Re: ABI issues with gcc

[Valery Ushakov <uwe%stderr.spb.ru@localhost>]

On Thu, Jan 23, 2014 at 10:42:40 -0500, Christos Zoulas wrote:

> In the process of getting gcc-4.8.x work with NetBSD we encountered an
> issue with sh3, m68k, and vax (maybe more) where spurious SSP warnings
> appear during compilation. I distilled this to a simple test which I have
> submitted to the gcc folks (http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59674)
> 
> Basically this boils down to us having an alignment requirement of an 8
> byte boundary for long long and double, where having a STACK_BOUNDARY
> in the ABI of 4. Gcc does not like that and it does not pre-compute
> where those variables go when it first decides the stack layout of the
> function and it allocates them dynamically in the next pass, leading
> the SSP code to believe this function has a variable stack.
> 
> The choices here are:
> 
>       1. disable ssp for those platforms
>       2. fix gcc so that it deals with this case (the gcc people will
>          probably not take back the changes)
>       3. fix our ABI so for those archs we have a STACK_BOUNDAY of 8

Is it really the case for sh3?

#define STACK_BOUNDARY  BIGGEST_ALIGNMENT
#define BIGGEST_ALIGNMENT  (TARGET_ALIGN_DOUBLE ? 64 : 32)
#define TARGET_ALIGN_DOUBLE ((target_flags & MASK_ALIGN_DOUBLE) != 0

And the only occurence of MASK_ALIGN_DOUBLE is:

  if (TARGET_SH5)
    {
      sh_cpu = PROCESSOR_SH5;
      target_flags |= MASK_ALIGN_DOUBLE;

-uwe