[llvm-dev] Organization of LLVM utilities

[Fangrui Song via llvm-dev]

On 2020-08-04, Chris Lattner via llvm-dev wrote:
>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

llvm/test/CMakeLists.txt LLVM_TEST_DEPENDS lists many utilities. If I
understand correctly, every test under llvm/test/ requires to build all
tools listed in LLVM_TEST_DEPENDS. This is probably fine because these
utilities are all small.

>
>> 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
>>
>>
>> ----------------------------------------------------------------
>> Windfall               Paul C. Anagnostopoulos
>>      ----------------------------------------------------------
>>   Software            978 369-0839
>>                             www.windfall.com
>> ----------------------------------------------------------------
>> My life has been filled with calamities,
>> some of which actually happened.
>> ---Mark Twain
>>
>> Guga 'mzimba, sala 'nhliziyo
>>
>
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