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Re: Apple's -fast option for gcc

On Tuesday, September 16, 2003, at 11:15 PM, Andreas Jaeger wrote:
The question is whether Apple likes to add -fast to GCC.  IMO -fast
should enable all flags that help a specific set of benchmarks, the
flags are target dependand.

In the end, we'd like -O2 or -O3 to subsume and contain most of it. In the beginning, we implement interesting new things, usually control them via flags, so that we can tell what is working and what isn't, to be able to try a multitude of various options and see what combination gives what type of improvements, and then we put the ones that work out under fast. Kinda like a hat hook, we just hang code there. Also, SPEC doesn't want a command line that wraps 40 times... :-) I'd expect that the good ideas that don't have abi impact or language impacts to eventually be in O2 or O3. Some of them won't ever go into -On. An example of this would be -mdynamic-no-pic, it is used to specific that the code that we compile, isn't going to go into a shared library, the default being, the code _can_ go into a shared library. This isn't ever appropriate for -O2 or -O3, it is a different shape, like -fPIC, or -static.

-fast is very, very small. It just turns on 5-25 other, existing flags. There isn't a reason why it could not be contributed. Do others want it? It is _good_ for SPEC. That is the intent and the primary purpose. It may give people ideas on what things may help certain types of programs, but, like any benchmark, your mileage may vary. I don't think we were going to submit it, rather, all the work under it, and hopefully, get that into other options, or new options, as appropriate. Another option besides -fast, would be for the documentation for the compiler to give the current, best known SPEC flags.

Disclaimer, I don't work on -fast, so I may have some details wrong. I've been working on making the compiler fast. :-)

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