Peephole Optimization in Ruby VM: Adding opt_respond_to

This is part four of a series on optimizing the Ruby Virtual Machine (VM). The author delves into adding an `opt_respond_to` instruction to CRuby to optimize `respond_to?` method calls. The article details using a debugger to trace code execution, locate the peephole optimizer `iseq_peephole_optimize`, and by analyzing an existing frozen array optimization, attempts to match the pattern of `respond_to?` method calls, laying the groundwork for adding a new optimization instruction. The author uses concise code examples and debugging steps to clearly illustrate the peephole optimization mechanism and how to debug within the CRuby source code.