llvm dev - Jul 2019 - Looking for an out-of-source "Hello, world" LLVM/Clang pass example

Andrzej,

On 7/14/19 8:02 AM, Andrzej Warzynski wrote:
> This is still very early stages, but you can be my guinea pig:
>
> https://github.com/banach-space/llvm-tutor
>
> It's a tutorial that I've been preparing recently and am hoping to
> present somewhere at some point :-) I believe that it already covers 1),
> 2) and 3). I haven't had the time to work on 4). It's based on
LLVM-8
> and includes a working CI set-up, so that you can be confident that it
> works. If it doesn't, ping me - I'm keen on improving it.
Cool, thanks.  I just started reading over that now.  I have a couple
of questions already, if you don't mind:

1) I see you're building the pass with

    add_library(lt-cc-static STATIC StaticCallCounter.cpp
DynamicCallCounter.cpp)
    add_library(lt-cc-shared MODULE StaticCallCounter.cpp
DynamicCallCounter.cpp)

  What's the reason for building a STATIC version?  Does any LLVM tool
  make use of that?

  Is add_library the preferred pass-building CMake macro these days,
  as opposed to add_llvm_library or add_llvm_loadable_module?

2) How is the user supposed to install the generated files?  Neither
   "make install" nor "cmake --target=install" seem to work.

-- Scott

This review https://reviews.llvm.org/D61446 tries hard to address your
needs: it makes it possible to register a pass withing clang/opt/bugpoint
with a dedicated cmake function call. The pass can then behave as a
loadable plugin or be linked statically to LLVM (depending on cmake
options), and the code can live out-of-tree, much like polly.

On Tue, Jul 16, 2019 at 12:01 AM Scott Pakin via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Andrzej,
>
> On 7/14/19 8:02 AM, Andrzej Warzynski wrote:
> > This is still very early stages, but you can be my guinea pig:
> >
> > https://github.com/banach-space/llvm-tutor
> >
> > It's a tutorial that I've been preparing recently and am
hoping to
> > present somewhere at some point :-) I believe that it already covers
1),
> > 2) and 3). I haven't had the time to work on 4). It's based on
LLVM-8
> > and includes a working CI set-up, so that you can be confident that it
> > works. If it doesn't, ping me - I'm keen on improving it.
>
> Cool, thanks.  I just started reading over that now.  I have a couple
> of questions already, if you don't mind:
>
> 1) I see you're building the pass with
>
>     add_library(lt-cc-static STATIC StaticCallCounter.cpp
> DynamicCallCounter.cpp)
>     add_library(lt-cc-shared MODULE StaticCallCounter.cpp
> DynamicCallCounter.cpp)
>
>   What's the reason for building a STATIC version?  Does any LLVM tool
>   make use of that?
>
>   Is add_library the preferred pass-building CMake macro these days,
>   as opposed to add_llvm_library or add_llvm_loadable_module?
>
> 2) How is the user supposed to install the generated files?  Neither
>    "make install" nor "cmake --target=install" seem to
work.
>
> -- Scott
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Hi Scott,

This is useful feedback for me, thanks! As you've noticed, that project
is Work In Progress, which has been on hold for a while. I'm about to
get back to it, and you've already given me some good hints as what to
improve.

My replies inline.

On 15/07/2019 23:01, Scott Pakin wrote:
> Andrzej,
>
> On 7/14/19 8:02 AM, Andrzej Warzynski wrote:
>> This is still very early stages, but you can be my guinea pig:
>>
>> https://github.com/banach-space/llvm-tutor
>>
>> It's a tutorial that I've been preparing recently and am hoping
to
>> present somewhere at some point :-) I believe that it already covers
1),
>> 2) and 3). I haven't had the time to work on 4). It's based on
LLVM-8
>> and includes a working CI set-up, so that you can be confident that it
>> works. If it doesn't, ping me - I'm keen on improving it.
>
> Cool, thanks.  I just started reading over that now.  I have a couple
> of questions already, if you don't mind:
>
> 1) I see you're building the pass with
>
>      add_library(lt-cc-static STATIC StaticCallCounter.cpp
> DynamicCallCounter.cpp)
>      add_library(lt-cc-shared MODULE StaticCallCounter.cpp
> DynamicCallCounter.cpp)
>
>    What's the reason for building a STATIC version?  Does any LLVM tool
>    make use of that?
Good catch - I honestly don't remember. Let me check that and I'll get
back to you.
>
>    Is add_library the preferred pass-building CMake macro these days,
>    as opposed to add_llvm_library or add_llvm_loadable_module?
My motivation was to make it as standalone and basic as possible.
add_library was sufficient and that's what I used.
>
> 2) How is the user supposed to install the generated files?  Neither
>     "make install" nor "cmake --target=install" seem to
work.
I have not considered that at all. Added to my TODO list.
>
> -- Scott
>
-- Andrzej
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On 7/17/19 7:17 AM, Serge Guelton wrote:
> This review https://reviews.llvm.org/D61446 tries hard to address your
> needs: it makes it possible to register a pass withing
> clang/opt/bugpoint with a dedicated cmake function call. The pass can
> then behave as a loadable plugin or be linked statically to LLVM
> (depending on cmake options), and the code can live out-of-tree, much
> like polly.
Thanks.  I had looked at Polly in the past.  I guess I should take
another look now that I more clearly know what I'm looking for.

-- Scott