Re: epan/asm_utils* and NASM

[Guy Harris <guy () alum mit edu>]

On Oct 16, 2017, at 3:05 AM, Graham Bloice <graham.bloice () trihedral com> wrote:

> On 13 October 2017 at 21:50, Gerald Combs <gerald () wireshark org> wrote:
>
> > Before we migrated away from NMake, epan/Makefile.nmake built the assembly versions of various routines for x86 (but 
> > not x64) defined in epan/asm_utils_win32_x86.asm. Should we resurrect it in epan/CMakeLists.txt or get rid of it 
> > along with the NASM download in tools/win-setup.ps1?
>
> I was vaguely under the impression that compiler intrinsics were the way forward for these kind of things

Compiler intrinsics are the way to do things for which there are compiler intrinsics.  Unless by "compiler intrinsics" 
you're referring to "inline asms" of the sort that GCC provides, I'm not sure there are compiler intrinsics for most of 
the operations for which we're providing assembler-language implementations.  (The one exception is strcmp() and the 
like, which GCC, and possibly other compilers, often turn into inline code, and for which there are often optimized 
implementations, at least on some platforms, because it's part of C.)

> However, I don't see much point in attempting to optimise things without measuring what we're trying to optimise, 
> i.e. we need some form of benchmark.

Tomas did some profiling back in

        https://www.wireshark.org/lists/wireshark-dev/200711/msg00303.html

and in

        https://www.wireshark.org/lists/wireshark-dev/200711/msg00068.html

said

        I was able (with about 80 lines in assembler) to reduce time spent in libwireshark.dll during startup from cca 
2600ms to 1300ms on my PC.

so that removed about 1.3 seconds of startup time.
___________________________________________________________________________
Sent via:    Wireshark-dev mailing list <wireshark-dev () wireshark org>
Archives:    https://www.wireshark.org/lists/wireshark-dev
Unsubscribe: https://www.wireshark.org/mailman/options/wireshark-dev
             mailto:wireshark-dev-request () wireshark org?subject=unsubscribe