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Re: Cygwin 32bit: Can't use gcc -mfpmath=sse

On 9/11/2015 8:03 AM, HK wrote:
> On Fri, 11 Sep 2015 10:16:56 +0200, Evgeny Grin <> wrote:
>> 10.09.2015, 23:52, "HK" <>:
>>> On Thu, 10 Sep 2015 13:19:04 +0200, V?clav_Haisman wrote:
>>>>  On 10 September 2015 at 01:30, HK wrote:
>>>>>  hello.c:1:0: warning: SSE instruction set disabled, using 387
>>>>>  arithmetics
>>>>  Does it help to use `-march=native`? My hunch is that this is because
>>>>  the default CPU type is set to such that does not have SSE.
>>> Yep, that did the trick. Thanks for the suggestion. Now, is this a gcc
>>> build
>>> build problem? The 64bit version doesn't need -march=native and that
>>> is on
>>> the same computer.
>> It's not a problem as by default GCC generate code compatible with
>> maximum number of CPU models.
>> If you need to generate an SSE instructions, you have to use at lest
>> -march=pentium3.
>> For x86-64 version, SSE is always enabled as all x86-64 CPUs support
>> SSE and SSE2.
>> See
> Thanks. While I don't quite agree with the choice of defaults it makes
> sense.
> So does my 32bit window next to the 64bit window on the same computer
> really
> have a different instruction set? Anyway, case closed.
Intel compilers made SSE2 the default even for 32-bit mode, subsequent
to all CPUs which supported 387 but not SSE3 going out of production. 
There's still a lot of interest in 387 mode, however. 
You might argue for making SSE3 the default, but it's generally
important nowadays to set an appropriate option for the target platforms.

Tim Prince

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