Dispatch outside the inner loop.

Select a known backend at build time

Flyology_SIMD.Algorithms.Generic_Bytes is the compile-time composition contract for representative byte algorithms. The repository instantiates it as Algorithms.Scalar and Algorithms.Native.

Result :=
  Flyology_SIMD.Algorithms.Native.Find_First (Data, Needle);

The selected native backend is AArch64 NEON, x86-64 SSE2, or scalar according to the GPR scenario. The generic receives primitive operations as formal subprograms so GNAT can inline through the complete loop.

Select once for a complete buffer

Flyology_SIMD.Algorithms.Runtime accepts an optional backend for Find_First, Count, and Is_ASCII. The default is the best safe backend available to the process.

Matches :=
  Flyology_SIMD.Algorithms.Runtime.Count
    (Data    => Data,
     Needle  => Flyology_SIMD.U8 (16#2C#),
     Backend => Flyology_SIMD.Features.Best_Available);

The runtime package performs one case selection for the array operation. It does not probe features or call an indirect target for every vector primitive.

Inspect and require availability

Flyology_SIMD.Features distinguishes a backend that was compiled from one that can execute safely on the current processor and operating system. Available performs the complete availability test. Require raises Backend_Unavailable instead of entering unsupported code.

Best_Available returns NEON on AArch64, AVX2 when the complete x86 gate succeeds, SSE2 on the x86-64 baseline, or scalar elsewhere.

Keep optional instructions out of baseline objects

On x86-64, AVX2 detection checks CPU feature bits and operating-system extended-state support. The AVX2 implementation is a separate object configuration. Linking it does not execute an AVX2 instruction during elaboration.

The feature detector, scalar backend, and SSE2 backend compile with AVX disabled. Focused code-generation checks reject AVX instructions outside the optional object and reject primitive calls inside the representative vector loop.