debug_assert | Simple , flexible and modular assertion macro | Assertion library

It appears you forgot to tell rustc it was allowed to use AVX2 instructions everywhere, so it couldn't inline those functions. Instead, you get a total disaster where only the wrapper functions are compiled as AVX2-using functions, or something like that.

Works fine for me with -O -C target-cpu=skylake-avx512 (https://godbolt.org/z/csY5or43T) so it can inline even the AVX512VL load you used, _mm256_load_epi32¹, and then optimize it into a memory source operand for vpaddd ymm0, ymm0, ymmword ptr [rdi + 4*rax] (AVX2) inside a tight loop.

In GCC / clang, you get an error like "inlining failed in call to always_inline foobar" in this case, instead of working but slow asm. (See this for details). This is something Rust should probably sort out before this is ready for prime time, either be like MSVC and actually inline the instruction into a function using the intrinsic, or refuse to compile like GCC/clang.

Footnote 1: See How to emulate _mm256_loadu_epi32 with gcc or clang? if you didn't mean to use AVX512.

With -O -C target-cpu=skylake (just AVX2), it inlines everything else, including vpaddd ymm, but still calls out to a function that copies 32 bytes from memory to memory with AVX vmovaps. It requires AVX512VL to inline the intrinsic, but later in the optimization process it realizes that with no masking, it's just a 256-bit load it should do without a bloated AVX-512 instruction. It's kinda dumb that Intel even provided a no-masking version of _mm256_mask[z]_loadu_epi32 that requires AVX-512. Or dumb that gcc/clang/rustc consider it an AVX512 intrinsic.