logoalt Hacker News

wat10000 • last Wednesday at 4:56 PM • 2 replies • view on HN

I've written assembly in a production environment. I love it and wish I could do more.

But the context where I'm doing it is very different from the context where you had to write a division routine from scratch! We never use assembly where a higher-level language would be good enough. It's only used for things that can't be written in C at all, either because it needs an instruction that the C compiler won't emit, or it involves some special calling convention that C can't express.

However, I read assembly in production all the time. Literally every day on the job. It's absolutely essential for crashes that won't reproduce locally, issues caused by compiler bugs, or extremely sensitive performance work. Now, lots of programmers very rarely have to deal with those sorts of things, but when it comes up, they'll be asking for help from the ones who know this stuff.

Replies

xxpor • last Wednesday at 5:10 PM

+1 on reading.

I hardly consider myself an expert ARM ASM programmer (or even an amateur...), but a baseline level of how to read it even if you have to look up a bunch of instructions every time can be super useful for performance work, especially if you have the abstract computer engineering know how to back it up.

For example, it turns out that gcc 7.3 (for arm64) doesn't optimize

   foo() ? bar() : baz();
the same as

    if (foo()) {
       bar();
    } else {
       baz();
    }
!

The former was compiled into a branchless set of instructions, while the latter had a branch!

ferguess_k • last Wednesday at 5:44 PM

Just curious, what kind of work do you do? Sounds like SRE in FAANG that deals with production systems. I work as a DE and the lowest level thing I have to read is JVM dump from spark. Man I envy you.

➕ show 1 reply