line);
       break;
     case OPR_NOT: codenot(fs, e); break;
     default: lua_assert(0);
   }
 }
 
 
 /*
 ** Process 1st operand 'v' of binary operation 'op' before reading
 ** 2nd operand.
 */
 void luaK_infix (FuncState *fs, BinOpr op, expdesc *v) {
   luaK_dischargevars(fs, v);
   switch (op) {
     case OPR_AND: {
       luaK_goiftrue(fs, v);  /* go ahead only if 'v' is true */
       break;
     }
     case OPR_OR: {
       luaK_goiffalse(fs, v);  /* go ahead only if 'v' is false */
       break;
     }
     case OPR_CONCAT: {
       luaK_exp2nextreg(fs, v);  /* operand must be on the stack */
       break;
     }
     case OPR_ADD: case OPR_SUB:
     case OPR_MUL: case OPR_DIV: case OPR_IDIV:
     case OPR_MOD: case OPR_POW:
     case OPR_BAND: case OPR_BOR: case OPR_BXOR:
     case OPR_SHL: case OPR_SHR: {
       if (!tonumeral(v, NULL))
         luaK_exp2anyreg(fs, v);
       /* else keep numeral, which may be folded or used as an immediate
          operand */
       break;
     }
     case OPR_EQ: case OPR_NE: {
       if (!tonumeral(v, NULL))
         exp2RK(fs, v);
       /* else keep numeral, which may be an immediate operand */
       break;
     }
     case OPR_LT: case OPR_LE:
     case OPR_GT: case OPR_GE: {
       int dummy, dummy2;
       if (!isSCnumber(v, &dummy, &dummy2))
         luaK_exp2anyreg(fs, v);
       /* else keep numeral, which may be an immediate operand */
       break;
     }
     default: lua_assert(0);
   }
 }
 
 /*
 ** Create code for '(e1 .. e2)'.
 ** For '(e1 .. e2.1 .. e2.2)' (which is '(e1 .. (e2.1 .. e2.2))',
 ** because concatenation is right associative), merge both CONCATs.
 */
 static void codeconcat (FuncState *fs, expdesc *e1, expdesc *e2, int line) {
   Instruction *ie2 = previousinstruction(fs);
   if (GET_OPCODE(*ie2) == OP_CONCAT) {  /* is 'e2' a concatenation? */
     int n = GETARG_B(*ie2);  /* # of elements concatenated in 'e2' */
     lua_assert(e1->u.info + 1 == GETARG_A(*ie2));
     freeexp(fs, e2);
     SETARG_A(*ie2, e1->u.info);  /* correct first element ('e1') */
     SETARG_B(*ie2, n + 1);  /* will concatenate one more element */
   }
   else {  /* 'e2' is not a concatenation */
     luaK_codeABC(fs, OP_CONCAT, e1->u.info, 2, 0);  /* new concat opcode */
     freeexp(fs, e2);
     luaK_fixline(fs, line);
   }
 }
 
 
 /*
 ** Finalize code for binary operation, after reading 2nd operand.
 */
 void luaK_posfix (FuncState *fs, BinOpr opr,
                   expdesc *e1, expdesc *e2, int line) {
   luaK_dischargevars(fs, e2);
   if (foldbinop(opr) && constfolding(fs, cast_int(opr + LUA_OPADD), e1, e2))
     return;  /* done by folding */
   switch (opr) {
     case OPR_AND: {
       lua_assert(e1->t == NO_JUMP);  /* list closed by 'luaK_infix' */
       luaK_concat(fs, &e2->f, e1->f);
       *e1 = *e2;
       break;
     }
     case OPR_OR: {
       lua_assert(e1->f == NO_JUMP);  /* list closed by 'luaK_infix' */
       luaK_concat(fs, &e2->t, e1->t);
       *e1 = *e2;
       break;
     }
     case OPR_CONCAT: {  /* e1 .. e2 */
       luaK_exp2nextreg(fs, e2);
       codeconcat(fs, e1, e2, line);
       break;
     }
     case OPR_ADD: case OPR_MUL: {
       codecommutative(fs, opr, e1, e2, line);
       break;
     }
     case OPR_SUB: {
       if (finishbinexpneg(fs, e1, e2, OP_ADDI, line, TM_SUB))
         break; /* coded as (r1 + -I) */
       /* ELSE */
     }  /* FALLTHROUGH */
     case OPR_DIV: case OPR_IDIV: case OPR_MOD: case OPR_POW: {
       codearith(fs, opr, e1, e2, 0, line);
       break;
     }
     case OPR_BAND: case OPR_BOR: case OPR_BXOR: {
       codebitwise(fs, opr, e1, e2, line);
       break;
     }
     case OPR_SHL: {
       if (isSCint(e1)) {
         swapexps(e1, e2);
         codebini(fs, OP_SHLI, e1, e2, 1, line, TM_SHL);  /* I << r2 */
       }
       else if (finishbinexpneg(fs, e1, e2, OP_SHRI, line, TM_SHL)) {
         /* coded as (r1 >> -I) */;
       }
       else  /* regular case (two registers) */
        codebinexpval(fs, opr, e1, e2, line);
       break;
     }
     case OPR_SHR: {
       if (isSCint(e2))
         codebini(fs, OP_SHRI, e1, e2, 0, line, TM_SHR);  /* r1 >> I */
       else  /* regular case (two registers) */
         codebinexpval(fs, opr, e1, e2, line);
       break;
     }
     case OPR_EQ: case OPR_NE: {
       codeeq(fs, opr, e1, e2);
       break;
     }
     case OPR_GT: case OPR_GE: {
       /* '(a > b)' <=> '(b < a)';  '(a >= b)' <=> '(b <= a)' */
       swapexps(e1, e2);
       opr = cast(BinOpr, (opr - OPR_GT) + OPR_LT);
     }  /* FALLTHROUGH */
     case OPR_LT: case OPR_LE: {
       codeorder(fs, opr, e1, e2);
       break;
     }
     default: lua_assert(0);
   }
 }
 
 
 /*
 ** Change line information associated with current position, by removing
 ** previous info and adding it again with new line.
 */
 void luaK_fixline (FuncState *fs, int line) {
   removelastlineinfo(fs);
   savelineinfo(fs, fs->f, line);
 }
 
 
 void luaK_settablesize (FuncState *fs, int pc, int ra, int asize, int hsize) {
   Instruction *inst = &fs->f->code[pc];
   int extra = asize / (MAXARG_vC + 1);  /* higher bits of array size */
   int rc = asize % (MAXARG_vC + 1);  /* lower bits of array size */
   int k = (extra > 0);  /* true iff needs extra argument */
   hsize = (hsize != 0) ? luaO_ceillog2(cast_uint(hsize)) + 1 : 0;
   *inst = CREATE_vABCk(OP_NEWTABLE, ra, hsize, rc, k);
   *(inst + 1) = CREATE_Ax(OP_EXTRAARG, extra);
 }
 
 
 /*
 ** Emit a SETLIST instruction.
 ** 'base' is register that keeps table;
 ** 'nelems' is #table plus those to be stored now;
 ** 'tostore' is number of values (in registers 'base + 1',...) to add to
 ** table (or LUA_MULTRET to add up to stack top).
 */
 void luaK_setlist (FuncState *fs, int base, int nelems, int tostore) {
   lua_assert(tostore != 0);
   if (tostore == LUA_MULTRET)
     tostore = 0;
   if (nelems <= MAXARG_vC)
     luaK_codevABCk(fs, OP_SETLIST, base, tostore, nelems, 0);
   else {
     int extra = nelems / (MAXARG_vC + 1);
     nelems %= (MAXARG_vC + 1);
     luaK_codevABCk(fs, OP_SETLIST, base, tostore, nelems, 1);
     codeextraarg(fs, extra);
   }
   fs->freereg = cast_byte(base + 1);  /* free registers with list values */
 }
 
 
 /*
 ** return the final target of a jump (skipping jumps to jumps)
 */
 static int finaltarget (Instruction *code, int i) {
   int count;
   for (count = 0; count < 100; count++) {  /* avoid infinite loops */
     Instruction pc = code[i];
     if (GET_OPCODE(pc) != OP_JMP)
       break;
     else
       i += GETARG_sJ(pc) + 1;
   }
   return i;
 }
 
 
 /*
 ** Do a final pass over the code of a function, doing small peephole
 ** optimizations and adjustments.
 */
 #include "lopnames.h"
 void luaK_finish (FuncState *fs) {
   int i;
   Proto *p = fs->f;
   for (i = 0; i < fs->pc; i++) {
     Instruction *pc = &p->code[i];
     /* avoid "not used" warnings when assert is off (for 'onelua.c') */
     (void)luaP_isOT; (void)luaP_isIT;
     lua_assert(i == 0 || luaP_isOT(*(pc - 1)) == luaP_isIT(*pc));
     switch (GET_OPCODE(*pc)) {
       case OP_RETURN0: case OP_RETURN1: {
         if (!(fs->needclose || (p->flag & PF_ISVARARG)))
           break;  /* no extra work */
         /* else use OP_RETURN to do the extra work */
         SET_OPCODE(*pc, OP_RETURN);
       }  /* FALLTHROUGH */
       case OP_RETURN: case OP_TAILCALL: {
         if (fs->needclose)
           SETARG_k(*pc, 1);  /* signal that it needs to close */
         if (p->flag & PF_ISVARARG)
           SETARG_C(*pc, p->numparams + 1);  /* signal that it is vararg */
         break;
       }
       case OP_JMP: {
         int target = finaltarget(p->code, i);
         fixjump(fs, i, target);
         break;
       }
       default: break;
     }
   }
 }