CacheIR: The Benefits of a Structured Representation for Inline Caches

Inline Caching is an important technique used to accelerate operations in dynamically typed language implementations by creating fast paths based on observed program behaviour. Most software stacks that support inline caching use low-level, often ad-hoc, Inline-Cache (ICs) data structures for code generation. This work presents CacheIR, a design for inline caching built entirely around an intermediate representation (IR) which: (i) simplifies the development of ICs by raising the abstraction level; and (ii) enables reusing compiled native code through IR matching techniques. Moreover, this work describesWarpBuilder, a novel design for a Just-In-Time (JIT) compiler front-end that directly generates type-specialized code by lowering the CacheIR contained in ICs; and Trial Inlining, an extension to the inline-caching system that allows for context-sensitive inlining of context-sensitive ICs. The combination of CacheIR and WarpBuilder have been powerful performance tools for the SpiderMonkey team, and have been key in providing improved performance with less security risk.