Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7;
MIME-Version: 1.0
References: <20230915183707.2707298-1-willy@infradead.org> <20230915183707.2707298-9-willy@infradead.org>
 <CAHk-=wgBUvM7tc70AAvUw+HHOo6Q=jD4FVheFGDCjNaK3OCEGA@mail.gmail.com>
 <ZQT4/gA4vIa/7H6q@casper.infradead.org> <CAHk-=whbj+pVGhJTcQCLhY8KZJNomWOKM=s-GZSpK_G=G4fXEA@mail.gmail.com>
In-Reply-To: <CAHk-=whbj+pVGhJTcQCLhY8KZJNomWOKM=s-GZSpK_G=G4fXEA@mail.gmail.com>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 15 Sep 2023 19:14:52 -0700
Message-ID: <CAHk-=wj+QEzoiUjeUkYqkJe4mcTQCshaAje51PiAuJu+REYxSA@mail.gmail.com>
Subject: Re: [PATCH 08/17] alpha: Implement xor_unlock_is_negative_byte
To:     Matthew Wilcox <willy@infradead.org>
Cc:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-arch@vger.kernel.org, Nicholas Piggin <npiggin@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, 15 Sept 2023 at 19:01, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> No, I think "mov src,dst" is just a pseudo-op for "or src,src,dst",
> there's no actual "mov" instruction, iirc.

Bah. I looked it up. It's actually supposed to be "BIS r31,src,dst".

Where "BIS" is indeed what most sane people call just "or". I think
it's "BIt Set", but the assembler will accept the normal "or" mnemonic
too.

There's BIC ("BIt Clear") too. Also known as "and with complement".

I assume it comes from some VAX background. Or maybe it's just a NIH
thing and alpha wanted to be "special".

              Linus