Re: [PATCH 1/2] sh: align .bss section padding to 8-byte boundary

[David Laight]

On Wed, 12 Mar 2025 10:47:00 +0100
Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:

> Hi Uros,
> 
> On Wed, 12 Mar 2025 at 09:32, Uros Bizjak <ubizjak@xxxxxxxxx> wrote:
> > On Wed, Mar 12, 2025 at 9:22 AM John Paul Adrian Glaubitz
> > <glaubitz@xxxxxxxxxxxxxxxxxxx> wrote:  
....
> > > OK. FWIW, do you understand what SBSS is for? I couldn't find any explanation
> > > for it.  
> >
> > Small BSS section. The compiler can put data objects under a certain
> > size threshold to the .sbss section. Looking at GCC sh config, sh does
> > not use this section.  

The .sbss (and .sdata) sections are used by some architectures (eg Nios2)
for data that can be accessed using a 16bit offset from a fixed register.
(Although using the register as global register variable generates better code.)
Historically they may have been used for data at the top/bottom of the
addresses space (for the same reason).

There is no reason to just use it for 'small' (eg 8 bytes or less)
data, that is just some empirical default.

I guess they could also be used on cpu like the strongarm for memory
that used the 'small data cache' (useful for screen buffer memory!).

	David