[swiftc] Swift compiler hook does not work

The FrontendObserver has changed. I thought that we could simply call CompilerInstance.takeSILModule() when configuredCompiler(...) is called, but I then realized that the CompilerInstance does not yet contain the SILModule at that point.

I don’t think there is a way for us to get the SILModule without having to change the Frontend ourselves, which would require forking the Swift repo, and that is not ideal.

I have submitted a post on the Swift forums.

[tiganov]

They have agreed to reverse the changes. Forum post. Pull request.

Would you be willing to commit some small implementations that can go in unittest/Frontend so that we know not to remove them again in the future?

I guess they want a unit test to be written for it.

[tiganov]

there must be some reasons that the upstream write its own passes instead of using FrontendTool.

Isn’t the FrontendTool used instead of the swift/tools? Do those tools not simply exist for certain situations where you do not need to run the whole compiler?

Not only SILLLVMGen, but also other tools […]

Yes, and they combined make up quite a bit of code that needs to be maintained. Not to mention it would take time to combine all of these tools. Or to copy the driver + frontend, which basically has the same function as these tools combined. My time on the this project is limited to this summer and I would like to start writing the analysis ASAP. It might take me over a week to write a custom driver (since it would involve learning the compiler much more in depth) and that’s a lot of time for me.

https://github.com/apple/swift/commits/28bad2b4a4edb95df90bfd0e7cac0c0c7b53e869/tools/sil-llvm-gen/SILLLVMGen.cpp

You have a fair point in that these tools do not change often, and we could just copy their changes.