Putting pointer analysis to work

Abstract

This paper addresses the problem of how to apply pointer analysis to a wide variety of compiler applications. We are not presenting a new pointer analysis. Rather, we focus on putting two existing pointer analyses, points-to analysis and connection analysis, to work. We demonstrate that the fundamental problem is that one must be able to compare the memory locations read/written via pointer indirections, at different program points, and one must also be able to summarize the effect of pointer references over regions in the program. It is straightforward to compute read/write sets for indirections involving stack-directed pointers using points-to information. However, for heap-directed pointers we show that one needs to introduce the notion of anchor handles into the connection analysis and then express read/write sets to the heap with respect to these anchor handles. Based on the read/write sets we show how to extend traditional analyses like common subexpression elimination, loop-invariant removal and location-invariant removal to include pointer references. We also demonstrate the use of our information on more advanced techniques such as array dependence testing and program understanding. We have implemented our techniques in our McCAT C compiler, and we demonstrate examples of applying our methods on a set of pointer-intensive C benchmarks, as well as present concrete empirical data on the improvements achieved.