On Tue, Aug 27, 2002 at 08:57:23PM +0200, Markus Hahn wrote:
> Hi Liste,
> was bewirkten eigentlich die gcc optionen CFLAGS bzw CXXFLAGS?
Garnichts. Diese Variablen werden als Konvention (und in den
Standardregeln) von make verwendet, um dort Optionen an den C- bzw
C++-Kompiler zu reichen.
> optimiere ich mit " -march=i486 -mcpu=i686" mein neues Programm
> oder beschleunige ich damit nur die Complierung??
Aus dem GCC-Handbuch:
These `-m' options are defined for the i386 family of computers:
-mcpu=cpu-type
Assume the defaults for the machine type cpu-type when
scheduling instructions. The choices for cpu-type are
`i386', `i486', `i586', `i686', `pentium', `pentiumpro',
`k6', and `athlon'
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. `i586' is
equivalent to `pentium' and `i686' is equivalent to
`pentiumpro'. `k6' is the AMD chip as opposed to the Intel
ones.
-march=cpu-type
Generate instructions for the machine type cpu-type. The
choices for cpu-type are the same as for `-mcpu'.
Moreover, specifying `-march=cpu-type' implies
`-mcpu=cpu-type'.
D.h., Deine Programm laufen evtl. nicht mehr auf einem i386, und sind
auf einen i686 m�glicherweise schneller. Mit der Laufzeit des
Kompilers hat das i.d.R. wenig zu tun.
Jochen
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