Looking Into Peephole Optimizations
summary
Shows how Ruby applies peephole rewrites inside compile.c using RubyVM::InstructionSequence and the ISeq_peep_optimize pass, finding about 20–30 hardcoded patterns. Demonstrates concrete gains: combining range creation is 5.4× faster, removing a needless splat is 1.31×, replacing array dup with putobject is 1.26×, plus smaller instruction counts and reduced memory. Includes microbenchmarks with whyjitbench and links to YARV docs and the PR that swapped duparray for putobject.
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chapters (4)
- 0:00Start
- 13:57Removing unnecessary instructions
- 16:30Removing redundant instructions
- 23:39Ruby is a dynamic language, so it's hard to get information at compile time.
