XLA Interpreter Backend

The XLA Interpreter backend operates at HLO-level by ingesting a HloModule and evaluating the result of the HLO graph directly with HloEvaluator, without lowering it further (to LLVM IR for example) before execution as other backends (CPU and GPU for example) do.

Its key components are:

• [InterpreterCompiler] despite the inherited naming of "compiler", all InterpreterCompiler really does is the following:
  1. Runs certain HLO optimization passes on the given HLO graph.
  2. Generates an InterpreterExecutable from the optimized HLO graph.
  3. Registers itself in the global compiler factory registry.
• [InterpreterExecutable]: responsible for running input HLO graph through the HloEvaluator, allocating output buffer and finally copying evaluated Literal result over.
• [HloEvaluator]: traverses a HLO graph and evaluates each node in DFS ordering along the way.