Welcome back to compiler land. Today we’re going to talk about value numbering, which is like SSA, but more.

Lobsters is a community-driven platform for sharing and discussing links to articles, tutorials, and projects related to technology and programming. Readers can learn about a wide range of topics, from software development and system administration to cybersecurity and artificial intelligence. With user submissions, comments, and voting, Lobsters provides a platform for collaborative learning and knowledge sharing among technology enthusiasts.

Lobsters

A deep dive into value numbering as a compiler optimization technique. Covers local value numbering (LVN) for basic blocks using hash-consing, then extends to global value numbering (GVN) across control flow using dominator trees. Uses Maxine VM's Java implementation as a reference. Explains why pure vs. impure instructions matter, how phi-functions complicate loop handling, and how load-store forwarding can be integrated into GVN. Also surveys alternative approaches including unified hash tables, value partitioning, scoped hash maps (Cranelift), and worklist dataflow methods.

Value numbering