x86-64: Use -mtune=generic for generic kernels

The upcomming gcc 4.2 got a new option -mtune=generic to tune
code for both common AMD and Intel CPUs. Use this option
when available for generic kernels.

On x86-64 it is used with CONFIG_GENERIC_CPU. On i386 it is 
enabled with CONFIG_X86_GENERIC.  It won't affect the base
line CPU support in any ways and also not the minimum supported CPU.


Signed-off-by: Andi Kleen <ak@suse.de>

 arch/i386/Makefile.cpu |    4 ++++
 arch/x86_64/Makefile   |    1 +
 2 files changed, 5 insertions(+)

Index: linux/arch/i386/Makefile.cpu
===================================================================
--- linux.orig/arch/i386/Makefile.cpu
+++ linux/arch/i386/Makefile.cpu
@@ -39,3 +39,7 @@ cflags-$(CONFIG_X86_ELAN)	+= -march=i486
 # Geode GX1 support
 cflags-$(CONFIG_MGEODEGX1)	+= -march=pentium-mmx
 
+# add at the end to overwrite eventual tuning options from earlier
+# cpu entries
+cflags-$(CONFIG_X86_GENERIC) 	+= $(call tune,generic)
+
Index: linux/arch/x86_64/Makefile
===================================================================
--- linux.orig/arch/x86_64/Makefile
+++ linux/arch/x86_64/Makefile
@@ -29,6 +29,7 @@ CHECKFLAGS      += -D__x86_64__ -m64
 
 cflags-$(CONFIG_MK8) += $(call cc-option,-march=k8)
 cflags-$(CONFIG_MPSC) += $(call cc-option,-march=nocona)
+cflags-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=generic)
 CFLAGS += $(cflags-y)
 
 CFLAGS += -m64