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

[Christopher Faylor <cgf-use-the-mailinglist-please at cygwin dot com>]

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