Comments on: ASM: What It Can Do For You

By: Kostya

Kostya — Thu, 15 Feb 2007 05:29:47 +0000

And another kind of ASM usage. I once wrote EXE encryption system (not very strong or advanced) and used there assembler for both optimization and for dynamic programming (my program generated .ASM which was feed to NASM and resulted object was injected into EXE). Luckily (for me) it was not complete.

By: astrange

astrange — Thu, 15 Feb 2007 02:51:55 +0000

SSE2 and AltiVec both have C APIs too, of course. Altivec’s is very nice and recommended over ASM, SSE2 is pretty ugly.

I kind of wish ffmpeg didn’t use it so much. The CABAC decoder especially is somewhat weird and messes with the OS X profilers (not to mention that even icc refuses to compile it with frame pointer saving). But the vastly-improved gcc 4.3 isn’t going to be done anytime soon, and I don’t get to code for x86-64, so I guess we’re stuck with it.

By: Multimedia Mike

Multimedia Mike — Wed, 14 Feb 2007 22:53:44 +0000

Thanks for validating what I laid out in the intro of the post, that there are people who might not be entirely up to speed on these concepts. Believe it or not, I felt a little silly writing the post because it felt like I may as well be writing “2 + 2 = 4″. That’s the kind of bubble I live in thanks to multimedia hacking. :-)

BTW, someone pointed out to me privately that I should take the opportunity of this post to dispel another myth of ASM coding: That hand-tooled ASM will always be faster than machine-optimized C. NOT true. For most general-purpose programming, just let the compiler worry about it. It does a good enough job and will probably optimize more than you would care to do by hand. Also, be wary of diminishing returns; you might be able to eek a little more performance out of a hand-optimized ASM routine, but it is probably not worth the effort vs. new features.

By: Adam Ehlers Nyholm Thomsen

Adam Ehlers Nyholm Thomsen — Wed, 14 Feb 2007 22:29:53 +0000

I feel almost ashamed to say this but this was really enlightening for me. Yes I have always heard the legends that hand coding assembly does wonders for speed, but for someone who has never done any assembly programming it was interesting to see where and how hand coding assembly makes things faster. Once again thanks for some interesting posts.