floor operation problem

[Marco Leise]

Am Thu, 19 Dec 2013 14:54:56 +0100
schrieb "bearophile" <bearophileHUGS at lycos.com>:

> David Nadlinger:
> 
> > I don't think Marco is building his C executable with 
> > -ffast-math.
> 
> Showing the asm is a good way to understand what's going on in 
> those 64 bit builds.
> 
> 
> > We should definitely be able to provide a switch to enable the 
> > same unsafe/wrong FP optimizations in LDC as well.
> 
> So is this floor problem caused by those (missing) FP 
> optimizations? :-)
> 
> Bye,
> bearophile

At first my gcc executable had the same speed as on your
computer, bearophile (~1s). Then I removed some of the flags
including -ffast-math from the gcc command-line and it became
25% faster -> 0.8s. I didn't try your original ldmd2
command-line, but one from a generic "omg-uber-optimize"
Makefile I often use for stuff like this and immediately had
the same performance in D as for C. I cannot show you the
disassembly though, I'm in the middle of upgrading to to Gnome
3 and most programs don't work, like e.g. copy&paste from
terminals.

-- 
Marco