From: "M. Edward (Ed) Borasky" <znmeb@...>
Date: 2009-02-02T14:32:54+09:00
Subject: Re: Minor 1.8 <-> 1.9 performance comparison gotcha

M. Edward (Ed) Borasky wrote:
>> gcc --version
>>     
> gcc (SUSE Linux) 4.3.2 [gcc-4_3-branch revision 141291]
>
>
>   
OK ... here's the manual page for x86 and x86_64:

http://gcc.gnu.org/onlinedocs/gcc-4.3.3/gcc/i386-and-x86_002d64-Options.html#i386-and-x86_002d64-Options

Essentially, if you're compiling and always running on the same system,
the magic code is "-march=native". For older versions of GCC that don't
have "native", use "-march=<whatever>".

The difference between "-march" and "-mtune" is documented there as
well. Basically, "-march" code is guaranteed to run only on the specific
architecture variant called out in the flag.

-- 
M. Edward (Ed) Borasky

I've never met a happy clam. In fact, most of them were pretty steamed.