Re: Re: [PATCH] RISC-V: Fix V_WHOLE && V_FRACT iterator requirement

[Kito Cheng <kito.cheng@gmail.com>]

Some more detail here:
https://gcc.gnu.org/pipermail/gcc-patches/2023-April/616051.html




On Mon, Jun 12, 2023 at 5:58 PM juzhe.zhong@rivai.ai
<juzhe.zhong@rivai.ai> wrote:
>
> I'd like you to defer to you commit my patch with your test (Jeff has approved my patch, just feel free to commit).
>
> Here is the description:
> We have 3 configuration for "-march"
> 1. zve32*  (TARGET_MIN_VLEN == 32), the LMUL = 1 mode will be VNx4QI, VNx2HI, VNx1SI
> 2. zve64*  (TARGET_MIN_VLEN == 64), the LMUL = 1 mode will be VNx8QI, VNx4HI, VNx2SI
> 3. zve64*_zvl128b  (TARGET_MIN_VLEN >= 128), the LMUL = 1 mode will be VNx16QI, VNx8HI, VNx4SI
>
> We dynamically adjust BYTES_PER_VECTOR according to TARGET_MIN_VLEN.
> For TARGET_MIN_VLEN = 32 (chunk=32), the LMUL = 1 size = (4,4) bytes.
> For TARGET_MIN_VLEN = 64 (chunk=64), the LMUL = 1 size = (8,8) bytes.
> For TARGET_MIN_VLEN >= 128 (chunk=128), the LMUL = 1 size = (16*n,16*n) bytes.
> I have explained it many times.
> https://gcc.gnu.org/pipermail/gcc-patches/2023-March/614935.html
> https://gcc.gnu.org/pipermail/gcc-patches/2023-February/612574.html
>
>
>
>
> juzhe.zhong@rivai.ai
>
> From: Robin Dapp
> Date: 2023-06-12 17:51
> To: 钟居哲; gcc-patches
> CC: rdapp.gcc; kito.cheng; palmer; Jeff Law
> Subject: Re: [PATCH] RISC-V: Fix V_WHOLE && V_FRACT iterator requirement
> > +  (VNx16QI "TARGET_MIN_VLEN <= 128")
> > +  (VNx32QI "TARGET_MIN_VLEN <= 256")
> > +  (VNx64QI "TARGET_MIN_VLEN >= 64 && TARGET_MIN_VLEN <= 512")
> > +  (VNx128QI "TARGET_MIN_VLEN >= 128 && TARGET_MIN_VLEN <= 1024")
> >
> > This not correct, we always use VNx16QI as LMUL = m1 for min_vlen >= 128.
> > Requirement of TARGET_MIN_VLEN <= 128 is incorrect for VNx16QI.
> > VNx32QI,...etc likewise.
>
> Please elaborate.  What happens with a VNx16QI on a target with
> min_vlen == 256?  Is it a full 256-bit vector with only the first half
> populated?  If so, this need documentation either here or somewhere
> else (but with a reference here).
>
> Either you can pick my testcase and amend your patch (plus
> streamline formatting as well adding a proper comment) or I change
> mine.  Your call.
>
> Regards
> Robin
>