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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
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

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

2
init/Kconfig
View file

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