Running build-toolchain incrementally

Development Compiler
1

Hi folks, I've been using ./utils/build-toolchain local.swift to build a local toolchain, but subsequent builds are quite long, perhaps not leveraging the same incremental build benefits as other methods of building Swift artifacts, like build-script directly.

For example, running the same build command twice (./utils/build-toolchain local.swift), I'd expect the second run to be pretty fast since there have been no changes, when in reality it takes closer to 30 minutes on my 2.9 GHz Intel Core i9 2018 MBP.

Is there a flag I'm missing to opt in to incremental toolchain builds?

2

I've observed the same non-fully-incremental behavior of build-toolchain - with no code changes, a second invocation always seems to rebuild the standard library.

3

I saw similar behaviour in the past when working on build-script. If someone is setup to reproduce this, modifying build script to invoke ninja with extra options ninja -d explain -v may tell us what is going on.