Re:Re: Unreviewed patch^3

[Geoff Keating <geoffk at apple dot com>]

Hi Andreas,

> 2005-05-11  Andreas Krebbel  <krebbel1@de.ibm.com>
>
>         * local-alloc.c (combine_regs): Adjust reg_offset if regs  
> with different mode
>         sizes are combined on big endian machines.

Firstly, please put a comment above the big chunk of code you added,

> --- 1751,1780 ----
>     int usize, ssize;
>     int sqty;
>
> +   if (WORDS_BIG_ENDIAN
> +       && SCALAR_INT_MODE_P (GET_MODE (setreg))
...

It clearly needs a comment.

Also, about this change:

> -       /* Do not combine registers unless one fits within the  
> other.  */
> -       || (offset > 0 && usize + offset > ssize)
> -       || (offset < 0 && usize + offset < ssize)

Could you explain why you think it's safe to combine two registers  
like your example,

setreg:  (subreg:SI (reg:DI x) 4)
usedreg: (reg:SI y)

It seems to me that it's not safe, because they aren't born or killed  
at the same places.

:REVIEWURL http://gcc.gnu.org/ml/gcc-patches/2005-05/msg01000.html :

Attachment: smime.p7s
Description: S/MIME cryptographic signature