diff options
| -rw-r--r-- | Makefile | 17 | ||||
| -rw-r--r-- | arch/arm/config.mk | 4 | ||||
| -rw-r--r-- | arch/arm/include/asm/global_data.h | 2 | ||||
| -rw-r--r-- | doc/build/gcc.rst | 17 | ||||
| -rw-r--r-- | scripts/Makefile.spl | 2 |
5 files changed, 33 insertions, 9 deletions
@@ -643,6 +643,13 @@ export CFLAGS_EFI # Compiler flags to add when building EFI app export CFLAGS_NON_EFI # Compiler flags to remove when building EFI app export EFI_TARGET # binutils target if EFI is natively supported +export LTO_ENABLE + +# This is y if LTO is enabled for this build. See NO_LTO=1 to disable LTO +ifeq ($(NO_LTO),) +LTO_ENABLE=$(if $(CONFIG_LTO),y) +endif + # If board code explicitly specified LDSCRIPT or CONFIG_SYS_LDSCRIPT, use # that (or fail if absent). Otherwise, search for a linker script in a # standard location. @@ -708,16 +715,16 @@ endif LTO_CFLAGS := LTO_FINAL_LDFLAGS := export LTO_CFLAGS LTO_FINAL_LDFLAGS -ifdef CONFIG_LTO +ifeq ($(LTO_ENABLE),y) ifeq ($(cc-name),clang) - LTO_CFLAGS += -flto + LTO_CFLAGS += -DLTO_ENABLE -flto LTO_FINAL_LDFLAGS += -flto AR = $(shell $(CC) -print-prog-name=llvm-ar) NM = $(shell $(CC) -print-prog-name=llvm-nm) else NPROC := $(shell nproc 2>/dev/null || echo 1) - LTO_CFLAGS += -flto=$(NPROC) + LTO_CFLAGS += -DLTO_ENABLE -flto=$(NPROC) LTO_FINAL_LDFLAGS += -fuse-linker-plugin -flto=$(NPROC) # use plugin aware tools @@ -1765,7 +1772,7 @@ ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(ARCH)/Makefile.postlink) # Generate linker list symbols references to force compiler to not optimize # them away when compiling with LTO -ifdef CONFIG_LTO +ifeq ($(LTO_ENABLE),y) u-boot-keep-syms-lto := keep-syms-lto.o u-boot-keep-syms-lto_c := $(patsubst %.o,%.c,$(u-boot-keep-syms-lto)) @@ -1787,7 +1794,7 @@ endif # Rule to link u-boot # May be overridden by arch/$(ARCH)/config.mk -ifdef CONFIG_LTO +ifeq ($(LTO_ENABLE),y) quiet_cmd_u-boot__ ?= LTO $@ cmd_u-boot__ ?= \ $(CC) -nostdlib -nostartfiles \ diff --git a/arch/arm/config.mk b/arch/arm/config.mk index b3548ce243..2065438d05 100644 --- a/arch/arm/config.mk +++ b/arch/arm/config.mk @@ -15,11 +15,11 @@ CFLAGS_NON_EFI := -fno-pic -ffixed-r9 -ffunction-sections -fdata-sections \ -fstack-protector-strong CFLAGS_EFI := -fpic -fshort-wchar -ifneq ($(CONFIG_LTO)$(CONFIG_USE_PRIVATE_LIBGCC),yy) +ifneq ($(LTO_ENABLE)$(CONFIG_USE_PRIVATE_LIBGCC),yy) LDFLAGS_FINAL += --gc-sections endif -ifndef CONFIG_LTO +ifneq ($(LTO_ENABLE),y) PLATFORM_RELFLAGS += -ffunction-sections -fdata-sections endif diff --git a/arch/arm/include/asm/global_data.h b/arch/arm/include/asm/global_data.h index 6ee2a76761..cd6112dfcd 100644 --- a/arch/arm/include/asm/global_data.h +++ b/arch/arm/include/asm/global_data.h @@ -101,7 +101,7 @@ struct arch_global_data { #include <asm-generic/global_data.h> -#if defined(__clang__) || defined(CONFIG_LTO) +#if defined(__clang__) || defined(LTO_ENABLE) #define DECLARE_GLOBAL_DATA_PTR #define gd get_gd() diff --git a/doc/build/gcc.rst b/doc/build/gcc.rst index ee544ad87e..a71f860a48 100644 --- a/doc/build/gcc.rst +++ b/doc/build/gcc.rst @@ -152,6 +152,23 @@ of dtc is new enough. It also makes sure that pylibfdt is present, if needed Note that the :doc:`tools` are always built with the included version of libfdt so it is not possible to build U-Boot tools with a system libfdt, at present. +Link-time optimisation (LTO) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +U-Boot supports link-time optimisation which can reduce the size of the final +U-Boot binaries, particularly with SPL. + +At present this can be enabled by ARM boards by adding `CONFIG_LTO=y` into the +defconfig file. Other architectures are not supported. LTO is enabled by default +for sandbox. + +This does incur a link-time penalty of several seconds. For faster incremental +builds during development, you can disable it by setting `NO_LTO` to `1`. + +.. code-block:: bash + + NO_LTO=1 make + Other build targets ~~~~~~~~~~~~~~~~~~~ diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl index 3bafeb4fe9..0b3a51da13 100644 --- a/scripts/Makefile.spl +++ b/scripts/Makefile.spl @@ -489,7 +489,7 @@ endif # Rule to link u-boot-spl # May be overridden by arch/$(ARCH)/config.mk -ifdef CONFIG_LTO +ifeq ($(LTO_ENABLE),y) quiet_cmd_u-boot-spl ?= LTO $@ cmd_u-boot-spl ?= \ ( \ |