onnx-runtime-ep-cpu

The CPU execution provider for the ORT 2.0 runtime (see docs/ORT2.md §4.4 and §54 Phase 1). It implements [onnx_runtime_ep_api::ExecutionProvider] and hosts pure-Rust reference kernels for the Phase-1 op set (MatMul, Add, Relu, Reshape, Transpose, Gather, LayerNormalization).

Backends: correctness baseline + optional oneDNN

The GEMM hot spot is served through [backend::CpuBackend] (docs/ORT2.md §25.2). The default backend is a pure-Rust blocked, register-tiled, rayon-parallelized f32 GEMM — the portable, offline correctness baseline that compiles anywhere with no C++/FFI. The non-default onednn cargo feature statically links oneDNN and routes the 2-D tile GEMM through dnnl_sgemm ([kernels::onednn]). Every backend lives behind the [onnx_runtime_ep_api::Kernel] trait, so neither the EP contract nor the session observes which one ran. See [kernels::matmul] for the hot spot.

unsafe

The default (Generic) path is unsafe-minimal: the only unsafe is the raw device-buffer access the ep-api contract forces (aligned host alloc/dealloc, memcpy, and strided element reads/writes), each isolated and SAFETY-documented, plus — only under the onednn feature — the dnnl_sgemm FFI call, confined to [kernels::onednn]. The blocked rayon GEMM itself contains no unsafe; all kernel arithmetic is safe Rust operating on dense Vec<f32> buffers produced by the two audited accessors in [kernels].