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TruffleRuby Compiler Intermediate Representation

1 post · Mar 2020 – Jun 2020

What this trail covers

Shopify is developing TruffleRuby, a JIT compiler for Ruby, and has implemented an optimization for the `||=` lazy initialization operator. This optimization leverages deoptimization to reduce machine code generation and improve compilation speed and memory usage. The system uses a custom `OrLazyValueDefinedNode` to handle the `||=` operator, making the deoptimization case the uncommon one where the variable needs to be assigned a value more than once. This optimization shows the benefit of looking at industry codebases for patterns not visible in language specifications. Shopify is also contributing to CRuby/MRI and Sorbet, and maintains Tapioca.

All Shopify trails
  1. Understanding Programs Using Graphs - ShopifyThis post introduces the 'sea-of-nodes' graph data structure as an intermediate representation used by the TruffleRuby JIT compiler. It explains the structure of these graphs, differentiating between control flow (red arrows) and data flow (green arrows), and operation types (square red for side-effects, diamond green for pure computation). Examples illustrate how graphs de-duplicate computations (global value numbering) and separate imperative and functional parts of a program. The post also discusses the challenges of visualizing large graphs and Shopify's ongoing work on tools to draw and decompile these graphs for Ruby code.
  2. Optimizing Ruby Lazy Initialization in TruffleRuby with Deoptimization - ShopifyImplemented an optimization for the `||=` lazy initialization operator in TruffleRuby by introducing an `OrLazyValueDefinedNode`. This node counts the number of times the else part of the `||=` expression is executed and turns it into a deoptimization if it's less than twice. This reduces machine code generation and improves compilation speed and memory usage. Benchmarking showed approximately 6% faster compilation and 63% less machine code by memory for specific code snippets.