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kbuild: test dead code/data elimination support in Kconfig

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This config option should be enabled only when both the compiler and
the linker support necessary flags.  Add proper dependencies to Kconfig.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This commit is contained in:
Masahiro Yamada 2018-08-22 22:51:09 +09:00
parent f6f57a4643
commit e85d1d65cd
2 changed files with 4 additions and 6 deletions
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8
Makefile
View file

@ -790,8 +790,8 @@ KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
KBUILD_CFLAGS_KERNEL += $(call cc-option,-ffunction-sections,)
KBUILD_CFLAGS_KERNEL += $(call cc-option,-fdata-sections,)
KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
LDFLAGS_vmlinux += --gc-sections
endif
# arch Makefile may override CC so keep this after arch Makefile is included
@ -857,10 +857,6 @@ LDFLAGS_BUILD_ID := $(call ld-option, --build-id)
KBUILD_LDFLAGS_MODULE += $(LDFLAGS_BUILD_ID)
LDFLAGS_vmlinux += $(LDFLAGS_BUILD_ID)
ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
LDFLAGS_vmlinux += $(call ld-option, --gc-sections,)
endif
ifeq ($(CONFIG_STRIP_ASM_SYMS),y)
LDFLAGS_vmlinux += $(call ld-option, -X,)
endif

2
init/Kconfig
View file

@ -1085,6 +1085,8 @@ config LD_DEAD_CODE_DATA_ELIMINATION
bool "Dead code and data elimination (EXPERIMENTAL)"
depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
depends on EXPERT
depends on $(cc-option,-ffunction-sections -fdata-sections)
depends on $(ld-option,--gc-sections)
help
Enable this if you want to do dead code and data elimination with
the linker by compiling with -ffunction-sections -fdata-sections,