ARC: build: allow users to specify -mcpu
kernel build system used to add -mcpu for each ARC ISA as default.
These days there are versions and varaints of ARC HS cores some of which
have specific -mcpu options to fine tune / optimize generated code.
So allow users/external build systems to specify their own -mcpu
This will be used in future patches for HSDK-4xD board support which
uses specific -mcpu to utilize dual issue scheduling of the core.
Signed-off-by: Eugeniy Paltsev <[email protected]>
Signed-off-by: Vineet Gupta <[email protected]>
[abrodkin/vgupta: rewrote changelog]
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index fddc700..3230141 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -170,6 +170,15 @@
endchoice
+config ARC_TUNE_MCPU
+ string "Override default -mcpu compiler flag"
+ default ""
+ help
+ Override default -mcpu=xxx compiler flag (which is set depending on
+ the ISA version) with the specified value.
+ NOTE: If specified flag isn't supported by current compiler the
+ ISA default value will be used as a fallback.
+
config CPU_BIG_ENDIAN
bool "Enable Big Endian Mode"
help
diff --git a/arch/arc/Makefile b/arch/arc/Makefile
index 20e9ab6c..2b66e82 100644
--- a/arch/arc/Makefile
+++ b/arch/arc/Makefile
@@ -10,8 +10,25 @@
endif
cflags-y += -fno-common -pipe -fno-builtin -mmedium-calls -D__linux__
-cflags-$(CONFIG_ISA_ARCOMPACT) += -mA7
-cflags-$(CONFIG_ISA_ARCV2) += -mcpu=hs38
+
+tune-mcpu-def-$(CONFIG_ISA_ARCOMPACT) := -mA7
+tune-mcpu-def-$(CONFIG_ISA_ARCV2) := -mcpu=hs38
+
+ifeq ($(CONFIG_ARC_TUNE_MCPU),"")
+cflags-y += $(tune-mcpu-def-y)
+else
+tune-mcpu := $(shell echo $(CONFIG_ARC_TUNE_MCPU))
+tune-mcpu-ok := $(call cc-option-yn, $(tune-mcpu))
+ifeq ($(tune-mcpu-ok),y)
+cflags-y += $(tune-mcpu)
+else
+# The flag provided by 'CONFIG_ARC_TUNE_MCPU' option isn't known by this compiler
+# (probably the compiler is too old). Use ISA default mcpu flag instead as a safe option.
+$(warning ** WARNING ** CONFIG_ARC_TUNE_MCPU flag '$(tune-mcpu)' is unknown, fallback to '$(tune-mcpu-def-y)')
+cflags-y += $(tune-mcpu-def-y)
+endif
+endif
+
ifdef CONFIG_ARC_CURR_IN_REG
# For a global register defintion, make sure it gets passed to every file
