Re: The speed of the compiler, was: Re: Combine four insns

[Toon Moene <toon at moene dot org>]

Chris Lattner wrote:

> On Aug 9, 2010, at 10:28 AM, Toon Moene wrote:
>
> > Diego Novillo wrote:
> >
> > > On 10-08-09 13:07 , Toon Moene wrote:
> > > > Is this also true for C++ ? In that case it might be useful to curb
> > > > Front End optimizations when -O0 is given ...
> > > Not really, the amount of optimization is quite minimal to non-existent.
> > > Much of the slowness is due to the inherent nature of C++ parsing. There is some performance to be gained by tweaking the various data structures and algorithms, but no order-of-magnitude opportunities seem to exist.
> > Perhaps Chris can add something to this discussion - after all, LLVM is written mostly in C++, no ?
> >
> > Certainly, that must have provided him (and his team) with boatloads of performance data ....
>
> I'm not sure what you mean here.  The single biggest win I've got in my personal development was
> switching from llvm-g++ to clang++.  It is substantially faster, uses much less memory and
> has better QoI than G++.  I assume that's not the option that you're suggesting though. :-)

Well, I just hoped for a list of things where clang++ was faster than 
llvm-g++ and why, but the issues you addressed are probably just as well ...

Thanks,

[ It would probably also help if we started to build GCC with C++ by
  default, although I imagine that the code isn't C++-like enough
  to guide us through all the issues ]

--
Toon Moene - e-mail: toon@moene.org - phone: +31 346 214290
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