arXiv subjects

Vineeth Paleri

Publications and source records attributed to Vineeth Paleri.

4 recordsLinked to original sources

arXiv2022

Copy Propagation subsumes Constant Propagation

Constant propagation and copy propagation are code transformations that may avoid some load operations and can enable other optimizations. In literature, constant and copy propagations are considered two independent transformations requiring two different data flow analyses. Here we give a generic definition for copy propagation which enables us to view constant propagation as a particular case of copy propagation and formulate a novel data flow analysis that unifies these two transformations.

cs.PL↗

arXiv2018

A Note on "A polynomial-time algorithm for global value numbering"

Global Value Numbering(GVN) is a popular method for detecting redundant computations. A polynomial time algorithm for GVN is presented by Gulwani and Necula(2006). Here we present two limitations of this GVN algorithm due to which detection of certain kinds of redundancies can not be done using this algorithm. The first one is concerning the use of this algorithm in detecting some instances of the classical global common subexpressions, and the second is concerning its use in the detection of some redundancies that a local value numbering algorithm will detect. We suggest improvements that enable the algorithm to detect these kinds of redundancies as well.

cs.PL↗

arXiv2017

A fix-point characterization of Herbrand equivalence of expressions in data flow frameworks

The problem of determining Herbrand equivalence of terms at each program point in a data flow framework is a central and well studied question in program analysis. Most of the well-known algorithms for the computation of Herbrand equivalence in data flow frameworks proceed via iterative fix-point computation on some abstract lattice of short expressions relevant to the given flow graph. However the mathematical definition of Herbrand equivalence is based on a meet over all path characterization over the (infinite) set of all possible expressions. The aim of this paper is to develop a lattice theoretic fix-point formulation of Herbrand equivalence on the (infinite) concrete lattice defined over the set of all terms constructible from variables, constants and operators of a program. The present characterization uses an axiomatic formulation of the notion of Herbrand congruence and defines the (infinite) concrete lattice of Herbrand congruences. Transfer functions and non-deterministic assignments are formulated as monotone functions over this concrete lattice. Herbrand equivalence is defined as the maximum fix point of a composite transfer function defined over an appropriate product lattice of the above concrete lattice. A re-formulation of the classical meet-over-all-paths definition of Herbrand equivalence in the above lattice theoretic framework is also presented and is proven to be equivalent to the new lattice theoretic fix-point characterization.

cs.LO↗

arXiv2014

A Simple Algorithm for Global Value Numbering

Global Value Numbering(GVN) is a method for detecting redundant computations in programs. Here, we introduce the problem of Global Value Numbering in its original form, as conceived by Kildall(1973), and present an algorithm which is a simpler variant of Kildall's. The algorithm uses the concept of value expression - an abstraction of a set of expressions - enabling a representation of the equivalence information which is compact and simple to manipulate.

cs.PL↗