-fno-type-redefinition-check

don't catch redefinition for local vars. With this option on
    tcc accepts the following code:
    int main()
    {
        int a = 0;
        long a = 0;
    }
    But if you shure there is no problem with your local variables,
    then a compilation speed can be improved if you have a lots of
    the local variables (50000+)

tcc.h

@@ -707,6 +707,7 @@ struct TCCState {
 				   Liuux 2.4.26 can't find initrd when compiled with a new algorithm */
     int dollars_in_identifiers;	/* allows '$' char in indentifiers */
     int normalize_inc_dirs;	/* remove non-existent or duplicate directories from include paths */
+    int no_type_redef_check;    /* no local vars redefinition check */
 
     /* warning switches */
     int warn_write_strings;