Support multi-threaded compilation for --build

Search Terms

Project references, multi-thread, compilation, performance

Suggestion

We have migrated our main project to use project references. It simplifies the development workflow, but brings basically 0 noticeable performance improvement (for both local development and CI). There's even an illusion that now we get worse performance during development.

I guess the main reason behind this is lacking support for multi-thread compilation.

Use Cases

Improve compilation performance.

Examples

N/A

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

The issue names the --build workflow but does not identify files, tests, or an implementation entry point. Start by locating the --build compilation path and reviewing how project references are compiled. Done means multi-threaded compilation improves performance without changing emitted JavaScript or existing runtime behavior.