The speed of the compiler, was: Re: Combine four insns
Toon Moene
toon@moene.org
Tue Aug 10 13:02:00 GMT 2010
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
Saturnushof 14, 3738 XG Maartensdijk, The Netherlands
At home: http://moene.org/~toon/; weather: http://moene.org/~hirlam/
Progress of GNU Fortran: http://gcc.gnu.org/gcc-4.5/changes.html#Fortran
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