That is, they are compiling C with GCC, but Rust uses LLVM as a backend. Compiling their C code with clang reveals that it is also slightly slower than the C code compiled by GCC, but not faster than Rust.
The actual conclusion here is that the GCC toolchain is slightly faster than the LLVM toolchain for this particular use case, but that isn't really news - it happens all the time.
If one want to focus this on Rust, then the downside of Rust vs C here is that C has a GCC toolchain that happens to be faster for this use case, but Rust does not.
That is, they are compiling C with GCC, but Rust uses LLVM as a backend. Compiling their C code with clang reveals that it is also slightly slower than the C code compiled by GCC, but not faster than Rust.
The actual conclusion here is that the GCC toolchain is slightly faster than the LLVM toolchain for this particular use case, but that isn't really news - it happens all the time.
If one want to focus this on Rust, then the downside of Rust vs C here is that C has a GCC toolchain that happens to be faster for this use case, but Rust does not.