llvm dev - Oct 2019 - RFC: Adding IR Transformation examples/tutorial code to llvm-project

On Fri, Oct 25, 2019 at 2:43 PM Michael Kruse via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> I like the idea and already discussed it with Kit Barton.
>
> Two concerns that I had:
>
> 1. Keeping them in-tree requires them to be up-to-date, a potential
> additional maintenance burden. This might be what we want, but I get
> less enthusiastic when thinking about maintaining all tutorials ever
> given at any conference during the last xx years without having gone
> through a review process.
>
As with any code in the codebase, yeah, pre or post commit review seems
good & if they end up bitrotting/becoming less relevant/diverge
significantly from the tutorial content (written, video, whatever there is)
I think it's fine to delete them. Same as we'd do with tests. (I think
they're sort of like tests, really)

>
> 2.Chris Bieneman seeks to simplify the cmake build system, including
> significantly reducing the number of configuration parameters and
> making "make all" really make everything, including examples.
This
> would make the overall configure process slower even when not
> interested in the tutorials.
>
> Michael
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Thanks for taking a look! Eric and David beat me to responding. Below are a few
additional thoughts in a similar direction.
> On 25 Oct 2019, at 14:48, David Blaikie <dblaikie at gmail.com>
wrote:
> 
> 
> 
> On Fri, Oct 25, 2019 at 2:43 PM Michael Kruse via llvm-dev <llvm-dev at
lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> I like the idea and already discussed it with Kit Barton.
> 
> Two concerns that I had:
> 
> 1. Keeping them in-tree requires them to be up-to-date, a potential
> additional maintenance burden. This might be what we want, but I get
> less enthusiastic when thinking about maintaining all tutorials ever
> given at any conference during the last xx years without having gone
> through a review process.
> 
> As with any code in the codebase, yeah, pre or post commit review seems
good & if they end up bitrotting/becoming less relevant/diverge
significantly from the tutorial content (written, video, whatever there is) I
think it's fine to delete them. Same as we'd do with tests. (I think
they're sort of like tests, really)
I think that would be great policy. 

IMO, the examples should go through reviews as well and for any changes that
break the examples, I think it is reasonable to expect the author to fix them,
similar to breaking other parts of LLVM.

But  it might be unreasonable to expect people to also update accompanying
material (e.g. a write up), except for trivial API changes. As David suggested,
if they diverge too much, we can remove them (or try to find someone who is
interested in updating them).
>  
> 
> 2.Chris Bieneman seeks to simplify the cmake build system, including
> significantly reducing the number of configuration parameters and
> making "make all" really make everything, including examples.
This
> would make the overall configure process slower even when not
> interested in the tutorials.
The suggested approach does not introduce any new options/variables, it just
adds an additional definition, if the existing LLVM_BUILD_EXAMPLES=On. So this
should not interfere with reducing the overall options. Whatever solution will
be applied to all examples should also work for the IR pass examples.

Cheers,
Florian

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Am Fr., 25. Okt. 2019 um 17:32 Uhr schrieb Florian Hahn
<florian_hahn at apple.com>:
>> 2.Chris Bieneman seeks to simplify the cmake build system, including
>> significantly reducing the number of configuration parameters and
>> making "make all" really make everything, including examples.
This
>> would make the overall configure process slower even when not
>> interested in the tutorials.
>
>
> The suggested approach does not introduce any new options/variables, it
just adds an additional definition, if the existing LLVM_BUILD_EXAMPLES=On. So
this should not interfere with reducing the overall options. Whatever solution
will be applied to all examples should also work for the IR pass examples.
I think he would like to remove LLVM_BUILD_EXAMPLES altogether. That
is, any "cmake" will execute any CMakeLists.txt, "make all"
will
always build TutorialSimplyCFG and any execution of `opt` will call
initializeExampleIRTransforms.

I am in favor of adding (more) tutorials to the repository, joint
trying to point out items to consider.

Michael