| > "Expands to the exact same code everywhere on every imaginable compiler, even toy compilers nobody uses" is not part of the definition of "abstraction". MSVC compiler doesn't do SROA, as far as I know. > What do you think http://www.agner.org/optimize/#vectorclass is then? Have you actually looked at that thing? It's not a Point struct, I can tell you that. There's nothing abstract about it. If you want to take advantage of SIMD fully, you need to lay out your data in a very specific way. A Point {x,y,z} struct doesn't naturally fit a SIMD register. Now, if you're willing to make a lot of assumptions on your compiler, you can do something like this:
http://www.codersnotes.com/notes/maths-lib-2016/ Still, you need to put in the work and the research. No magic. > Yes, it is! It makes your code more readable, and if you're compiling on any production-quality C compiler anywhere your Point class will have the same performance as the raw version. Lower maintenance cost, fewer bugs, same performance. If performance really matters then your abstract solution is almost certainly suboptimal and it's not good engineering practice to use it for the sake of readability. |
Yes, it has since at least 2010 (and probably earlier). See "scalar replacement": https://blogs.msdn.microsoft.com/vcblog/2009/11/02/visual-c-...
> Have you actually looked at that thing? It's not a Point struct, I can tell you that. There's nothing abstract about it.
The Vec classes can be used as Point structs.
> If you want to take advantage of SIMD fully, you need to lay out your data in a very specific way. A Point {x,y,z} struct doesn't naturally fit a SIMD register.
So pad it out to 4 fields, using homogeneous coordinates.
> Now, if you're willing to make a lot of assumptions on your compiler, you can do something like this: http://www.codersnotes.com/notes/maths-lib-2016/
That's not making a lot of assumptions about your compiler. The x87 floating point stack, for example, has been obsolete for a long time.
> If performance really matters then your abstract solution is almost certainly suboptimal and it's not good engineering practice to use it for the sake of readability.
I disagree. Let's look at actual examples. "Almost certainly" suboptimal abstractions are not what we've seen in Rust, for example, which leans on abstractions heavily.