Imperative Program Transformation by Rewriting

Abstract

We present a method of specifying standard imperative program optimisations as a rewrite system. To achieve this we have extended the idea of matching sub-terms in expressions with simple patterns to matching blocks in a control flow graph. In order to express the complex restrictions on the applicability of these rewrites we add temporal logic side conditions. The combination of these features allows a flexible, high level, yet executable specification of many of the transformations found in optimising compilers.

Constructing component-based extension interfaces in legacy systems code

“…Patterns are described using formulas of a variant of the temporal logic CTL [9], allowing the description of complex, context-sensitive properties. A pattern is either a local pattern or a path pattern.…”

“…To allow interposing this support within existing function definitions, the rewrite rules use temporal logic to precisely describe rewriting sites in terms of control-flow patterns [1,9]. To facilitate evolution to new versions of the legacy code, these rewritings are performed using an automatic tool.…”

On the automatic evolution of an OS kernel using temporal logic and AOP

“…Temporal logic is commonly used to express properties of sequences of events, particularly in the context of model checking [8]. Our approach is inspired by that of Lacey et al, who use this logic to define rewrite rules that describe common compiler optimizations [9,10].…”

“…For this purpose, we use judgments of the form: n` where n is a node of the CFG and is a formula of temporal logic (specifically, a variant of CTL [9]). Formulas in this logic are as follows:…”

“…Lacey and de Moor use temporal logic to describe conditions on rewrite rules [9]. We follow their approach here.…”