Re: gzip performance test

[David Edelsohn <dje at watson dot ibm dot com>]

	I do not think that gzip is a very useful performance test.  It
mainly is a question of how well GCC optimizes one loop.  The gzip part of
the GCC 3.0 release criteria was more about code quality and not
encoutering a regression, not about showing a large improvement.

	Using nbench / BYTEmark benchmark for powerpc-ibm-aix4.3.3.0

	GCC 2.95.3 gets:

MEMORY INDEX        : 1.699
INTEGER INDEX       : 2.205
FLOATING-POINT INDEX: 3.583

	GCC 3.0 prerelease gets:

MEMORY INDEX        : 1.748
INTEGER INDEX       : 2.683
FLOATING-POINT INDEX: 3.710

	IBM's XLC 3.6.6 gets:

MEMORY INDEX        : 1.830
INTEGER INDEX       : 2.294
FLOATING-POINT INDEX: 3.960

	All of this is un-scientific and not official results of any
kind.  By this comparison, gcc-3.0 looks pretty good at the basic C
optimization level.

	As usual, the real advice is use the compiler to test an
application that is representative of the type of work on which it will be
used.

	I know that a lot of people use gzip, but it is not a very broad
test.  gzip-1.2.4a does not show any regression on powerpc-ibm-aix4.3.3.0,
so I think it passes the code quality test.  I do not think that the x86
and PowerPC machine description improvements are stressed by gzip.

David