Re: Re: [PATCH 2/3] RISC-V: setmem for RISCV with V extension

[Sergei Lewis]

...oh, and keep the current approach if riscv-autovec-lmul=dynamic.
Makes perfect sense - thanks!

On Mon, Dec 11, 2023 at 3:01 PM 钟居哲  wrote:

> I think we should leave it to user choice.
>
> --param=riscv-autovec-lmul=m1/m2/m4/m8/dynamic.
>
> So use TARGET_MAX_LMUL should be more reasonable.
>
> --
> juzhe.zh...@rivai.ai
>
>
> *From:* Sergei Lewis 
> *Date:* 2023-12-11 22:58
> *To:* juzhe.zh...@rivai.ai
> *CC:* gcc-patches ; Robin Dapp
> ; Kito.cheng ; jeffreyalaw
> 
> *Subject:* Re: [PATCH 2/3] RISC-V: setmem for RISCV with V extension
> The thinking here is that using the largest possible LMUL when we know the
> operation will fit in fewer registers potentially leaves performance on the
> table - indirectly, due to the unnecessarily increased register pressure,
> and also directly, depending on the implementation.
>
> On Mon, Dec 11, 2023 at 10:05 AM juzhe.zh...@rivai.ai <
> juzhe.zh...@rivai.ai> wrote:
>
>> Hi, Thanks for contributing this.
>>
>> +/* Select appropriate LMUL for a single vector operation based on
>> +   byte size of data to be processed.
>> +   On success, return true and populate lmul_out.
>> +   If length_in is too wide for a single vector operation, return false
>> +   and leave lmul_out unchanged.  */
>> +
>> +static bool
>> +select_appropriate_lmul (HOST_WIDE_INT length_in,
>> +HOST_WIDE_INT _out)
>> +{
>>
>> I don't think we need this, you only need to use TARGET_MAX_LMUL
>>
>>
>> --
>> juzhe.zh...@rivai.ai
>>
>

Re: Re: [PATCH 2/3] RISC-V: setmem for RISCV with V extension

[钟居哲]

I think we should leave it to user choice.

--param=riscv-autovec-lmul=m1/m2/m4/m8/dynamic.

So use TARGET_MAX_LMUL should be more reasonable.



juzhe.zh...@rivai.ai
 
From: Sergei Lewis
Date: 2023-12-11 22:58
To: juzhe.zh...@rivai.ai
CC: gcc-patches; Robin Dapp; Kito.cheng; jeffreyalaw
Subject: Re: [PATCH 2/3] RISC-V: setmem for RISCV with V extension
The thinking here is that using the largest possible LMUL when we know the 
operation will fit in fewer registers potentially leaves performance on the 
table - indirectly, due to the unnecessarily increased register pressure, and 
also directly, depending on the implementation.

On Mon, Dec 11, 2023 at 10:05 AM juzhe.zh...@rivai.ai  
wrote:
Hi, Thanks for contributing this.

+/* Select appropriate LMUL for a single vector operation based on
+   byte size of data to be processed.
+   On success, return true and populate lmul_out.
+   If length_in is too wide for a single vector operation, return false
+   and leave lmul_out unchanged.  */
+
+static bool
+select_appropriate_lmul (HOST_WIDE_INT length_in,
+HOST_WIDE_INT _out)
+{
I don't think we need this, you only need to use TARGET_MAX_LMUL




juzhe.zh...@rivai.ai