Since the PPE on cell is an in-order core, it suffers significantly
from wrong instruction scheduling. This adds an 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 <[EMAIL PROTECTED]>
---
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 6015a92..87aff53 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -92,6 +92,10 @@ else
endif
endif
+ifeq ($(CONFIG_TUNE_CELL),y)
+ CFLAGS += $(call cc-option,-mtune=cell)
+endif
+
# No AltiVec instruction when building kernel
CFLAGS += $(call cc-option,-mno-altivec)
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 @@ config POWER4
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
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