There's some confusion I'll try to clear up here. I don't want to use Tablegen. 
It was just something Sean said about TableGenBackends.h where I thought he was 
suggesting I use TableGen. After looking into the header I'm pretty sure he 
didn't actually mean that.

I really do want a simple design with subclasses of Transform implementing 
specific transformations and those subclasses being instantiated by main based 
on what args are on the command-line. However, to satisfy the design 
requirement of making transforms easy to add and not having to change any 
central code every time a transform is added, I wanted to use something like 
LLVM's Pass mechanism for registration so the the pairing between command-line 
arg and class to instantiate is contained within transform code. This way a 
developer only has to add code to the tool and not have to change anything in 
the existing code when adding a new transform.

The registration mechanism as it exists on phabricator now works for this 
purpose except that all sources need to be linked into the tool directly and 
not via static libs or else the global registration variables don't get 
included. I have a solution in cmake which is very straightforward but the 
legacy Makefile system is giving me issues. I'm debugging it now.

From: Manuel Klimek [mailto:[email protected]]
Sent: Thursday, December 20, 2012 11:06 AM
To: Vane, Edwin
Cc: [email protected]; 
[email protected]
Subject: Re: [cfe-commits] [PATCH] Foundation for Transform registration 
infrastructure

On Thu, Dec 20, 2012 at 3:39 PM, Vane, Edwin 
<[email protected]<mailto:[email protected]>> wrote:
I wasn't planning on dynamically loading transforms. Yesterday when I tried 
turning a transform into a static library to link into cpp11-migrate I was 
reminded that unused global variables like the RegisterTransform<...> vars 
won't get included in the link. My next goal is just to set up the build system 
to slurp through subdirectories adding all sources to the executable as one 
monolithic entity. I'm not sure how this is any less complex than using 
tablegen although I admit I don't have much experience with it.

Why tablegen? I'm still not sure why we need anything but simple classes that 
can be instantiated...
Can you give examples of what you want to do that this wouldn't fulfill?

Thanks,
/Manuel


-----Original Message-----
From: Manuel Klimek [mailto:[email protected]<mailto:[email protected]>]
Sent: Thursday, December 20, 2012 2:43 AM
To: [email protected]<mailto:[email protected]>; Vane, Edwin
Cc: [email protected]<mailto:[email protected]>; 
[email protected]<mailto:[email protected]>; 
[email protected]<mailto:[email protected]>
Subject: Re: [PATCH] Foundation for Transform registration infrastructure

  Sean's main point is my primary question: why do we need to load stuff 
dynamically?

  I would expect to have a Transform class at some point, and have main 
basically look like:
  if (Flag1)
    Transforms.push_back(new T1);
  ...
  and then do something with the vector of transforms we've built - that 
wouldn't need any plugin infrastructure.

  PS: regarding my rants - many people in llvm disagree with my positions here 
:) There's a lot of taste and personal preference to them, so if you agree with 
my reasoning, cool, but always feel free to argue if you don't agree :) I'm 
happy to learn new points of view

http://llvm-reviews.chandlerc.com/D221
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