Sign In

Communications of the ACM

Research highlights

Practical Verification of Peephole Optimizations with Alive


Practical Verification of Peephole Optimizations with Alive, illustration

Compilers should not miscompile. Peephole optimizations, which perform local rewriting of the input program to improve the efficiency of generated code, are a persistent source of compiler bugs. We created Alive, a domain-specific language for writing optimizations and for automatically either proving them correct or else generating counterexamples. Furthermore, Alive can be automatically translated into C++ code that is suitable for inclusion in an LLVM optimization pass. Alive is based on an attempt to balance usability and formal methods; for example, it captures—but largely hides—the detailed semantics of the various kinds of undefined behavior. Alive has found numerous bugs in the LLVM compiler and is being used by LLVM developers.

Back to Top

1. Introduction

Compiler optimizations should be efficient, effective, and correct—but meeting all of these goals is difficult. In practice, whereas efficiency and effectiveness are relatively easy to quantify, correctness is not. Incorrect compiler optimizations can remain latent for long periods of time; the resulting problems are subtle and difficult to diagnose since the incorrectness is introduced at a level of abstraction lower than the one where software developers typically work.

Random testing7, 20 is one approach to improving the correctness of compilers; it has been shown to be effective, but of course testing misses bugs. A stronger form of insurance against compiler bugs can be provided by a proof that the compiler is correct (compiler verification) or a proof that a particular compilation was correct (translation validation). The state of the art in compiler verification requires a fresh compiler implementation and many person-years of proof engineering (e.g., CompCert9), making this appoach impractical in most production environments.


 

No entries found

Log in to Read the Full Article

Sign In

Sign in using your ACM Web Account username and password to access premium content if you are an ACM member, Communications subscriber or Digital Library subscriber.

Need Access?

Please select one of the options below for access to premium content and features.

Create a Web Account

If you are already an ACM member, Communications subscriber, or Digital Library subscriber, please set up a web account to access premium content on this site.

Join the ACM

Become a member to take full advantage of ACM's outstanding computing information resources, networking opportunities, and other benefits.
  

Subscribe to Communications of the ACM Magazine

Get full access to 50+ years of CACM content and receive the print version of the magazine monthly.

Purchase the Article

Non-members can purchase this article or a copy of the magazine in which it appears.
Sign In for Full Access
» Forgot Password? » Create an ACM Web Account