This paper reports on the design, implementation, and empirical results of a new method for dealing with the aliasing problem in C. The method is based on approximating the points-to relationships between accessible stack locations, and can be used to generate alias pairs, or used directly for other analyses and transformations. Our method provides context-sensitive interprocedural information based on analysis over invocation graphs that capture all calling contexts including recursive and mutually-recursive calling contexts. Furthermore, the method allows the smooth integration for handling general function pointers in C.

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 optimizations like common subexpression elimination, loop...

We present the design of DyC, a dynamic-compilation system for C based on run-time specialization. Directed by a few declarative user annotations that specify the variables and code on which dynamic compilation should take place, a binding-time analysis computes the set of run-time constants at each program point in the annotated procedure's control-flow graph; the analysis supports program-point-specific polyvariant division and specialization. The results of the analysis guide the construction of a run-time specializer for each dynamically compiled region; the specializer supports various caching strategies for managing dynamically generated code and mixes of speculative and demand-driven specialization of dynamic branch successors. Most of the key cost/benefit trade-offs in the binding-time analysis and the run-time specializer are open to user control through declarative policy annotations. DyC has

this paper is structured in the following way: a thorough description of the structure of a decompiler, followed by the description of our implementation of an # An idiom is a sequence of instruction that forms a logical entity and has a meaning that cannot be derived by considering the primary meanings of the individual instructions # # # # HLL program (language dependent) Back-end (analysis) UDM (machine dependent) Front-end binary program Figure 1. Decompiler modules automatic decompiling system, and conclusions. The paper is followed by the definitions of graph theoretical concepts used throughout the paper (Appendix I), and sample output from different phases of the decompilation of a program (Appendix II)

This paper presents a practical heap analysis technique, connection analysis, that can be used to disambiguate heap accesses in C programs. The technique is designed for analyzing programs that allocate many disjoint objects in the heap such as dynamically-allocated arrays in scientific programs. The method statically estimates connection matrices which encode the connection relationships between all heap-directed pointers at each program point. The results of the analysis can be used by parallelizing compilers to determine when two heapallocated objects are guaranteed to be disjoint, and thus can be used to improve array dependence and interference analysis. The method has been implemented as a context-sensitive interprocedural analysis in the McCAT optimizing/parallelizing C compiler. Experimental results are given to compare the accuracy of connection analysis versus a conservative estimate based on points-to analysis. This work supported by NSERC, FCAR, and the EPPP project (fin...

We present the design of a dynamic compilation system for C. Directed by a few declarative user annotations specifying where and on what dynamic compilation is to take place, a binding time analysis computes the set of run-time constants at each program point in each annotated procedure's control flow graph; the analysis supports program-point-specific polyvariant division and specialization. The analysis results guide the construction of a specialized run-time specializer for each dynamically compiled region; the specializer supports various caching strategies for managing dynamically generated code and supports mixes of speculative and demand-driven specialization of dynamic branch successors. Most of the key cost/benefit trade-offs in the binding time analysis and the run-time specializer are open to user control through declarative policy annotations. Our design is being implemented in the context of an existing optimizing compiler.

Since a binding-time analysis determines how an off-line partial evaluator will specialize a program, the accuracy of the binding-time information directly determines the degree of specialization. We have designed and implemented a binding-time analysis for an imperative language, and integrated it into our partial evaluator for C, called Tempo [11]. This binding-time analysis includes a number of new features, not available in any existing partial evaluator for an imperative language, which are critical when specializing existing programs such as operating system components [27,28]. ffl Flow sensitivity. A different binding-time description is computed for each program point, allowing the same variable to be considered static at one program point and dynamic at another. ffl Context sensitivity. Each function call is analyzed with the context of the call site, generating multiple binding-time annotated instances of the same function definition. ffl Return sensitivity. A different bi...

This paper reports on the design and implementation of a practical shape analysis for C. The purpose of the analysis is to aid in the disambiguation of heap-allocated data structures by estimating the shape (Tree, DAG, or Cyclic Graph) of the data structure accessible from each heap-directed pointer. This shape information can be used to improve dependence testing and in parallelization, and to guide the choice of more complex heap analyses. The method has been implemented as a contextsensitive interprocedural analysis in the McCAT compiler. Experimental results and observations are given for 16 benchmark programs. These results show that the analysis gives accurate and useful results for an important group of applications. 1 Introduction and Related Work Pointer analyses are of critical importance for optimizing /parallelizing compilers that support languages like C, C++ and FORTRAN90. The pointer analysis problem can be divided into two distinct subproblems: (i) analyzing pointers t...

This paper presents algorithms for reducing the communication overhead for parallel C programs that use dynamically-allocated data structures. The framework consists of an analysis phase called possible-placement analysis, and a transformation phase called communication selection. The fundamental idea of possible-placement analysis is to find all possible points for insertion of remote memory operations. Remote reads are propagated upwards, whereas remote writes are propagated downwards. Based on the results of the possible-placement analysis, the communication selection transformation selects the "best" place for inserting the communication, and determines if pipelining or blocking of communication should be performed. The framework has been implemented in the EARTH-McCAT optimizing/parallelizing C compiler, and experimental results are presented for five pointerintensive benchmarks running on the EARTH-MANNA distributed-memory parallel architecture. These experiments show that the...

. Generalized Constant Propagation (GCP) statically estimates the ranges of variables throughout a program. GCP is a top-down compositional compiler analysis in the style of abstract intepretation. In this paper we present an implementation of both intraprocedural and interprocedural GCP within the context of the C language. We compare the accuracy and utility of GCP information for several versions of GCP using experimental results from an actual implementation. 1 Introduction Generalized Constant Propagation (GCP) is a top-down compositional compiler analysis based on the style of abstract interpretation [CC77]. A GCP analysis statically approximates the possible values each variable could take at each point in the program. As an extension of constant propagation (CP), GCP estimates ranges for variables rather than their precise value: each variable at each point is associated with a minimum and maximum value. We have implemented GCP for the full C language, in both intraprocedural...