Re: A question about Dominators

vbdis@aol.com (VBDis)
20 Dec 2001 00:33:56 -0500

          From comp.compilers

Related articles
A question about Dominators rsherry8@home.com (Robert Sherry) (2001-12-15)
Re:A question about Dominators kvinay@ip.eth.net (kvinay) (2001-12-20)
Re: A question about Dominators vbdis@aol.com (2001-12-20)
Re: A question about Dominators Martin.Ward@durham.ac.uk (2001-12-20)
Re: A question about Dominators sweeks@acm.org (2001-12-20)
Re: A question about Dominators jeremy.wright@merant.com (Jeremy Wright) (2001-12-20)
| List of all articles for this month |

From: vbdis@aol.com (VBDis)
Newsgroups: comp.compilers
Date: 20 Dec 2001 00:33:56 -0500
Organization: AOL Bertelsmann Online GmbH & Co. KG http://www.germany.aol.com
References: 01-12-067
Keywords: analysis
Posted-Date: 20 Dec 2001 00:33:56 EST

"Robert Sherry" <rsherry8@home.com>schreibt:
>The basic idea of the first approach is that node a
>dominates node b if and only if a=b or a is the unique immediate predecessor
>of b or b has more then one immediate predecessor and for all immediate
>predecessors c of b, c is not equal to a and a dominates c.


IMO it's a matter of taste/convention, whether a node dominates itself
(a=b). But I definitely see no reason, why the dominator cannot be
one of multiple immediate predecessors.


In a graph with the edges (a,b), (a,c), (b,c) node a dominates both
nodes b and c.


So the idea should read:


Node a dominates node b if a=b, or for all immediate predecessors c of b, a
dominates c.


Now the case a=b also makes sense, since when node a is an immediate
predecessor of b, then node a dominates itself (as predecessor c of b). It's
not required that a<>c, and a single predecessor is only a special case of
multiple predecessors.


BTW, do you have an equivalent definition or idea for post-dominators?


DoDi


Post a followup to this message

Return to the comp.compilers page.
Search the comp.compilers archives again.