Re: [PATCH v4 07/45] target/arm: Mark PMULL, FMMLA as non-streaming

[Peter Maydell]

On Tue, 28 Jun 2022 at 05:28, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> Mark these as a non-streaming instructions, which should trap
> if full a64 support is not enabled in streaming mode.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/arm/sme-fa64.decode |  2 --
>  target/arm/translate-sve.c | 18 ++++++++++--------
>  2 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/target/arm/sme-fa64.decode b/target/arm/sme-fa64.decode
> index c25bad5ee5..c75a94e0fc 100644
> --- a/target/arm/sme-fa64.decode
> +++ b/target/arm/sme-fa64.decode
> @@ -58,8 +58,6 @@ FAIL    1100 1110 ---- ---- ---- ---- ---- ----   # 
> Advanced SIMD cryptography e
>  #       --11 1100 --1- ---- ---- ---- ---- --10   # Load/store FP register 
> (register offset)
>  #       --11 1101 ---- ---- ---- ---- ---- ----   # Load/store FP register 
> (scaled imm)
>
> -FAIL    0100 0101 000- ---- 0110 1--- ---- ----   # PMULLB, PMULLT (128b 
> result)

This encoding pattern (as the comment says) covers only the esize = 128 case...

> -TRANS_FEAT(PMULLB, aa64_sve2, do_trans_pmull, a, false)
> -TRANS_FEAT(PMULLT, aa64_sve2, do_trans_pmull, a, true)
> +TRANS_FEAT_NONSTREAMING(PMULLB, aa64_sve2, do_trans_pmull, a, false)
> +TRANS_FEAT_NONSTREAMING(PMULLT, aa64_sve2, do_trans_pmull, a, true)

..but these trans functions cover all the esize values.

In the pseudocode for PMULLB/PMULLT it explicitly does
 if esize < 128 then CheckSVEEnabled(); else CheckNonStreamingSVEEnabled();
so it is definitely intended to distinguish the 128 bit case
from the 16 and 64 bit ones.

thanks
-- PMM