Concurrent Circular Reference Attribute Grammars (Extended Version)

Reference Attribute Grammars (RAGs) is a declarative executable formalism used for constructing compilers and related tools. Existing implementations support concurrent evaluation only with global evaluation locks. This may lead to long latencies in interactive tools, where interactive and background threads query attributes concurrently.

We present lock-free algorithms for concurrent attribute evaluation, enabling low latency in interactive tools. Our algorithms support important extensions to RAGs like circular (fixed-point) attributes and higher-order attributes.

We have implemented our algorithms in Java, for the JastAdd metacompiler. We evaluate the implementation on a JastAdd-specified compiler for the Java language, demonstrating very low latencies for interactive attribute queries, on the order of milliseconds. Furthermore, initial experiments show a speedup of about a factor 2 when using four parallel compilation threads.