Code size optimizations

[kateinoigakukun]

Motivation

Code size is a critical part of reducing initial (un-cached) startup time as it affects download size and compilation time inside Wasm engine.

Sub-tasks

• Unlock LTO #5601
• Explore if we can use archive link instead of object link in SwiftPM
• Provide a way to strip a part of ICU data embedded through http://github.com/swiftlang/swift-foundation-icu
  • See https://github.com/GoodNotes/swift-icudata-slim

[andreaTP]

Hi @kateinoigakukun and thanks for the great work!

I'd like to provide some additional data points, from this brief exploration:

• an hello world program currently compiles to a ~6.8M wasm file
• using wasm-opt on the resulting binary strip it down to half the size 3.3-3.4Mb