Comment by wyldfire

16 days ago

Does Rust provide architecture-specific intrinsics like C/C++ toolchains usually do? That's a popular way to do SIMD.

4 comments

wyldfire

Reply
steveklabnik  16 days ago

Yes https://doc.rust-lang.org/stable/std/arch/

  • m-hilgendorf  16 days ago

    People should be aware though that without `-C target_feature=+<feature>` in your rustc flags the compiler may emit function calls to stubs for the intrinsic. So people should make sure they're passing the appropriate target features, especially when benchmarking.

    [0] https://godbolt.org/z/85nx44zcE

    edited: I tested gcc/clang and they just straight up fail to compile without -msse3. The generated code without optimizations is also pretty bonkers!

    • wyldfire  16 days ago

      > compiler may emit function calls to stubs for the intrinsic.

      I guess the compiler itself might not know how those calls get resolved but the linker or cargo or some other mechanism might decide to include a library that provides stubs.

      Why would anyone ever want that behavior? nop stubs could conceivably be used in some compiler isolated (no-execution) testing scenario but I'd expect it to be opt-in.