RE: Re: [PATCH V5] RISC-V: Using merge approach to optimize repeating sequence in vec_init

["Li, Pan2" <pan2.li@intel.com>]

Hi Kito,

Update the PATCH v6 with refactored framework as below, thanks for comments.

https://gcc.gnu.org/pipermail/gcc-patches/2023-May/619536.html

Pan

-----Original Message-----
From: Gcc-patches <gcc-patches-bounces+pan2.li=intel.com@gcc.gnu.org> On Behalf Of Kito Cheng via Gcc-patches
Sent: Wednesday, May 17, 2023 11:52 AM
To: juzhe.zhong@rivai.ai
Cc: gcc-patches <gcc-patches@gcc.gnu.org>; palmer <palmer@dabbelt.com>; jeffreyalaw <jeffreyalaw@gmail.com>
Subject: Re: Re: [PATCH V5] RISC-V: Using merge approach to optimize repeating sequence in vec_init

On Wed, May 17, 2023 at 11:36 AM juzhe.zhong@rivai.ai <juzhe.zhong@rivai.ai> wrote:
>
> >> Does it means we assume inner_int_mode is DImode? (because sizeof 
> >> (uint64_t)) or it should be something like `for (unsigned int i = 
> >> 0; i < (GET_MODE_SIZE(inner_int_mode ()) * 8 / npatterns ()); i++)` ?
> No, sizeof (uint64_t) means uint64_t mask = 0;

+  return gen_int_mode (mask, inner_int_mode ());
And we expect the uint64_t mask can always be put into inner_int_mode ()?
If not, why do we fill up all 64 bits?

>
> >> Do you mind give more comment about this? what it checked and what it did?
> The reason we use known_gt (GET_MODE_SIZE (dup_mode), 
> BYTES_PER_RISCV_VECTOR) since we want are using vector integer mode to 
> generate the mask for example we generate 0b01010101010101.... mask, we should use a scalar register holding value = 0b010101010...
> Then vmv.v.x into a vector,then this vector will be used as a mask.
>
> >> Why this only hide in else? I guess I have this question is because 
> >> I don't fully understand the logic of the if condition?
>
> Since we can't vector floting-point instruction to generate a mask.

I don't get why it's not something like below?

if (known_gt (GET_MODE_SIZE (dup_mode), BYTES_PER_RISCV_VECTOR)) { ...
}
if (FLOAT_MODE_P (dup_mode))
{
...
}



>
> >> nit: builder.inner_mode () rather than GET_MODE_INNER (dup_mode)?
>
> They are the same. I can change it using GET_MODE_INNER
>
> >> And I would like have more commnet to explain why we need force_reg here.
> Since it will creat ICE.

But why? And why can it be resolved by force_reg? you need few more comment in the code