Re: [PATCH] Modify Aarch64 prologue analyzer to accept 128-bit registers

[Andrew Pinski <pinskia@gmail.com>]

On Mon, Nov 13, 2017 at 9:28 AM, pcarroll@codesourcery.com
<pcarroll@codesourcery.com> wrote:
> GDB has a routine, aarch64_analyze_prologue, that looks through a function's prologue, to see how it affects the stack.
> This was changed for Bugzilla #20682 to add support for recognizing the 'stp' instruction with floating-point registers.
> That patch worked when 64-bit floating-point registers are used in a function prologue.
> However, it is also possible to specify 128-bit floating-point registers with the 'stp' instruction.
> My patch extends that function so it works for either 64-bit or 128-bit floating-point registers.
> The patch takes care of tracking the appropriate memory locations that would be affected by the use of either size of register.
>
> The assumption is that it is not important to know whether the register being saved is 64-bits or 128-bits in size, as long as the memory is tracked appropriately.
> Instead, it is only important to know that a floating-point register (D) was being stored, rather than a normal register (X).
> That behavior is unchanged.

Hmm,  The normal elf aarch64 ABI says only 64bits is saved.  Is there
another ABI which says 128bits of the SIMD register is saved?

Thanks,
Andrew

>
> 2017-11-10  Paul Carroll  <pcarroll@codesourcery.com>
>
>              * aarch64-tdep.c (aarch64_analyze_prologue):  Added support for
>              128-bit registers with the 'stp' instruction.