Created
February 18, 2011 07:19
-
-
Save ishikawa/833372 to your computer and use it in GitHub Desktop.
A Simple, Fast Dominance Algorithm
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| # Cooper, Keith D.; Harvey, Timothy J.; and Kennedy, Ken (2001). A Simple, Fast Dominance Algorithm | |
| # http://www.cs.rice.edu/~keith/EMBED/dom.pdf | |
| # | |
| # Computing minimal SSA using dominance frontiers | |
| # http://en.wikipedia.org/wiki/Static_single_assignment_form#Computing_minimal_SSA_using_dominance_frontiers | |
| # | |
| # Dominator (graph theory) | |
| # http://en.wikipedia.org/wiki/Dominator_(graph_theory) | |
| # | |
| require 'set' | |
| class Node | |
| attr_reader :name, | |
| :predecessors, :successors, | |
| :dominance_frontiers | |
| attr_accessor :immediate_dominator | |
| def initialize(name) | |
| @name = name | |
| @immediate_dominator = nil | |
| @predecessors = [] | |
| @successors = [] | |
| @dominance_frontiers = Set.new | |
| end | |
| def <<(node) | |
| @predecessors << node | |
| node.successors << self | |
| node | |
| end | |
| def >>(node) | |
| @successors << node | |
| node.predecessors << self | |
| node | |
| end | |
| def ==(other) | |
| case other | |
| when self.class | |
| self.name == other.name | |
| else | |
| false | |
| end | |
| end | |
| def eql?(other) | |
| other.instance_of?(self.class) && self == other | |
| end | |
| end | |
| def simple_fast_dominance_algorithm(node) | |
| return unless node.predecessors.size >= 2 | |
| node.predecessors.each do |p| | |
| runner = p | |
| while runner != node.immediate_dominator | |
| runner.dominance_frontiers << node | |
| runner = runner.immediate_dominator | |
| end | |
| end | |
| end | |
| # 1 -----+ | |
| # | | | |
| # 2 <--+ | | |
| # 2 | | | |
| # +--- 2 ---+ | | |
| # | | | | |
| # | 3 <----+ | |
| # | | | |
| # +--> 4 | |
| node1 = Node.new(:node1) | |
| node2 = Node.new(:node2) | |
| node3 = Node.new(:node3) | |
| node4 = Node.new(:node4) | |
| # Connection | |
| node1 >> node2 >> node3 >> node4 | |
| node1 >> node3 | |
| node2 >> node2 | |
| node2 >> node4 | |
| # Immediate dominator | |
| node1.immediate_dominator = nil | |
| node2.immediate_dominator = node1 | |
| node3.immediate_dominator = node1 | |
| node4.immediate_dominator = node1 | |
| # Dominance frontiers | |
| [ node1, node2, node3, node4].each do |node| | |
| simple_fast_dominance_algorithm(node) | |
| end | |
| [ node1, node2, node3, node4].each do |node| | |
| simple_fast_dominance_algorithm(node) | |
| printf "%s --> %s\n", node.name, node.dominance_frontiers.map(&:name) | |
| end | |
| # node1 --> [] | |
| # node2 --> [:node2, :node3, :node4] | |
| # node3 --> [:node4] | |
| # node4 --> [] |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Hi - is this correct? :) because I might want to use it as my guide to implement in another language.