9562b69b4f
The upcoming SIMD support in the wasm target is unique from the other platforms where it's either unconditionally available or not available, there's no halfway where a subsection of the program can use it but no other parts of the program can use it. In this world it's valid for wasm SIMD args to always be passed by value and there's no need to pass them by reference. This commit adds a new custom target specification option `simd_types_indirect` which defaults to `true`, but the wasm backend disables this and sets it to `false`.
librustc_target contains some very low-level details that are
specific to different compilation targets and so forth.
For more information about how rustc works, see the rustc guide.