[mercury-users] gcc-3.3 on MacOS X Intel

[Peter Hawkins]

Hi...

On 8/17/07, Jonathan Morgan <jonmmorgan at gmail.com> wrote:
> On 8/18/07, Michael Day <mikeday at yeslogic.com> wrote:
> > Hi Tom,
> >
> > > I compiled mercury-compiler-rotd-2007-07-27 with gcc 4.0.1 on OS X
> > > 10.4.10, Intel by adding EXTRA_CFLAGS=-O0 to Mmake.params. There is a
> > > package for Mercury 0.13.1 in MacPorts (http://www.macports.org) but I
> > > haven't tried to install it.
> >
> > Does this mean that -O0 will be applied to programs compiled with the
> > Mercury compiler as well as the Mercury compiler itself? That sounds
> > like it could have scary performance implications.
>
> From memory, Mmake.params applies to the compiler, but not to programs
> compiled with the compiler.  Also note that this is C's O0.
> Presumably Mercury can still use any optimisation level it likes.  I
> would imagine that C's optimisations would not have as much effect on
> the final performance as Mercury's optimisations, but I'm not really
> sure.

I'm not sure exactly what gcc turns off with -O0, but it actually
might be a pretty large performance hit if it turns off things like
good register allocation.

Cheers,
Peter
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