Re: [RFC] Add aarch64 support for ada

[Eric Botcazou <ebotcazou at adacore dot com>]

> The primary bit of rfc here is the hunk that applies to ada/types.h
> with respect to Fat_Pointer.  Given that the Ada type, as defined in
> s-stratt.ads, does not include alignment, I can't imagine why the C
> type should have it.

See gcc-interface/utils.c:finish_fat_pointer_type.

> This causes problems with the AArch64 calling convention, which honors
> this alignment in the set of registers it chooses to pass the struct.
> One can see this difference in create_concat_name vs
> Exp_Dbug.Get_External_Name_With_Suffix.

This should not happen though, since String is passed as a fat pointer too.

> Similarly with the HAVE_GNAT_ALTERNATE_STACK stuff.  There aren't any
> linux hosts that don't support sigaltstack, so why is this
> conditionalized?

Because we don't want to use it if we can avoid it, as this generally makes 
things less robust.  It's mandatory for x86 and x86-64, but I'm not sure why 
PowerPC is in the list.  I'll try and remove it.

Given that aarch32 works without it, I don't think that we should add it for 
aarch64.  This may make some stack checking tests fail, but that's OK since 
there is no stack checking support in the aarch64 back-end AFAIK.

-- 
Eric Botcazou