[patch cygwin]: Replace inline-assembler in string.h by C implementation
Christopher Faylor
cgf-use-the-mailinglist-please@cygwin.com
Wed Oct 24 15:42:00 GMT 2012
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
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