[llvm-dev] Incrementally compiling LLVM

[David Blaikie via llvm-dev]

On Thu, Apr 15, 2021 at 9:22 AM Francesco Bertolaccini
<francesco at bertolaccini.dev> wrote:
>
> On 15/04/2021 03:36, Stephen Neuendorffer wrote:
> > This flow is being used successfully by both npcomp and circt, which are
> > llvm incubator projects.  You should be able to leverage/build off of
> > the github actions flows that they define.
> > see https://github.com/llvm/circt <https://github.com/llvm/circt>
> > and https://github.com/llvm/mlir-npcomp
> > <https://github.com/llvm/mlir-npcomp>
> >
> > Steve
> >
> I have not yet tried the ccache solution mentioned before, but I tried
> changing my flow to use the Visual Studio generator instead of Ninja,
> like the linked projects do, and it still takes a long while to do a
> recompilation, even though I just re-run the job
> (https://github.com/frabert/llvm-project/runs/2354303561)

Yeah, I don't know how github actions work at all, or what might be
causing them to rebuild everything... maybe they copy the files into a
new location every time they run the actions, which updates the last
modified time and causes everything to rebuild? No idea.

> I am now wondering: does the fact that I am *not* enabling the host
> target affect something? I am only interested in the Mips target so it's
> the only one I enable, thinking it was going to speed up compilation,
> but maybe I am not doing myself any favors?

No, I shouldn't think that would adversely effect the ability to rebuild things.