[LLVMdev] Proposal: split tools/opt/opt.cpp to OptTool and a smaller main()

[Sean Silva]

I thought that opt was supposed to basically be a way to run a PassManager
over some IR? Seems like the new PM should standardize the appropriate
things and have them be a natural part of its API.

-- Sean Silva


On Tue, Feb 11, 2014 at 1:42 PM, Eli Bendersky <eliben at google.com> wrote:

> Hello,
>
> I started some refactoring work on tools/opt/opt.cpp in r201116, but
> conceptually this is part of a larger effort. I'd like to consult with
> llvmdev@ about the best way to move this forward.
>
> Background: opt is a very useful swiss-army-knife tool, and its
> capabilities may be useful to custom tools. However, as it stands now opt
> is now very modular - almost all its functionality is contained within its
> main opt.cpp file.
>
> I think this is also the cause of some code duplication that currently
> exists between different LLVM tools. For example, some code from opt.cpp is
> duplicated in llc.cpp; the same is true for the logic of adding
> optimization passes between opt.cpp and Clang (a comment in opt.cpp even
> admits it "duplicates llvm-gcc behaviour", showing its age :-) A lot of
> cl::opt definitions are duplicated between different tools and have to be
> kept in sync for consistency.
>
> What I'd like to see is most of opt's functionality moving outside of
> opt.cpp to make it reusable in other tools. For example, this could be
> encapsulated in a class named OptTool, or just a namespace with a bunch of
> utility functions, as well as cl::opt definitions.
>
> Such a transition can be done in steps: the first step would be to create
> this OptTool within tools/opt. This would immediately enable building
> custom opt-based tools by linking in the code from tools/opt, leaving
> tools/opt/opt.cpp out. A more ambitious step would be to move the
> functionality to a library (lib/Tools?) - enabling code reuse between
> different LLVM tools as well as easier use within custom tools.
>
> Any opinions / suggestions welcome. I'll be happy to send out piecemeal
> patches that implement this refactoring.
>
> Eli
>
>
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