diff options
| author | Simon Glass <sjg@chromium.org> | 2022-08-03 12:13:08 -0600 |
|---|---|---|
| committer | Tom Rini <trini@konsulko.com> | 2022-09-02 16:20:11 -0400 |
| commit | a55014d09b29d7bc2cbaeb8e41a155c9a257a183 (patch) | |
| tree | 7651a422b0d01a6a8ed0375e8f1a6eff3065df3f /Makefile | |
| parent | 583f1b2f10be36f86a2da3686d406bfd90cfbc70 (diff) | |
Makefile: Allow LTO to be disabled for a build
LTO (Link-Time Optimisation) is an very useful feature which can
significantly reduce the size of U-Boot binaries. So far it has been
made available for selected ARM boards and sandbox.
However, incremental builds are much slower when LTO is used. For example,
an incremental build of sandbox takes 2.1 seconds on my machine, but 6.7
seconds with LTO enabled.
Add a NO_LTO parameter to the build, similar to NO_SDL, so it can be
disabled during development if needed, for faster builds.
Add some documentation about LTO while we are here.
Signed-off-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'Makefile')
| -rw-r--r-- | Makefile | 17 |
1 files changed, 12 insertions, 5 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 \ |