How to add an operation to spec

Read doc.go for overall guidance.

Any operation we may add is already defined in the simd or simd/archsimd packages. Use those as reference. Check their existing documentation using, for example GOEXPERIMENT=simd go doc simd ReduceSum or GOEXPERIMENT=simd GOARCH=amd64 go doc archsimd MulAdd. For each operation, check the archsimd docs for GOARCH amd64, arm64, and wasm.

If you are writing the function declaration, note that spec is maximalist, so consider how an operation can be generalized past types that may appear in simd or archsimd. For example, numerical operations on just ints can often be generalized to ints or uints. Often, numerical operations on floats can be generalized to ints or uints, though be wary of introducing new complicated overflow or rounding behavior in this case.

For the function implementation, look to simd/simd_emulated.go and simd/archsimd/internal/simd_test for inspiration. simd_emulated.go operates entirely on concrete types, while spec operates on generic types. Typically it’s easy to generalize across float types or int/uint types, though it may not be easy to generalize one implementation for both float and int/uint. In that case, it’s okay to split it into two implementations (for an example, see AbsFloat and AbsInt).

You can write temporary tests to check your work, but don’t keep them. We do not test every operation in spec because it will ultimately be checked against the hardware.

Tell the user about any corner-case behavior, how you resolved it, and whether or not it was consistent across simd and archsimd across platforms.