[patch/rfc] align_up, align_down

[Kevin Buettner]

On Sep 12,  4:08pm, Andrew Cagney wrote:

> This patch introduces two utility functions:
> 
> 	align_up (v, n);
> 	align_down (v, n);
> 
> for [re]aligning addresses vis:
> 
> +   addr = align_up (addr, 8); -- VALUE needs 8 byte alignment
> +   write_memory (addr, value, len);
> +   addr += len;
> 
> +   sp = align_down (sp - len, 16); -- Keep SP 16 byte aligned
> +   write_memory (sp, value, len);
> 
> It then goes through and replaces all occurances of round_up / 
> round_down and align_up / align_down with these globals.
> 
> You'll notice that I chose align_XXX rather than round_XXX.  I think 
> this better reflects the intended usage.  I've noticed a lot of code doing:
> 
> 	write_memory (addr, data, len);
> 	addr += round_up (len, 16);
> 
> instead of:
> 
> 	addr = align_up (addr, 16);
> 	write_memory (addr, data, len);
> 	addr += len;
> 
> as the former may not result in ADDR having the required alignment.  The 
> PPC SVr4 Altivec ABI, for instance, switches between 8 and 16 byte 
> alignment making the former code very wrong.
> 
> anyway, thoughts?

Looks good to me...

Kevin