[Texmacs-dev] Re: TeXmacs 1.0-1 -ffloat-store [Q]

[Joris van der Hoeven]

> > > >     CONFIG_CXXFLAGS="-m68020-60"
> > > 
> > > how about "-fno-exceptions -fno-rtti -fno-implicit-templates" ? 
> > > They should be the same like on any other Linux machine and
> > > afaics make sense.
> > 
> > We do not longer use "-fno-rtti -fno-implicit-templates" since
> > version 1.0.0.10 and "-fno-exceptions" will be added automatically.
> 
> any pros/cons of rtti? I would imagine it just wastes memory if
> you aren't using it.

I don't know; David told me that he had to remove it for some reason.

> > > -m68020-60 is not strictly needed and as long configure does
> > > honour normal CFLAGS its better let the user specify the
> > > CPU variant.
> > 
> > OK, so I will leave it out.
> > 
> > > >     CONFIX_CXXOPTIMIZE="-O2 -ffloat-store"
> > > 
> > > I think '-ffloat-store' is definitively not needed.
> > 
> > Why did someone put it in the TeXmacs.spec then...?
> > What is it supposed to do?
> > Did you do some benchmarking in order to find out?
> 
> <<gcc manual>>
> `-ffloat-store'
>      Do not store floating point variables in registers, and inhibit
>      other options that might change whether a floating point value is
>      taken from a register or memory.
> 
>      This option prevents undesirable excess precision on machines such
>      as the 68000 where the floating registers (of the 68881) keep more
>      precision than a `double' is supposed to have.  Similarly for the
>      x86 architecture.  For most programs, the excess precision does
>      only good, but a few programs rely on the precise definition of
>      IEEE floating point.  Use `-ffloat-store' for such programs, after
>      modifying them to store all pertinent intermediate computations
>      into variables.
> 
> I can hardly believe TeXmacs would rely on something like this
> and so far it works fine without it, the speed impact would be 
> certainly noticeable for heavy fp oriented programs, esp on older
> CPUs with less than perfect caching.

OK, the option will be removed.

> > >   - toolbar and maybe complete window gets redrawn after every cursor 
> > >     movement etc. Mostly not really noticeable except some extra
> > >     flicker.
> > 
> > Yes, we probably should use some backing store here.
> 
> no need for backing store when there is nothing to redraw?

True, I forgot to tell you that one, but it is somehow quite involved.

Thanks for your help. Please test the 1.0.0.11 distribution
when it will be out.

<Joris>