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Re: [dataflow][patch] Convert conflict graph to lower triangular bit matrix
- From: Joern RENNECKE <joern dot rennecke at st dot com>
- To: Peter Bergner <bergner at vnet dot ibm dot com>
- Cc: Kenneth Zadeck <zadeck at naturalbridge dot com>, Daniel Berlin <dberlin at dberlin dot org>, gcc-patches at gcc dot gnu dot org
- Date: Thu, 02 Feb 2006 16:33:51 +0000
- Subject: Re: [dataflow][patch] Convert conflict graph to lower triangular bit matrix
This is a very bad idea. The algorithm that examines conflicts is
quadratic in time. For functions with lots of registers, you get a very
large, sparce matrix. Using a symmetric matrix saves us a linear time
factor of about 64, since we can scan a row of the matrix one word at a
time.