Date: Sun, 6 Jan 2019 09:50:32 -0800 From: Brian Neal <brian@aceshardware.com> To: freebsd-hackers@freebsd.org Subject: Re: Speculative: Rust for base system components Message-ID: <e94efcba-3fd3-7d23-cc4a-bcc0af5a8851@aceshardware.com> In-Reply-To: <CAOtMX2jOeAZfpyH1S1N1euAQQZe00nA9JQNjY2qnRB%2BczS9O2g@mail.gmail.com> References: <ca76e5f7-6e59-bd67-144a-90ad66f0252e@metricspace.net> <7d7bc47d-04cf-2f9b-00a3-e3d9d92b3623@aceshardware.com> <72922F2C-9D27-47AA-BB1C-2DA8589CF008@rpi.edu> <92bd5362-d898-aa12-8f3d-9fbe23f38e0c@aceshardware.com> <CAOtMX2gPrpO2O70pnwpU80bXMXo6LB9PCkU3bYw2ToMMnhf%2Bww@mail.gmail.com> <26325c0b-4960-7739-72aa-c31c4e0638d3@aceshardware.com> <CAOtMX2jOeAZfpyH1S1N1euAQQZe00nA9JQNjY2qnRB%2BczS9O2g@mail.gmail.com>
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Of course. But I'm counting like for like. So labels are counted for all languages. And I definitely don't rely on LTO when comparing the efficacy of compiler, especially since the linker can spend lots of time eliminating dead-code (usually single-threaded), which means longer build times. On 1/6/2019 9:17 AM, Alan Somers wrote: > Those 21 lines aren't 21 instructions; you're counting labels. Also, > the first three instructions aren't actually part of the function. > They're dead code, and should be eliminate by LTO. However, Rust > doesn't do LTO when compiling libraries; only when linking > executables. The unwrap logic, etc is also not part of the function. > So in this example, Rust produces only a few more instructions than C. > Also, FYI the Rust expression "0..num" is exclusive on the right. > It's equivalent to C's "for (int i = 0; i < num; i++)", though that > doesn't change the instruction count. > > -Alan
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