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Re: 100x perfomance regression between gcc 3.4.5 and gcc 4.X
On 3/12/06, Ernest L. Williams Jr. <ernesto@ornl.gov> wrote:
> On Sun, 2006-03-12 at 15:17 +0100, Richard Guenther wrote:
> > On 3/12/06, Ernest L. Williams Jr. <ernesto@ornl.gov> wrote:
> > > > In any case: memcpy/memset inlining is broken in current GCC at least
> > > > on athlon arch.
> >
> > let's say it changed. Also memcpy/memset "inlining" is not regular inlining
> > but driven by completely different heuristics.
> >
> > > Yes, why is the benchmark not valid?
> > > Then we would appreciate if the developers could recommend a valid test.
> >
> > What is the benchmark supposed to measure?
>
> The following is from the website mentioned previously:
> =============================================================================
>
> What does it benchmark?
I asked about the specific benchmark, I guess
> Bashmark is testing the things that most applications need. It is trying
> to show you how well your hardware works together.
> Currently the things which are being tested are:
> -Calculations with types of different range
> -Calculations with floating point types of different range
> -Read and write into the memory with different size.
this one should be measured. But note that the benchmark is a
no-op and can be validly optimizes to int main() { return 0; } by the
compiler. This is why I call it a stupid benchmark. Also you are
measuring exclusively cache performance.
Richard.