[IR2Vec] Add llvm-ir2vec tool for generating triplet embeddings

[svkeerthy]

Add a new LLVM tool llvm-ir2vec. This tool is primarily intended to generate triplets for training the vocabulary (#141834) and to potentially generate the embeddings in a stand alone manner.

This PR introduces the tool with triplet generation functionality. In the upcoming PRs I'll add scripts under utils/mlgo to complete the vocabulary tooling. #147844 adds embedding generation logic to the tool.

(Tracking issue - #141817)

[svkeerthy]

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• [IR2Vec] Add embeddings mode to llvm-ir2vec tool #147844
• [IR2Vec] Add llvm-ir2vec tool for generating triplet embeddings #147842 👈 (View in Graphite)
• [NFC][IR2Vec] Exposing helpers in IR2Vec Vocabulary #147841
• [NFC][IR2Vec] Minor refactoring of opcode access in vocabulary #147585
• [IR2Vec] Restructuring Vocabulary #145119
• [IR2Vec] Add out-of-place arithmetic operators to Embedding class #145118
• [NFC][IR2Vec] Increasing tolerance in approximatelyEquals() of Embedding  #145117
• [IR2Vec] Simplifying creation of Embedder #143999
• [IR2Vec] Scale embeddings once in vocab analysis instead of repetitive scaling #143986
• [MLGO][IR2Vec] Integrating IR2Vec with MLInliner #143479 : 1 other dependent PR (#144139 )
• [IR2Vec] Consider only reachable BBs and non-debug instructions #143476
• [IR2Vec] Minor vocab changes and exposing weights #143200
• [IR2Vec] Exposing Embedding as an data type wrapped around std::vector<double> #143197
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[boomanaiden154]

The CI failures look relevant.

It would also be good to add a documentation file to the command guide. I would be fine with that happening in a separate patch though to keep the review focused.

Also, what's the point of generating these triplets? Nothing immediately springs to mind on how they would be useful.

[svkeerthy]

The CI failures look relevant.

Thanks! Looking into it.

It would also be good to add a documentation file to the command guide. I would be fine with that happening in a separate patch though to keep the review focused.

Yes, will add it in the next patch.

Also, what's the point of generating these triplets? Nothing immediately springs to mind on how they would be useful.

The triplets collected on various ll files act as the corpus for training the vocabulary. I shall add the helper scripts for training in the subsequent patches.