[CMake/Bazel] Support usage of opt driver as a library

[wsmoses]

In Bazel, Clang current separates the clang executable into a clang-driver library, and the actual clang executable. This allows downstream users to make their own variations of clang, without having to redo/maintain separate build pipelines.

This adds the same for opt for both CMake and Bazel.

[efriedma-quic]

If we're going to make opt-driver a library, it should be a library for both CMake and Bazel builds. The set of available libraries shouldn't depend on how you build LLVM.

[wsmoses]

I'm fine with that but FYI I emulated the clang approach, which does have this in Bazel (

llvm-project/utils/bazel/llvm-project-overlay/clang/BUILD.bazel

Line 2275 in 03a61d3

cc_library(

) but not CMake (

llvm-project/clang/tools/driver/CMakeLists.txt

Line 26 in 03a61d3

add_clang_tool(clang

)

[wsmoses]

@efriedma-quic added a CMake Library for opt. I presume we should add one for clang as well, but that should probably be a separate PR.

[efriedma-quic]

Looks okay to me, but I'm a bit worried there's something I'm missing, so I'd like a second reviewer to chime in.

[MaskRay]

This allows downstream users to make their own variations of clang, without having to redo/maintain separate build pipelines.

Consider naming the project, so if other people do any change, they can find the project name from the commit message...

It may be worth testing the following configurations:

default
-DBUILD_SHARED_LIBS=on
-DLLVM_LINK_LLVM_DYLIB=on

[wsmoses]

@efriedma-quic @MaskRay when I did the build matrix of options unfortunately the DBUILD_SHARED_LIBS one kept running into issues, so I refactored the opt library in the way shown for all of CI to succeed.

@efriedma-quic note, since I had to make a separate driver function, I made it future compatible for #79227. Once this lands, I will rebase the new test/driver in that PR on this.

[nico]

The usual llvlm style is to have one target per directory. If this is now a lib, could you move this into llvm/tools/opt/lib? Then you don't need the PARTIAL_SOURCES_INTENDED below.

[nico]

Also, this doesn't build, see e.g. here: https://lab.llvm.org/buildbot/#/builders/217/builds/35051

[nico]

Reverted in be08be5 for now.

[wsmoses]

Hm are we sure this PR contributed that failure. The link you sent seems to be in MachineScehduler.cpp

…

On Wed, Jan 24, 2024 at 1:52 PM Nico Weber ***@***.***> wrote: Reverted in be08be5 <be08be5> for now. — Reply to this email directly, view it on GitHub <#79205 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAJTUXDQVCL7C3MCE6FATUTYQFJ7NAVCNFSM6AAAAABCHTUNUWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSMBYG4ZTCMRWHA> . You are receiving this because you modified the open/close state.Message ID: ***@***.***>

[nico]

Whoops, sorry, the build failure was due to something else! I'll reland, apologies. Please do move the lib to its own dir though.

[nico]

Relanded in 3135984. Apologies again.

[wsmoses]

Will do!