[WIP] Trying to Dump IR or Line Numbers of Loops

[mostafaelhoushi]

I have been trying to print line numbers of loops, or print the IR content of loops (in order to extract loop features separately) using these statements:

      L->getLoopID()->dump();
      L->dump();
      L->getLocRange().getStart().dump();
      L->getLocRange().getEnd().dump();
      L->getStartLoc().getLine();

but they all lead to this error:

dyld: lazy symbol binding failed: Symbol not found: __ZNK4llvm8Metadata4dumpEv
  Referenced from: /private/var/tmp/_bazel_melhoushi/29d44ffac89bbd569101bd339ac68a0b/execroot/CompilerGym/bazel-out/darwin-fastbuild/bin/examples/example_unrolling_service/loop_unroller/loop_unroller
  Expected in: flat namespace

dyld: Symbol not found: __ZNK4llvm8Metadata4dumpEv
  Referenced from: /private/var/tmp/_bazel_melhoushi/29d44ffac89bbd569101bd339ac68a0b/execroot/CompilerGym/bazel-out/darwin-fastbuild/bin/examples/example_unrolling_service/loop_unroller/loop_unroller
  Expected in: flat namespace

I have tried to add libLLVMRuntimeDyld as a TARGET to the build system as shown in this pull request but it didn't work. Perhaps I have added it the wrong way. Can @ChrisCummins please take a look?

[codecov-commenter]

Codecov Report

Merging #493 (84be5ce) into development (724f23c) will decrease coverage by 0.50%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           development     #493      +/-   ##
===============================================
- Coverage        87.93%   87.43%   -0.51%     
===============================================
  Files              111      113       +2     
  Lines             6182     6397     +215     
===============================================
+ Hits              5436     5593     +157     
- Misses             746      804      +58     

Impacted Files	Coverage Δ
compiler_gym/util/registration.py	80.00% <0.00%> (-20.00%)	⬇️
compiler_gym/envs/gcc/datasets/chstone.py	91.17% <0.00%> (-2.95%)	⬇️
...loop_tool/service/loop_tool_compilation_session.py	88.59% <0.00%> (-1.35%)	⬇️
compiler_gym/wrappers/datasets.py	95.91% <0.00%> (-1.06%)	⬇️
compiler_gym/service/connection.py	78.71% <0.00%> (-0.68%)	⬇️
compiler_gym/envs/compiler_env.py	89.47% <0.00%> (-0.48%)	⬇️
...er_gym/third_party/inst2vec/inst2vec_preprocess.py	73.94% <0.00%> (-0.29%)	⬇️
compiler_gym/wrappers/__init__.py	100.00% <0.00%> (ø)
compiler_gym/envs/llvm/compute_observation.py	89.58% <0.00%> (ø)
compiler_gym/util/executor.py	74.43% <0.00%> (ø)
... and 1 more

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[ChrisCummins]

Hey @mostafaelhoushi, I have seen similar errors before. I think the problem is that there is some library missing in the linker flags for LLVM I define here which causes the required .so file to not be linked into the binary:

https://github.com/ChrisCummins/bazel_llvm/blob/development/10.0.0/BUILD#L477-L672

To be honest, in the one time I encountered a similar problem, I ended up working around it rather than fixing it, because the debugging loop was so slow 😬

I might get a bit of time towards the start of next week to try and see if I can fix it. If not, is there an alternative API you can call to dump the line numbers?

Cheers,
Chris

[ChrisCummins]

@mostafaelhoushi you may find that this kind of error goes away when building with cmake (#498) rather than my janky bazel integration. It isn't yet a full replacement for the bazel build but this may be enough to unblock you.

Cheers,
Chris

[mostafaelhoushi]

@mostafaelhoushi you may find that this kind of error goes away when building with cmake (#498) rather than my janky bazel integration. It isn't yet a full replacement for the bazel build but this may be enough to unblock you.

Cheers, Chris

Perfect! I will try it with the docker. Thanks Chris!

[mostafaelhoushi]

I have good news.
I was able to get CMake working on the loop unroller in this PR: #530

And then CMake made it easier for me to debug the build error. It turned out that we need to build LLVM in debug mode or add -DLLVM_ENABLE_DUMP during the build of LLVM:
https://github.com/llvm/llvm-project/blob/53dc5258282a8322451cba14b5ad2f670028d196/llvm/lib/Analysis/LoopInfo.cpp#L669-L675

Instead of having to modify the build of LLVM, I was able to invoke ->print(llvm::dbgs(), true, true) to print the IR instructions inside the loop.

So now, we can dump the loop with both bazel and CMake!

I will clean up the code and update this PR.

[ChrisCummins]

Fantastic work @mostafaelhoushi! This is a great example of the value of being able to customize the LLVM build that CompilerGym uses. Nice!

cc @sogartar

[mostafaelhoushi]

Will close this PR as I am working on another branch to dump loop data