Hi Laurent, It occurs to me that all we're after is to enable SSE functions such as _mm_set_epi32. We're not trying to have the binary optimized in any implicit way, it is all explicit. The problem seems to be that -msse4.2 will do both * activate _mm_set_epi32 etc functions * optimize the binary to use sse4.2 instructions Do you know of a compiler flag that would only * activate _mm_set_epi32 etc functions and not * optimize the binary to use sse4.2 instructions ? It may be a RTFM question and I apologize for that. Reading http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/i386-and-x86-64-Options.html#i386-and-x86-64-Options it looks like this is more or less what --mtune=corei7-avx would do (because gf-complete uses PCLMUL when available). But it feels weird to specify a specific processor model where what we need is a set of features. Thanks for your help :-) On 25/03/2014 10:43, Laurent GUERBY wrote: > On Mon, 2014-03-24 at 22:27 +0100, Loic Dachary wrote: >> >> On 23/03/2014 23:34, Laurent GUERBY wrote: >>> http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/i386-and-x86-64-Options.html#i386-and-x86-64-Options >>> >>> So unless you want to run your code a very very old x86 32 bit processor >>> "-msse" shouldn't be an issue. "-msse2" is similar. >> >> This is good to know :) Should I be worried about unintended side effects of -msse4.2 -mssse3 -msse4.1 or -mpclmul ? These are the flags that gf-complete are using, specifically. > > Hi, > > SSE4.2 will be available only in more recent > processors as documented on the page above. > > If your library already is dynamically checking for processor > feature I would advise to be conservative in your > -m flags, ie using what debian would use for maximum > x86 portability. > > Sincerely, > > Laurent > -- Loïc Dachary, Artisan Logiciel Libre
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