Adds support to run `.mlir` LIT tests in bazel.
```
bazel test @torch-mlir//test/...
```
Follow-on PR will contain these updates:
- Add tests to GHA CI workflow
- Add `.py` LIT tests to bazel
This introduces a new pass LowerToBackendContract (better name very
welcome) which performs the bulk of the simplifications that we do,
such as
- shape refinement
- dtype refinement
- maximizing value semantics
- inlining global slots
- decomposing complex ops
The key difference from before is that it iterates the set of
transformations, which can help to break a number of "catch-22" issues
where one simplification depends on another, the latest example being
here:
https://github.com/llvm/torch-mlir/issues/1131
This also exposed that RefineTypes was sometimes crashing/asserting for
certain inputs. This commit hardens it a bit.
The torch-mlir bazel build is [failing](https://github.com/llvm/torch-mlir/runs/7737425906?check_suite_focus=true) since [this commit](504de5e701) due to a linker failure (undefined symbol: `mlir::torch::Torch::createEraseModuleInitializerPass()`).
```
ERROR: /home/runner/.cache/bazel/_bazel_runner/db599744cd37f8c161e5034d9b9cd520/external/torch-mlir/BUILD.bazel:845:10: Linking external/torch-mlir/torch-mlir-opt failed: (Exit 1): clang failed: error executing command /usr/lib/llvm-11/bin/clang @bazel-out/k8-fastbuild/bin/external/torch-mlir/torch-mlir-opt-2.params
Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
ld.lld: error: undefined symbol: mlir::torch::Torch::createEraseModuleInitializerPass()
>>> referenced by Passes.cpp
>>> bazel-out/k8-fastbuild/bin/external/torch-mlir/_objs/TorchMLIRTorchPasses/Passes.pic.o:(mlir::torch::Torch::createTorchFunctionToTorchBackendPipeline(mlir::OpPassManager&, mlir::torch::Torch::TorchLoweringPipelineOptions const&))
>>> referenced by Passes.cpp
>>> bazel-out/k8-fastbuild/bin/external/torch-mlir/_objs/TorchMLIRTorchPasses/Passes.pic.o:((anonymous namespace)::registerEraseModuleInitializerPass()::'lambda'()::operator()() const)
clang: error: linker command failed with exit code 1 (use -v to see invocation)
```
This PR adds `lib/Dialect/Torch/Transforms/EraseModuleInitializer.cpp` to `TorchMLIRTorchPasses` library.
A previous patch added a new file
("VerifyConversionToValueSemantics.cpp") to the build, but it did not
add it to the list files known to bazel. This patch fixes the problem.
Sambhav Jain
Ahmed S. Taei
Vivek Khandelwal
Tanyo Kwok
Sean Silva
Ramana Radhakrishnan
武家伟
Ashay Rane
Maksim Levental