Semantic foundations for typed assembly languages

Amal Ahmed, Andrew W. Appel, Christopher D. Richards, Kedar N. Swadi, Gang Tan, Daniel C. Wang

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Typed Assembly Languages (TALs) are used to validate the safety of machine-language programs. The Foundational Proof-Carrying Code project seeks to verify the soundness of TALs using the smallest possible set of axioms: the axioms of a suitably expressive logic plus a specification of machine semantics. This article proposes general semantic foundations that permit modular proofs of the soundness of TALs. These semantic foundations include Typed Machine Language (TML), a type theory for specifying properties of low-level data with powerful and orthogonal type constructors, and Lc, a compositional logic for specifying properties of machine instructions with simplified reasoning about unstructured control flow. Both of these components, whose semantics we specify using higher-order logic, are useful for proving the soundness of TALs. We demonstrate this by using TML and Lc to verify the soundness of a low-level, typed assembly language, LTAL, which is the target of our core-ML-to-sparc compiler. To prove the soundness of the TML type system we have successfully applied a new approach, that of step-indexed logical relations. This approach provides the first semantic model for a type system with updatable references to values of impredicative quantified types. Both impredicative polymorphism and mutable references are essential when representing function closures in compilers with typed closure conversion, or when compiling objects to simpler typed primitives.

Original languageEnglish (US)
Article number1709094
JournalACM Transactions on Programming Languages and Systems
Issue number3
StatePublished - Mar 1 2010

All Science Journal Classification (ASJC) codes

  • Software


  • Control flow
  • Logical relations
  • Proof-carrying code
  • Semantic models
  • Typed assembly languages


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