[WIP] Add intel simd #1703

1. 
   Raimo33 commented at 11:26 am on July 18, 2025: none

   This adds sse2 and avx2 support to the library in general, as discussed in #1700, wherever it yields an improvement as per the benchmarks.

   arm has different SIMD instruction set; it would be nice to have a separate PR implementing that as well. Maybe after this is merged…

   Tasks:

   • Add 2 CI/CD flows with permutations of -msse2, -mno-sse2 when building for amd32
   • Add 4 CI/CD flows with permutations of -mavx2, -msse2, -mno-avx2, -mno-sse2 when building for amd64
   • Precompute vectors at startup (the ones marked with TODO: precompute )

   Test & Benchmark

   To reproduce the following results I temporarily added 3 scripts for building, testing, benchmarking as well as a jupyter notebook to visualize results. You can verify yourself by running: ./simd-build.sh && ./simd-test.sh && ./simd-bench.sh and executing the notebook as is.

   Results

2. Raimo33 renamed this:
   Add simd
   Add intel simd
   on Jul 18, 2025
3. 
   Raimo33 commented at 3:18 pm on July 18, 2025: none

   To precompute simd constants at the start, the best solution I found was doing something like this:

   0#ifdef __SSE2__
   1  static __m128i _128_vec_ones;
   2#endif
   3
   4CONSTRUCTOR void simd_init(void)
   5{
   6#ifdef __SSE2__
   7  _128_vec_ones   = _mm_set1_epi8('1');
   8#endif
   9}
   

   where CONSTRUCTOR is __attribute__((constructor))

4. 
   Raimo33 commented at 5:00 pm on July 18, 2025: none

   I’m constantly getting these warnings. Apparently they’re harmless since I always use loadu and storeu, but for some reason the compiler doesn’t like them.

   0warning: cast increases required alignment of target type [-Wcast-align]
   1  653 |         _mm256_storeu_si256((__m256i *)r->v, out);
   

   The only fixes I found are:

   1. aligning everything to 64bytes (impossible, breaks even some of my avx logic)
   2. suppress the warning globally
   3. suppress the warning inline each time
5. Raimo33 force-pushed on Aug 1, 2025
6. Raimo33 renamed this:
   Add intel simd
   [WIP] Add intel simd
   on Aug 23, 2025
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