: CompCertTSO: A Verified Compiler for Relaxed-Memory Concurrency. Jaroslav Ševčík, Viktor Vafeiadis, Francesco Zappa Nardelli, Suresh Jagannathan, and Peter Sewell. J. ACM, 60(3):22:1--22:50, June 2013. [ bib | doi | project page | pdf ]
In this article, we consider the semantic design and verified compilation of a C-like programming language for concurrent shared-memory computation on x86 multiprocessors. The design of such a language is made surprisingly subtle by several factors: the relaxed-memory behavior of the hardware, the effects of compiler optimization on concurrent code, the need to support high-performance concurrent algorithms, and the desire for a reasonably simple programming model. In turn, this complexity makes verified compilation both essential and challenging.
We describe ClightTSO, a concurrent extension of CompCert’s Clight in which the TSO-based memory model of x86 multiprocessors is exposed for high-performance code, and CompCertTSO, a formally verified compiler from ClightTSO to x86 assembly language, building on CompCert. CompCertTSO is verified in Coq: for any well-behaved and successfully compiled ClightTSO source program, any permitted observable behavior of the generated assembly code (if it does not run out of memory) is also possible in the source semantics. We also describe some verified fence-elimination optimizations, integrated into CompCertTSO.
: CompCert-TSO release, Version 1.12, Jaroslav Ševčík, Viktor Vafeiadis, Francesco Zappa Nardelli, Suresh Jagannathan, and Peter Sewell, August 2011. [ bib | project page | .html ]
: Relaxed-Memory Concurrency and Verified Compilation. Jaroslav Ševčík, Viktor Vafeiadis, Francesco Zappa Nardelli, Suresh Jagannathan, and Peter Sewell. In POPL 2011. [ bib | doi | project page | pdf ]
In this paper, we consider the semantic design and verified compilation of a C-like programming language for concurrent shared-memory computation above x86 multiprocessors. The design of such a language is made surprisingly subtle by several factors: the relaxed-memory behaviour of the hardware, the effects of compiler optimisation on concurrent code, the need to support high-performance concurrent algorithms, and the desire for a reasonably simple programming model. In turn, this complexity makes verified (or verifying) compilation both essential and challenging.
We define a concurrent relaxed-memory semantics for ClightTSO, an extension of CompCert's Clight in which the processor's memory model is exposed for high-performance code. We discuss a strategy for verifying compilation from ClightTSO to x86, which we validate with correctness proofs (building on CompCert) for the most interesting compiler phases.