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Re: [patch cygwin]: Replace inline-assembler in string.h by C implementation


On Oct 24 18:02, Kai Tietz wrote:
> 2012/10/24 Christopher Faylor wrote:
> > On Wed, Oct 24, 2012 at 11:07:47AM -0400, Ryan Johnson wrote:
> >>On 24/10/2012 5:16 AM, Kai Tietz wrote:
> >>> Hello,
> >>>
> >>> this patch replaces the inline-assember used in string.h by C implementation.
> >>> There are three reasons why I want to suggest this.  First, the C-code might
> >>> be optimized further by fixed (constant) arguments.  Secondly, it is
> >>> architecture
> >>> independent and so we just need to maintain on code-path.  And as
> >>> third point, by
> >>> inspecting generated assembly code produced by compiler out of C code
> >>> vs. inline-assembler
> >>> it shows that compiler produces better code.  It handles
> >>> jump-threading better, and also
> >>> improves average executed instructions.
> >>Devil's advocate: better-looking code isn't always faster code.
> >>
> >>However, I'm surprised that code was inline asm in the first place -- no
> >>special instructions or unusual control flow -- and would not be at all
> >>surprised if the compiler does a better job.
> >>
> >>Also, the portability issue is relevant now that cygwin is starting the
> >>move toward 64-bit support.
> >
> > Yes, that's exactly why Kai is proposing this.
> >
> > I haven't looked at the code but I almost always have one response to
> > a "I want to rewrite a standard function" patches:
> >
> > Have you looked at other implementations?  The current one was based
> > on a linux implementation.  A C version of these functions has likely
> > been written before, possibly even in newlib.  Were those considered?
> >
> > cgf
> 
> Sure, I have looked up standard-implementation of
> stricmp/strnicmp/strchr as code-base.  We could of course simply use
> C-runtime-funktions here, but well, those wouldn't be inlined.  The
> latter seems to me the only cause why string.h implements them at all.
> They are defined there as 'static inline', which makes them pure
> inlines.

Right, that's what I forgot entirely in my reply.  From my POV they
are good to go.  Chris?


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat


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