b691770faa
This change adds SourceLoc information per instruction in a `VCode<Inst>` container, and keeps this information up-to-date across register allocation and branch reordering. The information is initially collected during instruction lowering, eventually collected on the MachSection, and finally provided to the environment that wraps the codegen crate for wasmtime.
This is the wasmtime-environ crate, which contains the implementations
of the ModuleEnvironment and FuncEnvironment traits from
cranelift-wasm. They effectively
implement an ABI for basic wasm compilation that defines how linear memories
are allocated, how indirect calls work, and other details. They can be used
for JITing, native object files, or other purposes.