small optimization for sizes of array constructors

lobject.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lobject.c,v 1.94 2002/12/04 17:38:31 roberto Exp roberto $
+** $Id: lobject.c,v 1.95 2003/01/27 13:00:43 roberto Exp roberto $
 ** Some generic functions over Lua objects
 ** See Copyright Notice in lua.h
 */
@@ -30,6 +30,20 @@
 const TObject luaO_nilobject = {LUA_TNIL, {NULL}};
 
 
+/*
+** converts an integer to a "floating point byte", represented as
+** (mmmmmxxx), where the real value is (xxx) * 2^(mmmmm)
+*/
+int luaO_int2fb (unsigned int x) {
+  int m = 0;  /* mantissa */
+  while (x >= (1<<3)) {
+    x = (x+1) >> 1;
+    m++;
+  }
+  return (m << 3) | cast(int, x);
+}
+
+
 int luaO_log2 (unsigned int x) {
   static const lu_byte log_8[255] = {
     0,

lobject.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lobject.h,v 1.156 2002/12/19 11:11:55 roberto Exp roberto $
+** $Id: lobject.h,v 1.157 2003/02/11 10:46:24 roberto Exp roberto $
 ** Type definitions for Lua objects
 ** See Copyright Notice in lua.h
 */
@@ -323,7 +323,8 @@ typedef struct Table {
 extern const TObject luaO_nilobject;
 
 int luaO_log2 (unsigned int x);
-
+int luaO_int2fb (unsigned int x);
+#define fb2int(x)	(((x) & 7) << ((x) >> 3))
 
 int luaO_rawequalObj (const TObject *t1, const TObject *t2);
 int luaO_str2d (const char *s, lua_Number *result);

lparser.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lparser.c,v 1.204 2003/02/11 10:46:24 roberto Exp roberto $
+** $Id: lparser.c,v 1.205 2003/02/11 10:49:53 roberto Exp roberto $
 ** Lua Parser
 ** See Copyright Notice in lua.h
 */
@@ -515,8 +515,7 @@ static void constructor (LexState *ls, expdesc *t) {
   } while (testnext(ls, ',') || testnext(ls, ';'));
   check_match(ls, '}', '{', line);
   lastlistfield(fs, &cc);
-  if (cc.na > 0)
-    SETARG_B(fs->f->code[pc], luaO_log2(cc.na-1)+2); /* set initial table size */
+  SETARG_B(fs->f->code[pc], luaO_int2fb(cc.na)); /* set initial array size */
   SETARG_C(fs->f->code[pc], luaO_log2(cc.nh)+1);  /* set initial table size */
 }
 

ltests.c

@@ -1,5 +1,5 @@
 /*
-** $Id: ltests.c,v 1.151 2003/01/29 10:27:53 roberto Exp roberto $
+** $Id: ltests.c,v 1.152 2003/02/10 17:31:13 roberto Exp roberto $
 ** Internal Module for Debugging of the Lua Implementation
 ** See Copyright Notice in lua.h
 */
@@ -512,6 +512,13 @@ static int log2_aux (lua_State *L) {
   return 1;
 }
 
+static int int2fb_aux (lua_State *L) {
+  int b = luaO_int2fb(luaL_checkint(L, 1));
+  lua_pushnumber(L, b);
+  lua_pushnumber(L, fb2int(b));
+  return 2;
+}
+
 
 static int test_do (lua_State *L) {
   const char *p = luaL_checkstring(L, 1);
@@ -790,6 +797,7 @@ static const struct luaL_reg tests_funcs[] = {
   {"closestate", closestate},
   {"doremote", doremote},
   {"log2", log2_aux},
+  {"int2fb", int2fb_aux},
   {"totalmem", mem_query},
   {"resume", coresume},
   {"setyhook", setyhook},

lvm.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lvm.c,v 1.274 2003/01/27 15:12:52 roberto Exp roberto $
+** $Id: lvm.c,v 1.275 2003/02/11 10:46:24 roberto Exp roberto $
 ** Lua virtual machine
 ** See Copyright Notice in lua.h
 */
@@ -495,7 +495,7 @@ StkId luaV_execute (lua_State *L) {
       }
       case OP_NEWTABLE: {
         int b = GETARG_B(i);
-        if (b > 0) b = twoto(b-1);
+        b = fb2int(b);
         sethvalue(ra, luaH_new(L, b, GETARG_C(i)));
         luaC_checkGC(L);
         break;