Enabling Sparse Constant Propagation of Array Elements via Array SSA Form

  • Vivek Sarkar
  • Kathleen Knobe
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1503)

Abstract

We present a new static analysis technique based on Array SSA form [6]. Compared to traditional SSA form, the key enhancement in Array SSA form is that it deals with arrays at the element level instead of as monolithic objects. In addition, Array SSA form improves the φ function used for merging scalar or array variables in traditional SSA form. The computation of a φ function in traditional SSA form depends on the program’s control flow in addition to the arguments of the φ function. Our improved φ function (referred to as a φ function) includes the relevant control flow information explicitly as arguments through auxiliary variables that are called @ variables.

The @ variables and φ functions were originally introduced as run-time computations in Array SSA form. In this paper, we use the element-level φ functions in Array SSA form for enhanced static analysis. We use Array SSA form to extend past algorithms for Sparse Constant propagation (SC) and Sparse Conditional Constant propagation (SCC) by enabling constant propagation through array elements. In addition, our formulation of array constant propagation as a set of data flow equations enables integration with other analysis algorithms that are based on data flow equations.

Keywords

static single assignment (SSA) form constant propagation conditional constant propagation Array SSA form unreachable codeelimination 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • Vivek Sarkar
    • 1
  • Kathleen Knobe
    • 2
  1. 1.IBM Thomas J. Watson Research CenterYorktown HeightsUSA
  2. 2.Compaq Cambridge Research LaboratoryCambridgeUSA

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