{% extends "docframe.html" %} {% block body %}
<div class="page-header">
    <h1>
        Language Spec
        <small>The mini-language at the heart of pathoc and pathod.</small>
    </h1>
</div>

<ul class="nav nav-tabs">
    <li class="active"pre { line-height: 125%; margin: 0; }
td.linenos pre { color: #000000; background-color: #f0f0f0; padding: 0 5px 0 5px; }
span.linenos { color: #000000; background-color: #f0f0f0; padding: 0 5px 0 5px; }
td.linenos pre.special { color: #000000; background-color: #ffffc0; padding: 0 5px 0 5px; }
span.linenos.special { color: #000000; background-color: #ffffc0; padding: 0 5px 0 5px; }
.highlight .hll { background-color: #ffffcc }
.highlight { background: #ffffff; }
.highlight .c { color: #888888 } /* Comment */
.highlight .err { color: #a61717; background-color: #e3d2d2 } /* Error */
.highlight .k { color: #008800; font-weight: bold } /* Keyword */
.highlight .ch { color: #888888 } /* Comment.Hashbang */
.highlight .cm { color: #888888 } /* Comment.Multiline */
.highlight .cp { color: #cc0000; font-weight: bold } /* Comment.Preproc */
.highlight .cpf { color: #888888 } /* Comment.PreprocFile */
.highlight .c1 { color: #888888 } /* Comment.Single */
.highlight .cs { color: #cc0000; font-weight: bold; background-color: #fff0f0 } /* Comment.Special */
.highlight .gd { color: #000000; background-color: #ffdddd } /* Generic.Deleted */
.highlight .ge { font-style: italic } /* Generic.Emph */
.highlight .gr { color: #aa0000 } /* Generic.Error */
.highlight .gh { color: #333333 } /* Generic.Heading */
.highlight .gi { color: #000000; background-color: #ddffdd } /* Generic.Inserted */
.highlight .go { color: #888888 } /* Generic.Output */
.highlight .gp { color: #555555 } /* Generic.Prompt */
.highlight .gs { font-weight: bold } /* Generic.Strong */
.highlight .gu { color: #666666 } /* Generic.Subheading */
.highlight .gt { color: #aa0000 } /* Generic.Traceback */
.highlight .kc { color: #008800; font-weight: bold } /* Keyword.Constant */
.highlight .kd { color: #008800; font-weight: bold } /* Keyword.Declaration */
.highlight .kn { color: #008800; font-weight: bold } /* Keyword.Namespace */
.highlight .kp { color: #008800 } /* Keyword.Pseudo */
.highlight .kr { color: #008800; font-weight: bold } /* Keyword.Reserved */
.highlight .kt { color: #888888; font-weight: bold } /* Keyword.Type */
.highlight .m { color: #0000DD; font-weight: bold } /* Literal.Number */
.highlight .s { color: #dd2200; background-color: #fff0f0 } /* Literal.String */
.highlight .na { color: #336699 } /* Name.Attribute */
.highlight .nb { color: #003388 } /* Name.Builtin */
.highlight .nc { color: #bb0066; font-weight: bold } /* Name.Class */
.highlight .no { color: #003366; font-weight: bold } /* Name.Constant */
.highlight .nd { color: #555555 } /* Name.Decorator */
.highlight .ne { color: #bb0066; font-weight: bold } /* Name.Exception */
.highlight .nf { color: #0066bb; font-weight: bold } /* Name.Function */
.highlight .nl { color: #336699; font-style: italic } /* Name.Label */
.highlight .nn { color: #bb0066; font-weight: bold } /* Name.Namespace */
.highlight .py { color: #336699; font-weight: bold } /* Name.Property */
.highlight .nt { color: #bb0066; font-weight: bold } /* Name.Tag */
.highlight .nv { color: #336699 } /* Name.Variable */
.highlight .ow { color: #008800 } /* Operator.Word */
.highlight .w { color: #bbbbbb } /* Text.Whitespace */
.highlight .mb { color: #0000DD; font-weight: bold } /* Literal.Number.Bin */
.highlight .mf { color: #0000DD; font-weight: bold } /* Literal.Number.Float */
.highlight .mh { color: #0000DD; font-weight: bold } /* Literal.Number.Hex */
.highlight .mi { color: #0000DD; font-weight: bold } /* Literal.Number.Integer */
.highlight .mo { color: #0000DD; font-weight: bold } /* Literal.Number.Oct */
.highlight .sa { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Affix */
.highlight .sb { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Backtick */
.highlight .sc { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Char */
.highlight .dl { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Delimiter */
.highlight .sd { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Doc */
.highlight .s2 { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Double */
.highlight .se { color: #0044dd; background-color: #fff0f0 } /* Literal.String.Escape */
.highlight .sh { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Heredoc */
.highlight .si { color: #3333bb; background-color: #fff0f0 } /* Literal.String.Interpol */
.highlight .sx { color: #22bb22; background-color: #f0fff0 } /* Literal.String.Other */
.highlight .sr { color: #008800; background-color: #fff0ff } /* Literal.String.Regex */
.highlight .s1 { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Single */
.highlight .ss { color: #aa6600; background-color: #fff0f0 } /* Literal.String.Symbol */
.highlight .bp { color: #003388 } /* Name.Builtin.Pseudo */
.highlight .fm { color: #0066bb; font-weight: bold } /* Name.Function.Magic */
.highlight .vc { color: #336699 } /* Name.Variable.Class */
.highlight .vg { color: #dd7700 } /* Name.Variable.Global */
.highlight .vi { color: #3333bb } /* Name.Variable.Instance */
.highlight .vm { color: #336699 } /* Name.Variable.Magic */
.highlight .il { color: #0000DD; font-weight: bold } /* Literal.Number.Integer.Long */
--- a/src/lvm.c
+++ b/src/lvm.c
@@ -31,6 +31,9 @@
 /* limit for table tag-method chains (to avoid loops) */
 #define MAXTAGLOOP	100
 
+#ifdef __GNUC__
+#define COMPUTED_GOTO 1
+#endif
 
 /*
  * If 'obj' is a string, it is tried to be interpreted as a number.
@@ -566,12 +569,63 @@ static inline int arith_mode( const TVal
     ARITH_OP1_END
 #endif
 
+#ifdef COMPUTED_GOTO
+#define OPCODE_TARGET(op) DO_OP_##op:
+#define CALL_OPCODE(op) goto *opcodes[op];
+#define OPCODE_PTR(op) [OP_##op] = &&DO_OP_##op
+#else
+#define OPCODE_TARGET(op) case OP_##op:
+#define CALL_OPCODE(op) switch (op)
+#endif
+
 
 void luaV_execute (lua_State *L, int nexeccalls) {
   LClosure *cl;
   StkId base;
   TValue *k;
   const Instruction *pc;
+#ifdef COMPUTED_GOTO
+  static const void *opcodes[] = {
+   OPCODE_PTR(MOVE),
+   OPCODE_PTR(LOADK),
+   OPCODE_PTR(LOADBOOL),
+   OPCODE_PTR(LOADNIL),
+   OPCODE_PTR(GETUPVAL),
+   OPCODE_PTR(GETGLOBAL),
+   OPCODE_PTR(GETTABLE),
+   OPCODE_PTR(SETGLOBAL),
+   OPCODE_PTR(SETUPVAL),
+   OPCODE_PTR(SETTABLE),
+   OPCODE_PTR(NEWTABLE),
+   OPCODE_PTR(SELF),
+   OPCODE_PTR(ADD),
+   OPCODE_PTR(SUB),
+   OPCODE_PTR(MUL),
+   OPCODE_PTR(DIV),
+   OPCODE_PTR(MOD),
+   OPCODE_PTR(POW),
+   OPCODE_PTR(UNM),
+   OPCODE_PTR(NOT),
+   OPCODE_PTR(LEN),
+   OPCODE_PTR(CONCAT),
+   OPCODE_PTR(JMP),
+   OPCODE_PTR(EQ),
+   OPCODE_PTR(LT),
+   OPCODE_PTR(LE),
+   OPCODE_PTR(TEST),
+   OPCODE_PTR(TESTSET),
+   OPCODE_PTR(CALL),
+   OPCODE_PTR(TAILCALL),
+   OPCODE_PTR(RETURN),
+   OPCODE_PTR(FORLOOP),
+   OPCODE_PTR(FORPREP),
+   OPCODE_PTR(TFORLOOP),
+   OPCODE_PTR(SETLIST),
+   OPCODE_PTR(CLOSE),
+   OPCODE_PTR(CLOSURE),
+   OPCODE_PTR(VARARG)
+  };
+#endif
  reentry:  /* entry point */
   lua_assert(isLua(L->ci));
   pc = L->savedpc;
@@ -596,33 +650,33 @@ void luaV_execute (lua_State *L, int nex
     lua_assert(base == L->base && L->base == L->ci->base);
     lua_assert(base <= L->top && L->top <= L->stack + L->stacksize);
     lua_assert(L->top == L->ci->top || luaG_checkopenop(i));
-    switch (GET_OPCODE(i)) {
-      case OP_MOVE: {
+    CALL_OPCODE(GET_OPCODE(i)) {
+      OPCODE_TARGET(MOVE) {
         setobjs2s(L, ra, RB(i));
         continue;
       }
-      case OP_LOADK: {
+      OPCODE_TARGET(LOADK) {
         setobj2s(L, ra, KBx(i));
         continue;
       }
-      case OP_LOADBOOL: {
+      OPCODE_TARGET(LOADBOOL) {
         setbvalue(ra, GETARG_B(i));
         if (GETARG_C(i)) pc++;  /* skip next instruction (if C) */
         continue;
       }
-      case OP_LOADNIL: {
+      OPCODE_TARGET(LOADNIL) {
         TValue *rb = RB(i);
         do {
           setnilvalue(rb--);
         } while (rb >= ra);
         continue;
       }
-      case OP_GETUPVAL: {
+      OPCODE_TARGET(GETUPVAL) {
         int b = GETARG_B(i);
         setobj2s(L, ra, cl->upvals[b]->v);
         continue;
       }
-      case OP_GETGLOBAL: {
+      OPCODE_TARGET(GETGLOBAL) {
         TValue g;
         TValue *rb = KBx(i);
         sethvalue(L, &g, cl->env);
@@ -630,88 +684,88 @@ void luaV_execute (lua_State *L, int nex
         Protect(luaV_gettable(L, &g, rb, ra));
         continue;
       }
-      case OP_GETTABLE: {
+      OPCODE_TARGET(GETTABLE) {
         Protect(luaV_gettable(L, RB(i), RKC(i), ra));
         continue;
       }
-      case OP_SETGLOBAL: {
+      OPCODE_TARGET(SETGLOBAL) {
         TValue g;
         sethvalue(L, &g, cl->env);
         lua_assert(ttisstring(KBx(i)));
         Protect(luaV_settable(L, &g, KBx(i), ra));
         continue;
       }
-      case OP_SETUPVAL: {
+      OPCODE_TARGET(SETUPVAL) {
         UpVal *uv = cl->upvals[GETARG_B(i)];
         setobj(L, uv->v, ra);
         luaC_barrier(L, uv, ra);
         continue;
       }
-      case OP_SETTABLE: {
+      OPCODE_TARGET(SETTABLE) {
         Protect(luaV_settable(L, ra, RKB(i), RKC(i)));
         continue;
       }
-      case OP_NEWTABLE: {
+      OPCODE_TARGET(NEWTABLE) {
         int b = GETARG_B(i);
         int c = GETARG_C(i);
         sethvalue(L, ra, luaH_new(L, luaO_fb2int(b), luaO_fb2int(c)));
         Protect(luaC_checkGC(L));
         continue;
       }
-      case OP_SELF: {
+      OPCODE_TARGET(SELF) {
         StkId rb = RB(i);
         setobjs2s(L, ra+1, rb);
         Protect(luaV_gettable(L, rb, RKC(i), ra));
         continue;
       }
-      case OP_ADD: {
+      OPCODE_TARGET(ADD) {
         TValue *rb = RKB(i), *rc= RKC(i);
         arith_op_continue( luai_numadd, try_addint, luai_vectadd );
         Protect(Arith(L, ra, rb, rc, TM_ADD)); \
         continue;
       }
-      case OP_SUB: {
+      OPCODE_TARGET(SUB) {
         TValue *rb = RKB(i), *rc= RKC(i);
         arith_op_continue( luai_numsub, try_subint, luai_vectsub );
         Protect(Arith(L, ra, rb, rc, TM_SUB));
         continue;
       }
-      case OP_MUL: {
+      OPCODE_TARGET(MUL) {
         TValue *rb = RKB(i), *rc= RKC(i);
         arith_op_continue(luai_nummul, try_mulint, luai_vectmul);
         Protect(Arith(L, ra, rb, rc, TM_MUL));
         continue;
       }
-      case OP_DIV: {
+      OPCODE_TARGET(DIV) {
         TValue *rb = RKB(i), *rc= RKC(i);
         arith_op_continue(luai_numdiv, try_divint, luai_vectdiv);
         Protect(Arith(L, ra, rb, rc, TM_DIV));
         continue;
       }
-      case OP_MOD: {
+      OPCODE_TARGET(MOD) {
         TValue *rb = RKB(i), *rc= RKC(i);
         arith_op_continue_scalar(luai_nummod, try_modint);  /* scalars only */
         Protect(Arith(L, ra, rb, rc, TM_MOD));
         continue;
       }
-      case OP_POW: {
+      OPCODE_TARGET(POW) {
         TValue *rb = RKB(i), *rc= RKC(i);
         arith_op_continue(luai_numpow, try_powint, luai_vectpow);
         Protect(Arith(L, ra, rb, rc, TM_POW));
         continue;
       }
-      case OP_UNM: {
+      OPCODE_TARGET(UNM) {
         TValue *rb = RB(i);
         arith_op1_continue(luai_numunm, try_unmint, luai_vectunm);
         Protect(Arith(L, ra, rb, rb, TM_UNM));
         continue;
       }
-      case OP_NOT: {
+      OPCODE_TARGET(NOT) {
         int res = l_isfalse(RB(i));  /* next assignment may change this value */
         setbvalue(ra, res);
         continue;
       }
-      case OP_LEN: {
+      OPCODE_TARGET(LEN) {
         const TValue *rb = RB(i);
         switch (ttype(rb)) {
           case LUA_TTABLE: {
@@ -731,18 +785,18 @@ void luaV_execute (lua_State *L, int nex
         }
         continue;
       }
-      case OP_CONCAT: {
+      OPCODE_TARGET(CONCAT) {
         int b = GETARG_B(i);
         int c = GETARG_C(i);
         Protect(luaV_concat(L, c-b+1, c); luaC_checkGC(L));
         setobjs2s(L, RA(i), base+b);
         continue;
       }
-      case OP_JMP: {
+      OPCODE_TARGET(JMP) {
         dojump(L, pc, GETARG_sBx(i));
         continue;
       }
-      case OP_EQ: {
+      OPCODE_TARGET(EQ) {
         TValue *rb = RKB(i);
         TValue *rc = RKC(i);
         Protect(
@@ -752,7 +806,7 @@ void luaV_execute (lua_State *L, int nex
         pc++;
         continue;
       }
-      case OP_LT: {
+      OPCODE_TARGET(LT) {
         Protect(
           if (luaV_lessthan(L, RKB(i), RKC(i)) == GETARG_A(i))
             dojump(L, pc, GETARG_sBx(*pc));
@@ -760,7 +814,7 @@ void luaV_execute (lua_State *L, int nex
         pc++;
         continue;
       }
-      case OP_LE: {
+      OPCODE_TARGET(LE) {
         Protect(
           if (lessequal(L, RKB(i), RKC(i)) == GETARG_A(i))
             dojump(L, pc, GETARG_sBx(*pc));
@@ -768,13 +822,13 @@ void luaV_execute (lua_State *L, int nex
         pc++;
         continue;
       }
-      case OP_TEST: {
+      OPCODE_TARGET(TEST) {
         if (l_isfalse(ra) != GETARG_C(i))
           dojump(L, pc, GETARG_sBx(*pc));
         pc++;
         continue;
       }
-      case OP_TESTSET: {
+      OPCODE_TARGET(TESTSET) {
         TValue *rb = RB(i);
         if (l_isfalse(rb) != GETARG_C(i)) {
           setobjs2s(L, ra, rb);
@@ -783,7 +837,7 @@ void luaV_execute (lua_State *L, int nex
         pc++;
         continue;
       }
-      case OP_CALL: {
+      OPCODE_TARGET(CALL) {
         int b = GETARG_B(i);
         int nresults = GETARG_C(i) - 1;
         if (b != 0) L->top = ra+b;  /* else previous instruction set top */
@@ -804,7 +858,7 @@ void luaV_execute (lua_State *L, int nex
           }
         }
       }
-      case OP_TAILCALL: {
+      OPCODE_TARGET(TAILCALL) {
         int b = GETARG_B(i);
         if (b != 0) L->top = ra+b;  /* else previous instruction set top */
         L->savedpc = pc;
@@ -836,7 +890,7 @@ void luaV_execute (lua_State *L, int nex
           }
         }
       }
-      case OP_RETURN: {
+      OPCODE_TARGET(RETURN) {
         int b = GETARG_B(i);
         if (b != 0) L->top = ra+b-1;
         if (L->openupval) luaF_close(L, base);
@@ -851,7 +905,7 @@ void luaV_execute (lua_State *L, int nex
           goto reentry;
         }
       }
-      case OP_FORLOOP: {
+      OPCODE_TARGET(FORLOOP) {
         /* If start,step and limit are all integers, we don't need to check
          * against overflow in the looping.
          */
@@ -879,7 +933,7 @@ void luaV_execute (lua_State *L, int nex
         }
         continue;
       }
-      case OP_FORPREP: {
+      OPCODE_TARGET(FORPREP) {
         const TValue *init = ra;
         const TValue *plimit = ra+1;
         const TValue *pstep = ra+2;
@@ -902,7 +956,7 @@ void luaV_execute (lua_State *L, int nex
         dojump(L, pc, GETARG_sBx(i));
         continue;
       }
-      case OP_TFORLOOP: {
+      OPCODE_TARGET(TFORLOOP) {
         StkId cb = ra + 3;  /* call base */
         setobjs2s(L, cb+2, ra+2);
         setobjs2s(L, cb+1, ra+1);
@@ -918,7 +972,7 @@ void luaV_execute (lua_State *L, int nex
         pc++;
         continue;
       }
-      case OP_SETLIST: {
+      OPCODE_TARGET(SETLIST) {
         int n = GETARG_B(i);
         int c = GETARG_C(i);
         int last;
@@ -940,11 +994,11 @@ void luaV_execute (lua_State *L, int nex
         }
         continue;
       }
-      case OP_CLOSE: {
+      OPCODE_TARGET(CLOSE) {
         luaF_close(L, ra);
         continue;
       }
-      case OP_CLOSURE: {
+      OPCODE_TARGET(CLOSURE) {
         Proto *p;
         Closure *ncl;
         int nup, j;
@@ -964,7 +1018,7 @@ void luaV_execute (lua_State *L, int nex
         Protect(luaC_checkGC(L));
         continue;
       }
-      case OP_VARARG: {
+      OPCODE_TARGET(VARARG) {
         int b = GETARG_B(i) - 1;
         int j;
         CallInfo *ci = L->ci;