Contributing support for a Wasm instruction to Winch

Contributing support for a Wasm instruction to Winch

摘要

A month ago I landed a pull request to Winch, Wasmtime's baseline (non-optimizing) compiler, to add support for a number of WebAssembly instructions. Shopify is working on Winch to make Wasm compilation faster. I learned a number of important parts of the codebase and how to test the changes I made which I'll outline below.

Adding support for a WebAssembly instruction means that when Winch encounters a given instruction, it emits zero or more native machine code instructions to perform the operation while ensuring the WebAssembly stack is in the correct state and that CPU registers are appropriately allocated or freed.