[llvm] Adding missing global initializers when splitting a benchmark

[ChrisCummins]

• Modify split_benchmark_by_function() so that it returns an extra "benchmark", which is a single module containing no executable instructions, but all global variable definitions. This is needed to make the result of merging the split benchmarks compilable.
• Fig a buf in split_benchmark_by_function() whereby the definitions for functions marked with available_externally linkage were dropped.
• Identify two passes, -strip and -strip-nondebug, which are unsafe to run before split+merge.
• Add end-to-end tests that benchmark semantics are unchanged by splitting and merging.

Follow up to #772.

[codecov-commenter]

Codecov Report

Merging #775 (1faec6b) into development (768e4b7) will decrease coverage by 40.30%. The diff coverage is 0.00%.

Additional details and impacted files

[](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch) ```diff @@ Coverage Diff @@ ## development #775 +/- ## ================================================ - Coverage 89.01% 48.71% -40.31% ================================================ Files 131 131 Lines 8065 8074 +9 ================================================ - Hits 7179 3933 -3246 - Misses 886 4141 +3255 ``` | [Impacted Files](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch) | Coverage Δ | | |---|---|---| | [compiler\_gym/envs/llvm/llvm\_benchmark.py](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch#diff-Y29tcGlsZXJfZ3ltL2VudnMvbGx2bS9sbHZtX2JlbmNobWFyay5weQ==) | `31.70% <0.00%> (-61.73%)` | :arrow_down: | | [...ompiler\_gym/service/client\_service\_compiler\_env.py](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch#diff-Y29tcGlsZXJfZ3ltL3NlcnZpY2UvY2xpZW50X3NlcnZpY2VfY29tcGlsZXJfZW52LnB5) | `68.89% <0.00%> (-22.52%)` | :arrow_down: | | [compiler\_gym/util/logging.py](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch#diff-Y29tcGlsZXJfZ3ltL3V0aWwvbG9nZ2luZy5weQ==) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | [compiler\_gym/wrappers/llvm.py](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch#diff-Y29tcGlsZXJfZ3ltL3dyYXBwZXJzL2xsdm0ucHk=) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | [compiler\_gym/util/flags/seed.py](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch#diff-Y29tcGlsZXJfZ3ltL3V0aWwvZmxhZ3Mvc2VlZC5weQ==) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | [compiler\_gym/util/statistics.py](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch#diff-Y29tcGlsZXJfZ3ltL3V0aWwvc3RhdGlzdGljcy5weQ==) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | [compiler\_gym/util/flags/nproc.py](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch#diff-Y29tcGlsZXJfZ3ltL3V0aWwvZmxhZ3MvbnByb2MucHk=) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | [compiler\_gym/util/permutation.py](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch#diff-Y29tcGlsZXJfZ3ltL3V0aWwvcGVybXV0YXRpb24ucHk=) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | [compiler\_gym/wrappers/\_\_init\_\_.py](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch#diff-Y29tcGlsZXJfZ3ltL3dyYXBwZXJzL19faW5pdF9fLnB5) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | [compiler\_gym/util/capture\_output.py](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch#diff-Y29tcGlsZXJfZ3ltL3V0aWwvY2FwdHVyZV9vdXRwdXQucHk=) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | ... and [88 more](https://codecov.io/gh/facebookresearch/CompilerGym/pull/775/diff?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=facebookresearch) | |