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Re: i386 inline-asm string functions - some questions
On Sun, Dec 28, 2003 at 09:55:33PM -0800, Zack Weinberg wrote:
>
> > > ... however, that advantage is only theoretical. Experiments such as
> > > Peter Zaitsev's just now, and mine several years ago, demonstrate that
> > > the bits/string.h and bits/string2.h inlines make code worse, not better.
> > > Therefore they should be removed.
> >
> > Funny, I conducted this experiment last week and found quite the
> > opposite. Compiling the demangler and a smallish yacc parser
> > with -D__NO_STRING_INLINES cost about 20% in runtime.
>
> That's interesting. My testing was with much larger programs where
> str* / mem* aren't the bottleneck anyway. I wonder if you would be
> willing to take a look at the differences in the assembly language
> and see where that 20% is coming from.
Sorry; I tried, but there were so many differences that I couldn't
characterize it. If you care enough to try yourself, check out
drow-cplus-branch for GDB, configure, and make -C gdb test-cpnames.
cp-names-main.tab.o is the object of interest.
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer