GCC Middle and Back End API Reference
Data Fields
stmt_stats Struct Reference

Data Fields

int total
int total_phis
int removed
int removed_phis

Detailed Description

Dead code elimination pass for the GNU compiler. Copyright (C) 2002-2013 Free Software Foundation, Inc. Contributed by Ben Elliston bje@r.nosp@m.edha.nosp@m.t.com and Andrew MacLeod amacl.nosp@m.eod@.nosp@m.redha.nosp@m.t.co.nosp@m.m Adapted to use control dependence by Steven Bosscher, SUSE Labs.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see http://www.gnu.org/licenses/. Dead code elimination.

References:

Building an Optimizing Compiler, Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.

Advanced Compiler Design and Implementation, Steven Muchnick, Morgan Kaufmann, 1997, Section 18.10.

Dead-code elimination is the removal of statements which have no impact on the program's output. "Dead statements" have no impact on the program's output, while "necessary statements" may have impact on the output.

The algorithm consists of three phases:

  1. Marking as necessary all statements known to be necessary, e.g. most function calls, writing a value to memory, etc;
  2. Propagating necessary statements, e.g., the statements giving values to operands in necessary statements; and
  3. Removing dead statements.

Field Documentation

int stmt_stats::removed
int stmt_stats::removed_phis
int stmt_stats::total
int stmt_stats::total_phis
The documentation for this struct was generated from the following file: