Wire up basic functions and features for SSE2 support using the SSE4.1 version
as a basis without implementing the SSE2 instructions yet.
* Cargo.toml: add no_sse2 feature
* benches/bench.rs: wire SSE2 benchmarks
* build.rs: add SSE2 rust intrinsics and assembly builds
* c/Makefile.testing: add SSE2 C and assembly targets
* c/README.md: add SSE2 to C build instructions
* c/blake3_c_rust_bindings/build.rs: add SSE2 C rust binding builds
* c/blake3_c_rust_bindings/src/lib.rs: add SSE2 C rust bindings
* c/blake3_dispatch.c: add SSE2 C dispatch
* c/blake3_impl.h: add SSE2 C function prototypes
* c/blake3_sse2.c: add SSE2 C intrinsic file starting with SSE4.1 version
* c/blake3_sse2_x86-64_{unix.S,windows_gnu.S,windows_msvc.asm}: add SSE2
assembly files starting with SSE4.1 version
* src/ffi_sse2.rs: add rust implementation using SSE2 C rust bindings
* src/lib.rs: add SSE2 rust intrinsics and SSE2 C rust binding rust SSE2 module
configurations
* src/platform.rs: add SSE2 rust platform detection and dispatch
* src/rust_sse2.rs: add SSE2 rust intrinsic file starting with SSE4.1 version
* tools/instruction_set_support/src/main.rs: add SSE2 feature detection
This gives the assembly files the same prefix as the intrinsics files which
simplifies building when the build system should pick between the assembly and
the intrinsics files.
Currently this requires setting the BLAKE3_USE_NEON preprocessor flag.
In the future we may enable this automatically on AArch32/64 or include
some kind of dynamic feature detection. (Though ARM makes this harder
than x86.)
As part of this, get rid of the IS_ARM flag. It wasn't being set
properly when I tried it on a Raspberry Pi.
Closes #30.