On Thu, Feb 20, 2014 at 06:46:21PM +0800, lin zuojian wrote:
> Oh, you may think my patch have not violated STRICT_ALIGNMENT.My patch
> doesn't realign stack_pointer,but virtual_stack_vars,although they may
> share the same position mostly.
> As you can see,the code emitted just make the stack 8 bytes aligned.
>
> > You mean that for the prologues right now on ARM we emit unaligned
> > store insns during expansion and that they are later peepholed into
> > aligned stores?
> Yes.Because SImode is aligned to 4 bytes ,and str is considered aligned
> to 4 bytes on all ARM machine,so gcc doesn't consider itself emitting
> the unaligned str instructions in the first place.Of course aligned str
> can be peepholed into aligned str multiple.
ARM is a STRICT_ALIGNMENT target, I was suggesting that you do the changes
you want to do only for STRICT_ALIGNMENT targets. They are not desirable
for !STRICT_ALIGNMENT targets like i?86/x86_64 (or say ppc/ppc64 unless
strict alignment is requested by compielr option).
Jakub
