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Re: criteria.html open issues
- To: dewar at gnat dot com, zackw at stanford dot edu
- Subject: Re: criteria.html open issues
- From: dewar at gnat dot com
- Date: Mon, 28 May 2001 08:24:26 -0400 (EDT)
- Cc: acahalan at cs dot uml dot edu, gcc at gcc dot gnu dot org
<<Reality injection: -fstrict-aliasing is enabled at -O2 in all
snapshots since 2.96, and will be in 3.0. It was turned off on the
2.95 branch to give people more time to fix their code. It is our
understanding that most free software projects have either fixed their
code or wired in a -fno-strict-aliasing where appropriate.
OK, thanks for injection, that makes perfect sense to me. Sory for
my previous messages based on incorrect information.
<<We'd want to look at tradeoffs between execution speed, executable
size, compiler speed, and ease of debugging; I'd suggest abandoning
the idea of 'levels of optimization' and instead tell the compiler
what you want to optimize for.
I disagree, you need reasonable defaults. Most programmers don't know enough
to understand what various optimizations do, or rather what their subtle
effects are when you take all the factors into effect (for instance most
programmers would not understand exactly what the issues are for loop
unrolling). Yes, you can ask programmers to experiment, and they will and
should if they need to extract max performance from a given appl, but it
is very useful to have general defaults.