Issue #120: Optimize array construction bytecode.

Use a specialized array initializer that pushes values to the end
of the array instead of using a lot of setprop. This avoids the need
to create a lot of number constants for the array indices.

jscompile.c

@@ -302,17 +302,10 @@ static void cbinary(JF, js_Ast *exp, int opcode)
 
 static void carray(JF, js_Ast *list)
 {
-	int i = 0;
 	while (list) {
-		if (list->a->type != EXP_UNDEF) {
-			emitline(J, F, list->a);
-			emitnumber(J, F, i++);
-			cexp(J, F, list->a);
-			emitline(J, F, list->a);
-			emit(J, F, OP_INITPROP);
-		} else {
-			++i;
-		}
+		emitline(J, F, list->a);
+		cexp(J, F, list->a);
+		emit(J, F, OP_INITARRAY);
 		list = list->b;
 	}
 }

jscompile.h

@@ -38,6 +38,7 @@ enum js_OpCode
 
 	OP_IN,		/* <name> <obj> -- <exists?> */
 
+	OP_INITARRAY,	/* <obj> <val> -- <obj> */
 	OP_INITPROP,	/* <obj> <key> <val> -- <obj> */
 	OP_INITGETTER,	/* <obj> <key> <closure> -- <obj> */
 	OP_INITSETTER,	/* <obj> <key> <closure> -- <obj> */

jsrun.c

@@ -1438,6 +1438,10 @@ static void jsR_run(js_State *J, js_Function *F)
 			js_pushboolean(J, b);
 			break;
 
+		case OP_INITARRAY:
+			js_setindex(J, -2, js_getlength(J, -2));
+			break;
+
 		case OP_INITPROP:
 			obj = js_toobject(J, -3);
 			str = js_tostring(J, -2);

opnames.h

@@ -25,6 +25,7 @@
 "setvar",
 "delvar",
 "in",
+"initarray",
 "initprop",
 "initgetter",
 "initsetter",