In computer science, instruction selection is the stage of a compiler backend that transforms its tree-based middle-level intermediate representation (IR) into a low-level IR very close to its final target language. In a typical compiler, it precedes both instruction scheduling and register allocation, so its output IR has an infinite set of pseudoregisters and may still be subject to peephole optimization; otherwise, it closely resembles the target machine code, bytecode, or assembly language. It works by "covering" the intermediate representation with as few tiles as possible. A tile is a template that matches a portion of the IR tree and can be implemented with a single target instruction.
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