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


From: Richard Henderson
Subject: Re: [PATCH v4 07/45] target/arm: Mark PMULL, FMMLA as non-streaming
Date: Mon, 4 Jul 2022 14:18:12 +0530
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1

On 7/1/22 17:48, Peter Maydell wrote:
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.

Whoops, too right.


r~



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