linux-kernel - Re: [PATCH] riscv: avoid enabling vectorized code generation

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Message-ID: <39636675da60fc6c54cc8bbab64ddbac@codethink.co.uk>
Date:   Fri, 16 Dec 2022 19:45:21 +0000
From:   Ben Dooks <ben.dooks@...ethink.co.uk>
To:     Saleem Abdulrasool <abdulras@...gle.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: avoid enabling vectorized code generation



On 2022-12-16 18:50, Saleem Abdulrasool wrote:
> The compiler is free to generate vectorized operations for zero'ing
> memory.  The kernel does not use the vector unit on RISCV, similar to
> architectures such as x86 where we use `-mno-mmx` et al to prevent the
> implicit vectorization.  Perform a similar check for
> `-mno-implicit-float` to avoid this on RISC-V targets.

I'm not sure if we should be emitting either of the vector or floating
point instrucitons in the kernel without explicitly marking the section
of code which is using them such as specific accelerator blocks.

-- 
Ben