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Re: [GCC 3.x] Performance testing for QA
- From: dewar at gnat dot com (Robert Dewar)
- To: dewar at gnat dot com, kevina at gnu dot org
- Cc: Peter dot Sasi at t-systems dot co dot hu, aj at suse dot de, gcc at gcc dot gnu dot org,tjw at omnigroup dot com
- Date: Tue, 3 Sep 2002 16:55:25 -0400 (EDT)
- Subject: Re: [GCC 3.x] Performance testing for QA
<<The type of operations that encoder decoders use (lots of arithmetic and
data movement) should somehow be incorporate as a benchmark test gcc
should optimize for. The ideal goal would be to make the code fast enough
that hand written assembly would not be necessary. Thus using an encoder as
a benchmark would be beneficial. Even if it concentrates on tight loops.
>>
You need to remember that it is trivial to make a compiler make any ONE
simple program as fast as optimal assembly language.
How? Simply by recognizing the program, and saying "ah ha, this is program
number 234c, so replace it by the super efficient asm that Joe wrote".
Now of course doing things this blatantly would be considered cheating, but
in practice you can do things almost this outrageous in a much more
reserved and non-obvious way.
So a benchmark that has a single inner loop that takes most of the time
is almost always a bad idea.