cpu: de-duplicate some of the operators and refactor

[cmdr2]

Note: This PR only deletes lines from ggml-cpu.c, it does not modify any functions in it. I'm not sure why git diff tries to combine them as changes. Standard diff shows the correct diff of ggml-cpu.c: https://gist.github.com/cmdr2/a76df5af311417619788e8330b1908b3

This PR de-duplicates some of the easily-templatized functions in ggml-cpu.c. It takes inspiration from binbcast.cu and common.cuh.

• Binary: add, sub, mul, div
• Unary: abs, sgn, neg, step, tanh, elu, relu, sigmoid, hardsigmoid, exp, hardswish, sqr, sqrt, sin, cos, log

This removes the op implementation functions from ggml-cpu.c (around 2000 lines). As a side-effect, all the functions now support bf16 as well as non-contiguous src1.

The performance is the same as the current implementation. It also passes all the runners on ggml-ci, which tested non-contiguous inputs (in SAM) and vDSP on Mac.

[ggerganov]

Hopefully all C++ compilers support structured bindings today. If we encounter issues, we might have to return simple struct of integers.

[ggerganov]

Wait for @slaren's review before merging. Thanks!

[cmdr2]

Wait for slaren's review before merging. Thanks!

@ggerganov Yes, will do :)

Thanks for the comments, fixed them in the latest commit. The CI runner also passes.

[slaren]

I will review when I have a chance, but I may not be able to do it for a few days.

[cmdr2]

Thanks @slaren No hurry :)

@slaren @ggerganov I made some progress on the next PR (a bigger refactor). It's working after the refactor, and passes the runners on ggml-ci. ggml-cpu.c is at about 3500 lines after this refactoring (down from ~15,000 lines).

Just thought of sharing the approach early, to see if you see any obvious red-flags.

I'll split it into two PRs:

1. Move the SIMD Mapping lines into a separate header file, and the ggml_vec_ function lines into a separate header file. The vec file imports the SIMD mappings file. No other changes.
2. Move all the operator function lines (except mul_mat) into a separate C++ file. This file imports the vec functions header.

The operator functions file needed a very small number of cosmetic changes, like replacing direct references to type_traits_cpu with ggml_get_type_traits_cpu(), using static_cast<ggml_op_pool>(opts[0]) etc.

At a broad level, does this approach raise any obvious red-flags for you? It seems to work on all the ggml-ci runners, and doesn't seem to skip any CPU extension. But I'll test and read the diff a few more times before submitting the PRs.

Thanks