Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230714-rust-time-v2-1-f5aed84218c4@asahilina.net> <20230714100525.2192448-1-aliceryhl@google.com>
In-Reply-To: <20230714100525.2192448-1-aliceryhl@google.com>
From:   Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Date:   Sat, 15 Jul 2023 18:59:10 +0200
Message-ID: <CANiq72=NkgtT+mO4YUoqcNx3cXM1G2nJ2Y4rXihdT0paqW2QYA@mail.gmail.com>
Subject: Re: [PATCH v2] rust: time: New module for timekeeping functions
To:     Alice Ryhl <aliceryhl@google.com>
Cc:     lina@asahilina.net, alex.gaynor@gmail.com, asahi@lists.linux.dev,
        bjorn3_gh@protonmail.com, boqun.feng@gmail.com, gary@garyguo.net,
        gbs@canishe.com, heghedus.razvan@protonmail.com,
        jistone@redhat.com, jstultz@google.com,
        linux-kernel@vger.kernel.org, ojeda@kernel.org,
        rust-for-linux@vger.kernel.org, sboyd@kernel.org,
        tglx@linutronix.de, wedsonaf@gmail.com
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Fri, Jul 14, 2023 at 12:05=E2=80=AFPM Alice Ryhl <aliceryhl@google.com> =
wrote:
>
> In that case, you should explicitly use `.wrapping_sub` instead to
> convey your intent.

Also to prevent extra code and panics with `CONFIG_RUST_OVERFLOW_CHECKS=3Dy=
`.

> I guess you could also use `abs_diff`, which takes two i64s and returns
> an u64.

I think `abs_diff` sounds best. It introduces an extra branch in its
implementation from what I see, though...

However, since it is the same branch that Lina does for returning
`None`, it should be getting removed. At least in a quick test, LLVM
generates the same code: https://godbolt.org/z/61rafzx71

Cheers,
Miguel