linux-kernel - Re: [PATCH v2] RAS/AMD/ATL: Remove bitwise_xor

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Message-ID: <20251125093529.109c8e1e@pumpkin>
Date: Tue, 25 Nov 2025 09:35:29 +0000
From: david laight <david.laight@...box.com>
To: Nikolay Borisov <nik.borisov@...e.com>
Cc: linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org, bp@...en8.de,
 Yazen.Ghannam@....com
Subject: Re: [PATCH v2] RAS/AMD/ATL: Remove bitwise_xor_bits

On Mon, 24 Nov 2025 10:40:11 +0200
Nikolay Borisov <nik.borisov@...e.com> wrote:

> Both LLVM/GCC support a __builtin_parity function which is functionally
> equivalent to the custom bitwise_xor_bits() one. Let's simplify the code by
> relying on the built-in. No functional changes.
> 

While you've got this code out on the operating table:

- Change all the locals/parameters from u8/u16 to 'unsigned int'.
  It will generate better code.
  Using u8/u16 only makes any sense if you are trying to reduce the
  size of a structure.

- Both col_xor and row_xor are masks (for the parity code).
  So the names are wrong.
  In fact I think all the 'xor' and 'XOR' are incorrectly named.

- How often is 'xor_enable' aka 'mask_enable' set?
  If set most of the time (or the code rarely runs) then if the hardware
  register says 'don't include these values' then just set the row/col
  mask values to zero and let the rest of the code just run through.

	David