Re: check_ext_dependent_givs

[Paolo Bonzini <bonzini at gnu dot org>]

Canqun Yang wrote:
> Hi, all,
>
> Is there anyone familiar with the check routine 
> check_ext_dependent_givs defined loop.c, and give me 
> an example explaining why it is needed.

You should not look at loop.c to modify it, because it will hopefully 
disappear before 4.1.

But basically, that function looks for code like this

   short i;
   long j;
   for (i = 30; i != 10; i++)
     j = (long) i;
     ...

which you cannot transform into

   short i;
   long j;
   for (i = 30, j = 30; i != 10; i++, j++)
     ...

The bulk of the check is in biv_fits_mode_p.

Paolo