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Table of Contents

Introduction

• In this module, students continue on compiler background materials on liveness analysis.
• The module also reviews SSA and provides an overview of other compiler optimizations.
• It also provides an overview of GPU branch divergence analysis.

Objectives

• Perform liveness analysis on loops.
• Understand SSA.

Readings

Required

Optional

Notes / Things that stand out

Live Variable Analysis

• Liveness analysis helps determine which variables are live (in use) at various program points during code execution.
• Usage: Register Allocation.
  • Register is allocated only for live variables.
  • This optimizes register spills, and therefore enhances overall performance.

Dataflow Equations

• $def_B$ : Set of variables defined in block B before any use.
• $use_B$ : Set of variables whose values may be used in block B before any definition.
• $IN[EXIT] = \phi$ : Boundary condition.