Efficient Just-In-Time Execution of Dynamically Typed Languages Via Code Specialization Using Precise Runtime Type Inference

Dynamically typed languages such as JavaScript present a challenge to just-in-time compilers. In contrast to statically typed languages such as JVML, in which there are specific opcodes for common operations on primitive types (such as iadd for integer addition), all operations in dynamically typed language such as JavaScript are late-bound. Often enough, types cannot be inferred with certainty ahead of execution. As a result, just-in-time compilers for dynamically typed languages have tended to perform worse than their statically-typed counterparts. We present a new approach to compiling dynamically typed languages in which code traces observed during execution are dynamically specialized for each actually observed run-time type. For most benchmark programs, our prototype JavaScript virtual machine outperforms every other JavaScript platform known to us.