Wireshark-dev: Re: [Wireshark-dev] How to define HAVE_SSE42 with autotools?
From: Anders Broman <[email protected]>
Date: Tue, 10 Jun 2014 17:06:24 +0000
-----Original Message-----
>From: [email protected] [mailto:[email protected]] On Behalf Of Guy Harris
>Sent: den 10 juni 2014 18:32
>To: Developer support list for Wireshark
>Subject: Re: [Wireshark-dev] How to define HAVE_SSE42 with autotools?
>HAVE_SSE42 is used in two places:
>	1) wsutil/ws_mempbrk_sse42.c, where it controls whether to build that file at all;
>	2) wsutil/ws_mempbrk.c, where it controls whether to check whether the CPU has SSE 4.2 and, if it does, call the SSE 4.2 version of the code.
>So what HAVE_SSE42 really seems to mean is "does the compiler support the intrinsics used in wsutil/ws_mempbrk_sse42.c?"
>Should we, instead, check for compiler support for those intrinsics?

Yes I guess...

>And will the compiler generate code for those intrinsics, using the SSE 4.2 instructions, even if you haven't told it, with a command-line option, to generate SSE 4.2 code in general?  Or does the >compiler not do a good job of supporting choosing whether to use SSE 4.2 instructions at run time rather than at compile time?

I have recently added some macros I found that define HAVE_SSE4_2 so at least the stuff compiles now on all the buildbots(I think).

I'm not sure if there should be a command line option or not. But ideally we should compile ws_mempbrk_sse42.c if the compiler supports it and check cpu_info() at runtime to use it or not.

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