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To vypadá jako nastavení gcc ... v gentoo mam v make.conf u C2D CFLAGS="-march=nocona -O2 -pipe -fomit-frame-pointer", nevim, co máš za procesor, co bys tam měl dát. Tip máš ... podle man:gcc ...

-mtune=cpu-type
 Tune to cpu-type everything applicable about the generated code, except for the ABI and the set of available instructions. The choices for cpu-type are: 
generic
 Produce code optimized for the most common IA32/AMD64/EM64T processors. If you know the CPU on which your code will run, 
then you should use the corresponding -mtune option instead of -mtune=generic. But, if you do not know exactly what CPU users 
of your application will have, then you should use this option. 

 As new processors are deployed in the marketplace, the behavior of this option will change. Therefore, if you upgrade to 
a newer version of GCC, the code generated option will change to reflect the processors that were most common when that version of GCC was released. 

 There is no -march=generic option because -march indicates the instruction set the compiler can use, and there is no generic 
instruction set applicable to all processors. In contrast, -mtune indicates the processor (or, in this case, collection of processors) 
for which the code is optimized. 
native
 This selects the CPU to tune for at compilation time by determining the processor type of the compiling machine. 
Using -mtune=native will produce code optimized for the local machine under the constraints of the selected 
instruction set. Using -march=native will enable all instruction subsets supported by the local machine (hence 
the result might not run on different machines). 
i386
 Original Intel's i386 CPU. 
i486
 Intel's i486 CPU. (No scheduling is implemented for this chip.) 
i586, pentium
 Intel Pentium CPU with no MMX support. 
pentium-mmx
 Intel PentiumMMX CPU based on Pentium core with MMX instruction set support. 
pentiumpro
 Intel PentiumPro CPU. 
i686
 Same as generic, but when used as march option, PentiumPro instruction set will be used, so the code will run on all i686 family chips. 
pentium2
 Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support. 
pentium3, pentium3m
 Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set support. 
pentium-m
 Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set support. Used by Centrino notebooks. 
pentium4, pentium4m
 Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support. 
prescott
 Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction set support. 
nocona
 Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE, SSE2 and SSE3 instruction set support. 
core2
 Intel Core2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 instruction set support. 
k6
AMD K6 CPU with MMX instruction set support. 
k6-2, k6-3
 Improved versions of AMD K6 CPU with MMX and 3dNOW! instruction set support. 
athlon, athlon-tbird
AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and SSE prefetch instructions support. 
athlon-4, athlon-xp, athlon-mp
 Improved AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and full SSE instruction set support. 
k8, opteron, athlon64, athlon-fx
AMD K8 core based CPUs with x86-64 instruction set support. (This supersets MMX, SSE, SSE2, 3dNOW!, enhanced 3dNOW! and 64-bit instruction set extensions.) 
k8-sse3, opteron-sse3, athlon64-sse3
 Improved versions of k8, opteron and athlon64 with SSE3 instruction set support. 
amdfam10, barcelona
AMD Family 10h core based CPUs with x86-64 instruction set support. (This supersets MMX, SSE, SSE2, SSE3, SSE4A, 3dNOW!, enhanced 3dNOW!, ABM and 64-bit instruction set extensions.) 
winchip-c6
IDT Winchip C6 CPU, dealt in same way as i486 with additional MMX instruction set support. 
winchip2
IDT Winchip2 CPU, dealt in same way as i486 with additional MMX and 3dNOW! instruction set support. 
c3
 Via C3 CPU with MMX and 3dNOW! instruction set support. (No scheduling is implemented for this chip.) 
c3-2
 Via C3-2 CPU with MMX and SSE instruction set support. (No scheduling is implemented for this chip.) 
geode
 Embedded AMD CPU with MMX and 3dNOW! instruction set support. 


 While picking a specific cpu-type will schedule things appropriately for that particular chip, 
the compiler will not generate any code that does not run on the i386 without the -march=cpu-type option being used.