arch/Config.in.x86: drop BR2_x86_generic
The fuzzy generic x86 variant doesn't make much sense in the context of
Buildroot, and the recent change to use -march instead of -mtune broke it.
From the GCC manual:
https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/i386-and-x86-64-Options.html#i386-and-x86-64-Options:
-mtune=cpu-type
Tune to cpu-type everything applicable about the generated code,
except for the ABI and the set of available instructions. While
picking a specific cpu-type schedules things appropriately for that
particular chip, the compiler does not generate any code that cannot
run on the default machine type unless you use a -march=cpu-type
option. For example, if GCC is configured for i686-pc-linux-gnu then
-mtune=pentium4 generates code that is tuned for Pentium 4 but still
runs on i686 machines.
The choices for cpu-type are the same as for -march. In addition,
-mtune supports 2 extra choices for cpu-type:
‘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 or -march 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, code generation controlled by this option will
change to reflect the processors that are most common at the
time that version of GCC is 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.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
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