Re: old register allocators by coloring
15 Dec 2001 00:36:08 -0500

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old register allocators by coloring (Sid Ahmed Ali TOUATI) (2001-11-25)
Re: old register allocators by coloring (2001-12-15)
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Newsgroups: comp.compilers
Date: 15 Dec 2001 00:36:08 -0500
Organization: University of California, Riverside
References: 01-11-108
Keywords: registers, optimize
Posted-Date: 15 Dec 2001 00:36:08 EST

Sid Ahmed Ali TOUATI <> wrote:
: My question is about the coloring methods (Chaitin, Chow, etc...) for
: register allocation. They generally make at first a live range
: analysis step to build an interference graph. After, they try to color
: it with some heuristics. I don't understand why they use heuristics
: here : if we assume some live range schemes, so we have live
: intervals. We can buid an interval graph : looking for a maximal
: clique is not NP-complete in such a graph (and hence the dual coloring
: problem is also easy). Why do they use heuristics here ?

In general, the problem of telling whether or not a graph contains a
k-node clique is NP-complete. Finding a maximal clique solves the
problem of telling whether there is a k-clique, so finding a maximal
clique is as hard. (I think this is covered in the book by Gary and

Tom Payne

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