I don’t know zig syntax, but wouldn’t it be possible to put this common pattern into a macro and simplify it to mostly a lambda on V?

i was having a conversation with a friend recently about simd in zig (which i have recently picked up and been having a pretty good time with). i find that simd writes decently well, though there's a few weird things:

- some builtins purport to work on simd vectors but actually just unpack the vectors and do their work per-element (e.g. running `@sin()` on a `@Vector(4, f32)` will unpack the vector, run `@sin()` 4 times, and then pack it back into a vector).

- a lot of `std.math` is scalar-only (some functions support vectors, though, and i've got a pr open for one of them and plan to do more).

- i'm certainly missing some intrinsics that i get from xmmintrin.h (rcp, rsqrt, few others).

in general though i'm finding it pretty capable.

mitchell, i know you hang around some of these comments sometimes – i noticed that in ghostty you bring in some c++ libs to do the simd heavy lifting for you. any plans to port that to zig? anything missing from the language or libs that's preventing it?

I just do gcc -O3 and get SIMD without having to learn it

In the article, Mitchel mentions how this doesn’t always work. In fact, as someone who’s worked in compiler development, I can say it’s a small miracle when it does work.

Case-in-point, the example in my own post doesn't auto-vectorize with LLVM or GCC at highest optimization levels. Basically, compilers will never auto-vectorize loops with an early loop break afaik.

auto-vectorization is not nearly as good as you would hope it to be.

The best SIMD optimizations likely require changing your data format from AoS to SoA.

Either this or you have to do special tricks like pairwise tree reductions and hand-unroll certain portions of loops.

The one feature in Jonathan Blow's Jai language I really envy is a a single keyword to switch AoS to SoA and visa-versa at comptime

Didn't he drop this feature years ago?

What are AoS and SoA?

Array of Structs and Struct of Arrays https://en.wikipedia.org/wiki/AoS_and_SoA

Array of Structs and Struct of Arrays

And -march=native or at least -march=x86-64-v3 or similar, alternatively identifying relevant functions and manually invoking FMV and uarch specialization via target_clones. Plus non-integer code can generally not be autovectorized in normal-math mode since FP is non-commutative.