Type-based alias analysis

Abstract

This paper evaluates three alias analyses based on programming language types. The first analysis uses type compatibility to determine aliases. The second extends the first by using additional high-level information such as field names. The third extends the second with a flow-insensitive analysis. Although other researchers suggests using types to disambiguate memory references, none evaluates its effectiveness. We perform both static and dynamic evaluations of type-based alias analyses for Modula-3, a statically-typed type-safe language. The static analysis reveals that type compatibility alone yields a very imprecise alias analysis, but the other two analyses significantly improve alias precision. We use redundant load elimination (RLE) to demonstrate the effectiveness of the three alias algorithms in terms of the opportunities for optimization, the impact on simulated execution times, and to compute an upper bound on what a perfect alias analysis would yield. We show modest dynamic improvements for (RLE), and more surprisingly, that on average our alias analysis is within 2.5% of a perfect alias analysis with respect to RLE on 8 Modula-3 programs. These results illustrate that to explore thoroughly the effectiveness of alias analyses, researchers need static, dynamic, and upper-bound analysis. In addition, we show that for type-safe languages like Modula-3 and Java, a fast and simple alias analysis may be sufficient for many applications.

Expression-Based Aliasing for OO–languages

“…The proof follows immediately, by induction on the structure of p and Remark 2. Base cases are: create x, forget x and t : = s. For function calls, the result is a consequence of their corresponding unfolding, based on the definitions in (8).…”

Using Disjoint Reachability for Parallelization

“…Alias analysis [8][9][10] and pointer analysis [1,2], like disjoint reachability analysis, analyze source code to discover heap referencing properties. Aiken [11] is similar, but their type system names objects by allocation site and loop iteration.…”

“…Reachability from objects is essential and different from the reachability from variables discovered by alias analysis [8][9][10] -reachability from variables can only express a finite number of disjoint sets. Variable reachability cannot discover that an unbounded set of live data structures do not share objects.…”

Automatic Parallelization of C by Means of Language Transcription

“…Our model of pointer analysis is similar in many respects to the Type-Based Alias Analysis described by Diwan, McKinley and Moss [DMM98] for use with Modula-3. Their analysis is more general since it accommodates inherited types.…”

“…However, these low-level operations interfere with further optimizations such as parallelization, software pipelining and various types of loop transformations. Much research has been performed in the areas of pointer analysis [CWZ90,DMM98,GH95] and control-flow analysis to attempt to overcome the overhead of the conservative compilation techniques used to ensure correct semantics of execution in the presence of complicated expressions. Beyond correctness, the manner in which data is arranged in memory has major impacts on performance [BAM+96] due to architectural tendencies.…”