Re: [ARM] Fix PR middle-end/65958

[Eric Botcazou <ebotcazou@adacore.com>]

> Unless there really is common code between the two patches, this should
> be separated out into two posts, one for ARM and one for AArch64.

The ARM bits were approved by Ramana and installed right away.

> Hmm, so if PROBE_INTERVAL != 4096 we barf!

Yes, but that's not usual, ARM and SPARC have it too, 4096 happens to be the 
limit of reg+off addressing mode on several architectures.

> While that's safe and probably right for Linux, on some OSes there might
> be a minimum page size of 16k or even 64k.  It would be nice if we could
> support that.

OK, but we cannot test anything at the moment.

> Ug!  Manifest constants should be moved to pre-defines.
> PROBE_STACK_BASE_REG?

OK.

> > +
> > +  /* The following code uses indexed address calculation on FIRST.  */
> > +  gcc_assert ((first % 4096) == 0);
> 
> where's 4096 come from?

It's the same constraint as above:

#if (PROBE_INTERVAL % 4096) != 0
#error Cannot use indexed address calculation for stack probing
#endif

to be able to use the 12-bit shifted immediate instructions. 

> More manifest constants.

Yeah, consistency first. ;-)

> This should be annotated with the sequence length.

OK, thanks for the review, I'll adjust.

-- 
Eric Botcazou