Re: [RFC] Support register groups in inline asm

[Andrew Pinski <pinskia at gmail dot com>]

On Tue, Nov 15, 2016 at 9:36 AM, Andrew Senkevich
<andrew.n.senkevich@gmail.com> wrote:
> Hi,
>
> new Intel instructions AVX512_4FMAPS and AVX512_4VNNIW introduce use
> of register groups.
>
> To support register groups feature in inline asm needed some extension
> with new constraints.
>
> Current proposal is the following syntax:
>
> __asm__ (“SMTH %[group], %[single]" :
>                                                             [single] "+x"(v0) :
>                                                             [group]
> "Yg4"(v1),  “1+1"(v2), “1+2"(v3), “1+3"(v4));
>
> where "YgN" constraint specifies group of N consecutive registers
> (which is started from register having number as "0 mod
> 2^ceil(log2(N))"),
> and "1+K" specifies the next registers in the group.
>
> Is this syntax ok? How to implement it?


Have you looked into how AARCH64 back-end handles this via OI, etc.
Like:
/* Oct Int: 256-bit integer mode needed for 32-byte vector arguments.  */
INT_MODE (OI, 32);

/* Opaque integer modes for 3 or 4 Neon q-registers / 6 or 8 Neon d-registers
   (2 d-regs = 1 q-reg = TImode).  */
INT_MODE (CI, 48);
INT_MODE (XI, 64);


And then it implements TARGET_ARRAY_MODE_SUPPORTED_P. target hook?
And the x2 types are defined as a struct of an array like:
typedef struct int8x8x2_t
{
  int8x8_t val[2];
} int8x8x2_t;

Thanks,
Andrew

>
> Any comments or proposals will be appreciated, thanks.
>
>
> --
> WBR,
> Andrew