small optimizations.

lcode.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lcode.c,v 1.5 2000/03/03 20:30:47 roberto Exp roberto $
+** $Id: lcode.c,v 1.8 2000/03/09 13:57:37 roberto Exp roberto $
 ** Code generator for Lua
 ** See Copyright Notice in lua.h
 */
@@ -100,6 +100,28 @@ static void luaK_conc (LexState *ls) {
 }
 
 
+static void luaK_eq (LexState *ls) {
+  Instruction *previous = previous_instruction(ls);
+  if (*previous == CREATE_U(PUSHNIL, 1)) {
+    *previous = CREATE_0(NOTOP);
+    luaK_deltastack(ls, -1);  /* undo effect of PUSHNIL */
+  }
+  else
+    luaK_S(ls, IFEQJMP, 0, -2);
+}
+
+
+static void luaK_neq (LexState *ls) {
+  Instruction *previous = previous_instruction(ls);
+  if (*previous == CREATE_U(PUSHNIL, 1)) {
+    ls->fs->pc--;  /* remove PUSHNIL */
+    luaK_deltastack(ls, -1);  /* undo effect of PUSHNIL */
+  }
+  else
+    luaK_S(ls, IFNEQJMP, 0, -2);
+}
+
+
 void luaK_retcode (LexState *ls, int nlocals, int nexps) {
   Instruction *previous = previous_instruction(ls);
   if (nexps > 0 && GET_OPCODE(*previous) == CALL) {
@@ -116,9 +138,7 @@ static void luaK_pushnil (LexState *ls, int n) {
   Instruction *previous = previous_instruction(ls);
   luaK_deltastack(ls, n);
   switch(GET_OPCODE(*previous)) {
-    case PUSHNIL:
-      SETARG_U(*previous, GETARG_U(*previous)+n);
-      break;
+    case PUSHNIL: SETARG_U(*previous, GETARG_U(*previous)+n); break;
     default: luaK_primitivecode(ls, CREATE_U(PUSHNIL, n));
   }
 }
@@ -281,6 +301,8 @@ static OpCode invertjump (OpCode op) {
     case IFLEJMP: return IFGTJMP;
     case IFGTJMP: return IFLEJMP;
     case IFGEJMP: return IFLTJMP;
+    case IFTJMP: case ONTJMP:  return IFFJMP;
+    case IFFJMP: case ONFJMP:  return IFTJMP;
     default:
       LUA_INTERNALERROR(NULL, "invalid jump instruction");
       return ENDCODE;  /* to avoid warnings */
@@ -288,13 +310,23 @@ static OpCode invertjump (OpCode op) {
 }
 
 
+static void luaK_jump (LexState *ls, OpCode jump) {
+  Instruction *previous = previous_instruction(ls);
+  luaK_deltastack(ls, -1);
+  if (*previous == CREATE_0(NOTOP))
+    *previous = CREATE_S(invertjump(jump), 0);
+  else
+    luaK_primitivecode(ls, CREATE_S(jump, 0));
+}
+
+
 static void insert_last (FuncState *fs, int *list) {
-  int temp = *list;
-  *list = fs->pc-1;
-  if (temp == 0)  /* chain list */
+  int first = *list;
+  *list = fs->pc-1;  /* insert last instruction in the list */
+  if (first == 0)
     SETARG_S(fs->f->code[*list], 0);
   else
-    SETARG_S(fs->f->code[*list], temp-fs->pc);
+    SETARG_S(fs->f->code[*list], first-fs->pc);
 }
 
 
@@ -305,18 +337,18 @@ static void luaK_patchlistaux (LexState *ls, int list, int target,
     for (;;) {
       Instruction *i = &code[list];
       OpCode op = GET_OPCODE(*i);
-      int temp = GETARG_S(*i);
-      if (op == special)
+      int next = GETARG_S(*i);
+      if (op == special)  /* this `op' already has a value */
         SETARG_S(*i, special_target-(list+1));
       else {
-        SETARG_S(*i, target-(list+1));
-        if (op == ONTJMP)
+        SETARG_S(*i, target-(list+1));  /* do the patch */
+        if (op == ONTJMP)  /* remove eventual values */
           SET_OPCODE(*i, IFTJMP);
         else if (op == ONFJMP)
           SET_OPCODE(*i, IFFJMP);
       }
-      if (temp == 0) return;
-      list += temp+1;
+      if (next == 0) return;
+      list += next+1;
     }
   }
 }
@@ -327,15 +359,15 @@ void luaK_patchlist (LexState *ls, int list, int target) {
 }
 
 
-static int has_jumps (FuncState *fs, int list, OpCode ignore) {
+static int need_value (FuncState *fs, int list, OpCode hasvalue) {
   if (list == 0) return 0;
-  else {
+  else {  /* check whether list has a jump without a value */
     Instruction *code = fs->f->code;
     for (;;) {
-      int temp = GETARG_S(code[list]);
-      if (GET_OPCODE(code[list]) != ignore) return 1;
-      else if (temp == 0) return 0;
-      list += temp+1;
+      int next = GETARG_S(code[list]);
+      if (GET_OPCODE(code[list]) != hasvalue) return 1;
+      else if (next == 0) return 0;
+      list += next+1;
     }
   }
 }
@@ -348,12 +380,12 @@ static void concatlists (LexState *ls, int *l1, int l2) {
     FuncState *fs = ls->fs;
     int list = *l1;
     for (;;) {  /* traverse `l1' */
-      int temp = GETARG_S(fs->f->code[list]);
-      if (temp == 0) {  /* end of list? */
+      int next = GETARG_S(fs->f->code[list]);
+      if (next == 0) {  /* end of list? */
         SETARG_S(fs->f->code[list], l2-(list+1));  /* end points to `l2' */
         return;
       }
-      list += temp+1;
+      list += next+1;
     }
   }
 }
@@ -368,7 +400,7 @@ void luaK_goiftrue (LexState *ls, expdesc *v, int keepvalue) {
     SET_OPCODE(*previous, invertjump(GET_OPCODE(*previous)));
   else {
     OpCode jump = keepvalue ? ONFJMP : IFFJMP;
-    luaK_S(ls, jump, 0, -1);
+    luaK_jump(ls, jump);
   }
   insert_last(fs, &v->u.l.f);
   luaK_patchlist(ls, v->u.l.t, luaK_getlabel(ls));
@@ -378,12 +410,12 @@ void luaK_goiftrue (LexState *ls, expdesc *v, int keepvalue) {
 
 void luaK_goiffalse (LexState *ls, expdesc *v, int keepvalue) {
   FuncState *fs = ls->fs;
-  Instruction *previous;
+  Instruction previous;
   discharge1(ls, v);
-  previous = &fs->f->code[fs->pc-1];
-  if (!ISJUMP(GET_OPCODE(*previous))) {
+  previous = fs->f->code[fs->pc-1];
+  if (!ISJUMP(GET_OPCODE(previous))) {
     OpCode jump = keepvalue ? ONTJMP : IFTJMP;
-    luaK_S(ls, jump, 0, -1);
+    luaK_jump(ls, jump);
   }
   insert_last(fs, &v->u.l.t);
   luaK_patchlist(ls, v->u.l.f, luaK_getlabel(ls));
@@ -395,8 +427,8 @@ void luaK_tostack (LexState *ls, expdesc *v, int onlyone) {
   if (discharge(ls, v)) return;
   else {  /* is an expression */
     FuncState *fs = ls->fs;
-    Instruction *previous = &fs->f->code[fs->pc-1];
-    if (!ISJUMP(GET_OPCODE(*previous)) && v->u.l.f == 0 && v->u.l.t == 0) {
+    OpCode previous = GET_OPCODE(fs->f->code[fs->pc-1]);
+    if (!ISJUMP(previous) && v->u.l.f == 0 && v->u.l.t == 0) {
       /* it is an expression without jumps */
       if (onlyone && v->k == VEXP)
         luaK_setcallreturns(ls, 1);  /* call must return 1 value */
@@ -406,25 +438,25 @@ void luaK_tostack (LexState *ls, expdesc *v, int onlyone) {
       int p_nil = 0;  /* position of an eventual PUSHNIL */
       int p_1 = 0;  /* position of an eventual PUSHINT */
       int final;  /* position after whole expression */
-      if (ISJUMP(GET_OPCODE(*previous))) {
-        insert_last(fs, &v->u.l.t);
+      if (ISJUMP(previous)) {
+        insert_last(fs, &v->u.l.t);  /* put `previous' in true list */
         p_nil = luaK_0(ls, PUSHNILJMP, 0);
         p_1 = luaK_S(ls, PUSHINT, 1, 1);
       }
       else {  /* still may need a PUSHNIL or a PUSHINT */
-        int need_nil = has_jumps(fs, v->u.l.f, ONFJMP);  /* needs a PUSHNIL? */
-        int need_1 = has_jumps(fs, v->u.l.t, ONTJMP);  /* needs a PUSHINT? */
+        int need_nil = need_value(fs, v->u.l.f, ONFJMP);
+        int need_1 = need_value(fs, v->u.l.t, ONTJMP);
         if (need_nil && need_1) {
-          luaK_S(ls, JMP, 2, 0);
+          luaK_S(ls, JMP, 2, 0);  /* skip both pushes */
           p_nil = luaK_0(ls, PUSHNILJMP, 0);
-          p_1 = luaK_S(ls, PUSHINT, 1, 1);
+          p_1 = luaK_S(ls, PUSHINT, 1, 0);
         }
         else if (need_nil || need_1) {
-          luaK_S(ls, JMP, 1, 0);
+          luaK_S(ls, JMP, 1, 0);  /* skip one push */
           if (need_nil)
-            p_nil = luaK_0(ls, PUSHNIL, 1);
+            p_nil = luaK_U(ls, PUSHNIL, 1, 0);
           else  /* need_1 */
-            p_1 = luaK_S(ls, PUSHINT, 1, 1);
+            p_1 = luaK_S(ls, PUSHINT, 1, 0);
         }
       }
       final = luaK_getlabel(ls);
@@ -462,7 +494,7 @@ void luaK_infix (LexState *ls, int op, expdesc *v) {
   else if (op == OR)
     luaK_goiffalse(ls, v, 1);
   else
-    luaK_tostack(ls, v, 1);
+    luaK_tostack(ls, v, 1);  /* all other binary operators need a value */
 } 
 
 
@@ -480,7 +512,7 @@ void luaK_posfix (LexState *ls, int op, expdesc *v1, expdesc *v2) {
     concatlists(ls, &v1->u.l.t, v2->u.l.t);
   }
   else {
-    luaK_tostack(ls, v2, 1);  /* `v2' must have a value */
+    luaK_tostack(ls, v2, 1);  /* `v2' must be a value */
     switch (op) {
       case '+': luaK_add(ls); break;
       case '-': luaK_sub(ls); break;
@@ -488,8 +520,8 @@ void luaK_posfix (LexState *ls, int op, expdesc *v1, expdesc *v2) {
       case '/': luaK_0(ls, DIVOP, -1); break;
       case '^': luaK_0(ls, POWOP, -1); break;
       case CONC: luaK_conc(ls); break;
-      case EQ: luaK_S(ls, IFEQJMP, 0, -2); break;
-      case NE: luaK_S(ls, IFNEQJMP, 0, -2); break;
+      case EQ: luaK_eq(ls); break;
+      case NE: luaK_neq(ls); break;
       case '>': luaK_S(ls, IFGTJMP, 0, -2); break;
       case '<': luaK_S(ls, IFLTJMP, 0, -2); break;
       case GE: luaK_S(ls, IFGEJMP, 0, -2); break;

lstring.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lstring.c,v 1.31 1999/12/14 18:42:57 roberto Exp roberto $
+** $Id: lstring.c,v 1.32 2000/03/03 14:58:26 roberto Exp roberto $
 ** String table (keeps all strings handled by Lua)
 ** See Copyright Notice in lua.h
 */
@@ -46,8 +46,9 @@ void luaS_freeall (lua_State *L) {
 
 static unsigned long hash_s (const char *s, long l) {
   unsigned long h = l;  /* seed */
-  while (l--)
-      h = h ^ ((h<<5)+(h>>2)+(unsigned char)*(s++));
+  long step = (l>>6)+1;  /* if string is too long, don't hash all its chars */
+  for (; l>0; l-=step)
+    h = h ^ ((h<<5)+(h>>2)+(unsigned char)*(s++));
   return h;
 }
 
@@ -120,7 +121,8 @@ static void newentry (lua_State *L, stringtable *tb, TaggedString *ts, int h) {
 
 TaggedString *luaS_newlstr (lua_State *L, const char *str, long l) {
   unsigned long h = hash_s(str, l);
-  stringtable *tb = &L->string_root[h%NUM_HASHSTR];
+  stringtable *tb = &L->string_root[(l==0) ? 0 :
+                         ((unsigned int)(str[0]+str[l-1]))&(NUM_HASHSTR-1)];
   int h1 = h&(tb->size-1);
   TaggedString *ts;
   for (ts = tb->hash[h1]; ts; ts = ts->nexthash) {
@@ -134,6 +136,10 @@ TaggedString *luaS_newlstr (lua_State *L, const char *str, long l) {
 }
 
 
+/*
+** uses '%' for one hashing with userdata because addresses are too regular,
+** so two '&' operations would be highly correlated
+*/
 TaggedString *luaS_createudata (lua_State *L, void *udata, int tag) {
   unsigned long h = IntPoint(L, udata);
   stringtable *tb = &L->string_root[(h%NUM_HASHUDATA)+NUM_HASHSTR];

lstring.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lstring.h,v 1.15 1999/12/14 18:42:57 roberto Exp roberto $
+** $Id: lstring.h,v 1.16 2000/03/03 14:58:26 roberto Exp roberto $
 ** String table (keep all strings handled by Lua)
 ** See Copyright Notice in lua.h
 */
@@ -12,7 +12,7 @@
 #include "lstate.h"
 
 
-#define NUM_HASHSTR     31
+#define NUM_HASHSTR     32
 #define NUM_HASHUDATA   31
 #define NUM_HASHS (NUM_HASHSTR+NUM_HASHUDATA)
 

lvm.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lvm.c,v 1.90 2000/03/03 14:58:26 roberto Exp roberto $
+** $Id: lvm.c,v 1.93 2000/03/09 13:57:37 roberto Exp roberto $
 ** Lua virtual machine
 ** See Copyright Notice in lua.h
 */
@@ -360,6 +360,7 @@ StkId luaV_execute (lua_State *L, const Closure *cl, const TProtoFunc *tf,
 
       case PUSHNIL: {
         int n = GETARG_U(i);
+        LUA_ASSERT(L, n>0, "invalid argument");
 		do {
           ttype(top++) = LUA_T_NIL;
 		} while (--n > 0);