Related articles |
---|
Is register allocation really NP-Complete? payne@zeus.unomaha.edu (1991-03-26) |
Re: Is register allocation really NP-Complete? larus@cs.wisc.edu (1991-03-27) |
Re: Is register allocation really NP-Complete? preston@ariel.rice.edu (1991-03-27) |
Re: Is register allocation really NP-Complete? david@cs.washington.edu (1991-03-27) |
Re: Is register allocation really NP-Complete? preston@ariel.rice.edu (1991-03-28) |
Re: Is register allocation really NP-Complete? spencert@cs.rpi.edu (1991-03-31) |
Newsgroups: | comp.compilers |
From: | david@cs.washington.edu (David Callahan) |
Keywords: | optimization, theory, design |
Organization: | Tera Computer Co., Seattle WA |
References: | <11422.27ef7017@zeus.unomaha.edu> |
Date: | 27 Mar 91 16:01:36 GMT |
In article <11422.27ef7017@zeus.unomaha.edu> payne@zeus.unomaha.edu (Matt Payne) writes:
>
>So, I'm confused. [Chow 90] implies that this is a NP-complete problem,
>but how can it be if [Chow 90]'s interference graphs are interval
>graphs?
Conflict graphs, even coarse ones such as Chow constructs, are not
interval graphs. Consider the fragment:
A =
B =
l: ... = B
... = A
C =
...
... = C
B =
goto l;
... A
Note that the live range of B is discontiguous due to the control flow.
These live ranges might be viewed as:
BB CCC B
AAAAAAAAAAA
and so we see the conflict graph is not an interval graph.
However, I don't know of a method that shows how to construct a program
whose conflict graph corresponds to some arbitrary graph and so it is
still possible that the restricted coloring problem associated with
conflict graphs is not NP-hard.
--
David Callahan (david@tera.com, david@june.cs.washington.edu,david@rice.edu)
Tera Computer Co. 400 North 34th Street Seattle WA, 98103
--
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