Enhance Loop Unroller

[mostafaelhoushi]

We have noticed that the unrolling factor passed to opt as --unroll-count=<num> cli option doesn't always take effect.
This PR provides a custom LLVM loop unroller that enforces the unroll count factor provided in an action..

To run custom unroller:

bazel run //examples/example_unrolling_service/loop_unroller:loop_unroller -- <input>.ll -o <output>.ll  --funroll-count=<num>

To run end-to-end example:

bazel run //examples/example_unrolling_service:example

[codecov-commenter]

Codecov Report

Merging #477 (724f23c) into development (94c9e79) will increase coverage by 0.17%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           development     #477      +/-   ##
===============================================
+ Coverage        87.75%   87.93%   +0.17%     
===============================================
  Files              111      111              
  Lines             6181     6182       +1     
===============================================
+ Hits              5424     5436      +12     
+ Misses             757      746      -11     

Impacted Files	Coverage Δ
compiler_gym/envs/llvm/compute_observation.py	89.58% <0.00%> (+0.22%)	⬆️
compiler_gym/envs/compiler_env.py	89.95% <0.00%> (+0.47%)	⬆️
...loop_tool/service/loop_tool_compilation_session.py	89.93% <0.00%> (+1.34%)	⬆️
compiler_gym/service/connection.py	79.39% <0.00%> (+2.36%)	⬆️

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[mostafaelhoushi]

Update: Thanks for @hughleat for his help. Counting the loops is now solved. Next step is to update the loop metadata

[ChrisCummins]

I had a pick through the code and it all looks good to me (minor comments inline). I'm guessing with this being WIP that the glue code to interface with an environment is coming later. Just ping me whenever you want me to take a look through :-)

Cheers,
Chris

[mostafaelhoushi]

I had a pick through the code and it all looks good to me (minor comments inline). I'm guessing with this being WIP that the glue code to interface with an environment is coming later. Just ping me whenever you want me to take a look through :-)

Cheers, Chris

Thanks Chris. I have addressed all the comments.
Yes, now I have updated the environment to call the custom unroller. I have also made it optional in case someone wants to use LLVM's default unroller

[mostafaelhoushi]

Just ping me whenever you want me to take a look through :-)

I merged it without pinging you :(
Do you want to take another look and make changes?

[ChrisCummins]

I merged it without pinging you :( Do you want to take another look and make changes?

No worries! Code looks great :) I'll try it out and let you know if i encounter any problems

Cheers,
Chris