rustc is a cross-compiler by default. This means that you can use any compiler to build for any architecture. The list of targets are the possible architectures that you can build for.

To see all the options that you can set with a target, see the docs here.

To compile to a particular target, use the --target flag:

$ rustc src/ --target=wasm32-unknown-unknown

Target Features

x86, and ARMv8 are two popular CPU architectures. Their instruction sets form a common baseline across most CPUs. However, some CPUs extend these with custom instruction sets, e.g. vector (AVX), bitwise manipulation (BMI) or cryptographic (AES).

Developers, who know on which CPUs their compiled code is going to run can choose to add (or remove) CPU specific instruction sets via the -C target-feature=val flag.

Please note, that this flag is generally considered as unsafe. More details can be found in this section.