codegen.c: refactor `NODE_WHILE` and `NODE_UNTIL`.

mrbgems/mruby-compiler/core/codegen.c

@@ -2268,10 +2268,7 @@ codegen(codegen_scope *s, node *tree, int val)
 
       if (!val) lp->reg = -1;
       lp->pc0 = new_label(s);
-      switch (nint(tree->car->car)) {
-      case NODE_TRUE:
-      case NODE_INT:
-      case NODE_STR:
+      if (true_always(tree->car)) {
         if (nt == NODE_UNTIL) {
           if (val) {
             genop_1(s, OP_LOADNIL, cursp());
@@ -2279,9 +2276,8 @@ codegen(codegen_scope *s, node *tree, int val)
           }
           goto exit;
         }
-        break;
-      case NODE_FALSE:
-      case NODE_NIL:
+      }
+      else if (false_always(tree->car)) {
         if (nt == NODE_WHILE) {
           if (val) {
             genop_1(s, OP_LOADNIL, cursp());
@@ -2289,8 +2285,7 @@ codegen(codegen_scope *s, node *tree, int val)
           }
           goto exit;
         }
-        break;
-      default:
+      }
       codegen(s, tree->car, VAL);
       pop();
       if (nt == NODE_WHILE) {
@@ -2299,8 +2294,6 @@ codegen(codegen_scope *s, node *tree, int val)
       else {
         pos = genjmp2_0(s, OP_JMPIF, cursp(), NOVAL);
       }
-        break;
-      }
       lp->pc1 = new_label(s);
       codegen(s, tree->cdr, NOVAL);
       genjmp(s, OP_JMP, lp->pc0);