[POWERPC] add Kconfig option for optimizing for cell
Since the PPE on cell is an in-order core, it suffers significantly
from wrong instruction scheduling. This adds a Kconfig option that
enables passing -mtune=cell to gcc in order to generate object
code that runs well on cell.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 86eb4cf..4c315be 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -71,6 +71,18 @@
depends on PPC64
def_bool y
+config TUNE_CELL
+ bool "Optimize for Cell Broadband Engine"
+ depends on PPC64
+ help
+ Cause the compiler to optimize for the PPE of the Cell Broadband
+ Engine. This will make the code run considerably faster on Cell
+ but somewhat slower on other machines. This option only changes
+ the scheduling of instructions, not the selection of instructions
+ itself, so the resulting kernel will keep running on all other
+ machines. When building a kernel that is supposed to run only
+ on Cell, you should also select the POWER4_ONLY option.
+
config 6xx
bool