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From: Jan Hubicka <hubicka@ucw.cz>
To: Marc Espie <espie@nerim.net>
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Subject: Re: gcc 3.5 integration branch proposal
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> On Sun, Jan 18, 2004 at 10:49:30PM -0500, David Edelsohn wrote:
> 
> > 	Did you build head configured with --disable-checking?
> 
> Rebuilt with --disable-checking, and double-checked the options. There
> was a bug that meant I was not -O2 in both cases.
> 
> Now, the actual options are 
> -Wall -Wstrict-prototypes -Wmissing-prototypes
> -Wno-uninitialized -Wno-format -Wno-main  -fno-builtin-printf
> -fno-builtin-log -fno-builtin-malloc -O2 -fno-strict-aliasing
> in both cases.
> 
> And it's still a bit slower:
> 
> gcc 3.3.2:
>   527.98s real   421.02s user    30.36s system
> 
> gcc -head  with --disable-checking:
>   544.91s real   439.52s user    30.27s system
> 
> 
> Okay, the slow-down is not as marked as with --enable-checking, but it
> still does exist: 4% is something.
> 
> Basically, the code there is just an OpenBSD kernel. It won't fly as a
> testcase unless you have an OpenBSD system available.
> 
> It's just plain old C.  Nothing really fancy about it.
> 
> So, the compiler is not getting faster.
> 
> To give you some scope, again. A similar bulk of code used to compile in
> 3 hours on a 68040.  This 4% translates to an extra 7 minutes.

Also if compilation speed is your major concern on older architectures,
you may consider disabling GCSE that consume about 6% of compilation
time at about 1-2% code quality improvements or even consider using -O1
everywhere, that one has generally better code quality/compilation time
tradeoffs.

Honza
> 
> A make build on such a machine takes about two days. This 4% translates to
> 2 hours more.
> 
> I'll try doing some profiling in the near future...