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From: Richard Henderson <richard.henderson@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-arm <qemu-arm@nongnu.org>, QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: [PATCH for-6.2 17/34] target/arm: Implement MVE VMLAS
Date: Sat, 17 Jul 2021 13:40:45 -0700	[thread overview]
Message-ID: <6e31e5da-b4c8-4555-7a70-7d9b4a6e55b1@linaro.org> (raw)
In-Reply-To: <CAFEAcA-o=rC1Zm6JyFECZ_uXndbRurrZdYVWTn9aq=dHXsWJSw@mail.gmail.com>

On 7/17/21 3:06 AM, Peter Maydell wrote:
> On Fri, 16 Jul 2021 at 23:12, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>>
>> On 7/13/21 6:37 AM, Peter Maydell wrote:
>>> Implement the MVE VMLAS insn, which multiplies a vector by a vector
>>> and adds a scalar.
>>>
>>> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
>>> ---
>>>    target/arm/helper-mve.h    |  8 ++++++++
>>>    target/arm/mve.decode      |  3 +++
>>>    target/arm/mve_helper.c    | 31 +++++++++++++++++++++++++++++++
>>>    target/arm/translate-mve.c |  2 ++
>>>    4 files changed, 44 insertions(+)
>> ...
>>
>>> +/* Vector by vector plus scalar */
>>> +#define DO_VMLAS(D, N, M) ((N) * (D) + (M))
>>> +
>>> +DO_2OP_ACC_SCALAR_S(vmlass, DO_VMLAS)
>>> +DO_2OP_ACC_SCALAR_U(vmlasu, DO_VMLAS)
>>
>> This is confusing.  The ARM says
>>
>> # Operations that do not perform
>> # widening are always unsigned (encoded with U=1),
> 
> I have noticed that that text often appears for insns where it doesn't
> really apply. I mostly ignore the text in favour of looking at
> the pseudocode for working out what is supposed to be done.

Yes, but in this case there's nothing about the pseudocode that suggests that sign matters 
at all.  Neither the multiply nor the addition are widening.  So is there really a signed 
VMLAS instruction?


r~



  reply	other threads:[~2021-07-17 20:42 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-13 13:36 [PATCH for-6.2 00/34] target/arm: Third slice of MVE implementation Peter Maydell
2021-07-13 13:36 ` [PATCH for-6.2 01/34] target/arm: Note that we handle VMOVL as a special case of VSHLL Peter Maydell
2021-07-14 17:02   ` Richard Henderson
2021-07-13 13:36 ` [PATCH for-6.2 02/34] target/arm: Print MVE VPR in CPU dumps Peter Maydell
2021-07-15  1:34   ` Richard Henderson
2021-07-13 13:36 ` [PATCH for-6.2 03/34] target/arm: Fix MVE VSLI by 0 and VSRI by <dt> Peter Maydell
2021-07-16 16:27   ` Richard Henderson
2021-07-13 13:36 ` [PATCH for-6.2 04/34] target/arm: Fix signed VADDV Peter Maydell
2021-07-15  1:37   ` Richard Henderson
2021-07-13 13:36 ` [PATCH for-6.2 05/34] target/arm: Fix mask handling for MVE narrowing operations Peter Maydell
2021-07-16 16:29   ` Richard Henderson
2021-07-13 13:36 ` [PATCH for-6.2 06/34] target/arm: Fix 48-bit saturating shifts Peter Maydell
2021-07-16 16:34   ` Richard Henderson
2021-07-16 16:39     ` Peter Maydell
2021-07-13 13:36 ` [PATCH for-6.2 07/34] target/arm: Fix calculation of LTP mask when LR is 0 Peter Maydell
2021-07-16 16:35   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 08/34] target/arm: Fix VPT advance when ECI is non-zero Peter Maydell
2021-07-16 16:44   ` Richard Henderson
2021-07-16 16:58   ` Richard Henderson
2021-07-19 14:16     ` Peter Maydell
2021-07-13 13:37 ` [PATCH for-6.2 09/34] target/arm: Factor out mve_eci_mask() Peter Maydell
2021-07-16 16:48   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 10/34] target/arm: Fix VLDRB/H/W for predicated elements Peter Maydell
2021-07-16 16:58   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 11/34] target/arm: Implement MVE VMULL (polynomial) Peter Maydell
2021-07-16 17:14   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 12/34] target/arm: Implement MVE incrementing/decrementing dup insns Peter Maydell
2021-07-16 19:57   ` Richard Henderson
2021-07-19 14:25     ` Peter Maydell
2021-07-13 13:37 ` [PATCH for-6.2 13/34] target/arm: Factor out gen_vpst() Peter Maydell
2021-07-16 21:04   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 14/34] target/arm: Implement MVE integer vector comparisons Peter Maydell
2021-07-16 21:55   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 15/34] target/arm: Implement MVE integer vector-vs-scalar comparisons Peter Maydell
2021-07-16 21:58   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 16/34] target/arm: Implement MVE VPSEL Peter Maydell
2021-07-16 22:03   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 17/34] target/arm: Implement MVE VMLAS Peter Maydell
2021-07-16 22:11   ` Richard Henderson
2021-07-17 10:06     ` Peter Maydell
2021-07-17 20:40       ` Richard Henderson [this message]
2021-07-20 10:13         ` Peter Maydell
2021-07-13 13:37 ` [PATCH for-6.2 18/34] target/arm: Implement MVE shift-by-scalar Peter Maydell
2021-07-16 22:15   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 19/34] target/arm: Move 'x' and 'a' bit definitions into vmlaldav formats Peter Maydell
2021-07-16 22:16   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 20/34] target/arm: Implement MVE integer min/max across vector Peter Maydell
2021-07-17 20:46   ` Richard Henderson
2021-07-19 15:28     ` Peter Maydell
2021-07-20 18:21       ` Peter Maydell
2021-07-13 13:37 ` [PATCH for-6.2 21/34] target/arm: Implement MVE VABAV Peter Maydell
2021-07-17 20:50   ` Richard Henderson
2021-07-17 22:13     ` Peter Maydell
2021-07-17 22:18       ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 22/34] target/arm: Implement MVE narrowing moves Peter Maydell
2021-07-21 21:45   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 23/34] target/arm: Rename MVEGenDualAccOpFn to MVEGenLongDualAccOpFn Peter Maydell
2021-07-21 21:45   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 24/34] target/arm: Implement MVE VMLADAV and VMLSLDAV Peter Maydell
2021-07-21 22:01   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 25/34] target/arm: Implement MVE VMLA Peter Maydell
2021-07-21 22:03   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 26/34] target/arm: Implement MVE saturating doubling multiply accumulates Peter Maydell
2021-07-21 22:07   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 27/34] target/arm: Implement MVE VQABS, VQNEG Peter Maydell
2021-07-21 22:09   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 28/34] target/arm: Implement MVE VMAXA, VMINA Peter Maydell
2021-07-21 22:12   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 29/34] target/arm: Implement MVE VMOV to/from 2 general-purpose registers Peter Maydell
2021-07-21 22:20   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 30/34] target/arm: Implement MVE VPNOT Peter Maydell
2021-07-21 22:24   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 31/34] target/arm: Implement MVE VCTP Peter Maydell
2021-07-21 22:33   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 32/34] target/arm: Implement MVE scatter-gather insns Peter Maydell
2021-07-22  0:36   ` Richard Henderson
2021-07-22  8:42     ` Peter Maydell
2021-07-13 13:37 ` [PATCH for-6.2 33/34] target/arm: Implement MVE scatter-gather immediate forms Peter Maydell
2021-07-22  0:49   ` Richard Henderson
2021-07-13 13:37 ` [PATCH for-6.2 34/34] target/arm: Implement MVE interleaving loads/stores Peter Maydell
2021-07-22 17:52   ` Richard Henderson

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