[llvm-dev] Organization of LLVM utilities

[Chris Lattner via llvm-dev]

It may be confusing but it is not the case that “llvm/lib” contains all the libraries, and “llvm/tools” contains all the tools.  At a course grain, the main llvm repo builds in four phases:

1) llvm/utils.  -> this builds some executables like tablegen
2) llvm/lib.     -> This is all libraries, shouldn’t include executables.
3) llvm/tools. -> Generally executables, also some libraries that are tool specific.
4) tests..        -> Things that depend on the above.

In theory, we could have a much finer grain build system that allows tracking exactly which tests depend on which executables, which executables depend on which libraries, etc, but this hasn’t been done.  In theory this could help the build cycle if you’re running a single “llvm-mc” like test, for example.

-Chris


> On Aug 4, 2020, at 12:06 PM, Paul C. Anagnostopoulos <paul at windfall.com> wrote:
> 
> Could you expand on this a bit? I see from my build directory that llvm-tblgen.exe was built before the Target/* .inc files. It sounds like you're saying that something has to be built between the .exe and the .inc files.
> 
> At 8/4/2020 02:44 PM, Chris Lattner wrote:
> 
> 
>>> On Aug 4, 2020, at 11:31 AM, Paul C. Anagnostopoulos via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>> 
>>> I was confused by the lack of TableGen backends in the llvm/lib/tablegen directory until I stumbled upon the llvm/utils/tablegen directory. Could someone explain why TableGen is divided into these two directories?
>> 
>> The mechanical reason is that llvm/utils builds before llvm/libs.  The basic TableGen support is required to generate .inc files in the libs directory.
>> 
>> -Chris
> 
> 
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