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openrisc: Add gcc machine instruction flag configuration 

OpenRISC GCC supports flags to enable the backend to output instructions
if they are supported by a target processor.  This patch adds
configuration flags to enable configuring these flags to tune the kernel
for a particular CPU configuration.

In the future we could also enable all of these flags by default and
provide instruction emulation in the kernel to make these choices easier
for users but this is what we provide for now.

Signed-off-by: Stafford Horne <shorne@gmail.com>
This commit is contained in:
Stafford Horne 2022-01-22 13:32:38 +09:00
parent 635267b7a8
commit 87e387acd8
2 changed files with 70 additions and 0 deletions
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53
arch/openrisc/Kconfig
View File

@ -114,6 +114,59 @@ config OPENRISC_HAVE_INST_DIV
default y
help
Select this if your implementation has a hardware divide instruction
config OPENRISC_HAVE_INST_CMOV
bool "Have instruction l.cmov for conditional move"
default n
help
This config enables gcc to generate l.cmov instructions when compiling
the kernel which in general will improve performance and reduce the
binary size.
Select this if your implementation has support for the Class II
l.cmov conistional move instruction.
Say N if you are unsure.
config OPENRISC_HAVE_INST_ROR
bool "Have instruction l.ror for rotate right"
default n
help
This config enables gcc to generate l.ror instructions when compiling
the kernel which in general will improve performance and reduce the
binary size.
Select this if your implementation has support for the Class II
l.ror rotate right instruction.
Say N if you are unsure.
config OPENRISC_HAVE_INST_RORI
bool "Have instruction l.rori for rotate right with immediate"
default n
help
This config enables gcc to generate l.rori instructions when compiling
the kernel which in general will improve performance and reduce the
binary size.
Select this if your implementation has support for the Class II
l.rori rotate right with immediate instruction.
Say N if you are unsure.
config OPENRISC_HAVE_INST_SEXT
bool "Have instructions l.ext* for sign extension"
default n
help
This config enables gcc to generate l.ext* instructions when compiling
the kernel which in general will improve performance and reduce the
binary size.
Select this if your implementation has support for the Class II
l.exths, l.extbs, l.exthz and l.extbz size extend instructions.
Say N if you are unsure.
endmenu
config NR_CPUS

17
arch/openrisc/Makefile
View File

@ -21,6 +21,7 @@ OBJCOPYFLAGS := -O binary -R .note -R .comment -S
LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
KBUILD_CFLAGS += -pipe -ffixed-r10 -D__linux__
KBUILD_CFLAGS += -msfimm -mshftimm
all: vmlinux.bin
@ -38,6 +39,22 @@ else
KBUILD_CFLAGS += $(call cc-option,-msoft-div)
endif
ifeq ($(CONFIG_OPENRISC_HAVE_INST_CMOV),y)
KBUILD_CFLAGS += $(call cc-option,-mcmov)
endif
ifeq ($(CONFIG_OPENRISC_HAVE_INST_ROR),y)
KBUILD_CFLAGS += $(call cc-option,-mror)
endif
ifeq ($(CONFIG_OPENRISC_HAVE_INST_RORI),y)
KBUILD_CFLAGS += $(call cc-option,-mrori)
endif
ifeq ($(CONFIG_OPENRISC_HAVE_INST_SEXT),y)
KBUILD_CFLAGS += $(call cc-option,-msext)
endif
head-y := arch/openrisc/kernel/head.o
libs-y += $(LIBGCC)