u-boot/Kbuild
Marek Behún c1094987d1 build: support building with Link Time Optimizations
Add plumbing for building U-Boot with Link Time Optimizations.

When building with LTO, $(PLATFORM_LIBS) has to be in --whole-archive /
--no-whole-archive group, otherwise some functions declared in assembly
may not be resolved and linking may fail.

Note: clang may throw away linker list symbols it thinks are unused when
compiling with LTO. To force these symbols to be included, we refer to
them via the __ADDRESSABLE macro in a C file generated from compiled
built-in.o files before linking.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Simon Glass <sjg@chromium.org>
2021-05-24 14:21:30 -04:00

31 lines
783 B
Makefile

# SPDX-License-Identifier: GPL-2.0
#
# Kbuild for top-level directory of U-Boot
#####
# Generate generic-asm-offsets.h
generic-offsets-file := include/generated/generic-asm-offsets.h
always := $(generic-offsets-file)
targets := lib/asm-offsets.s
CFLAGS_REMOVE_asm-offsets.o := $(LTO_CFLAGS)
$(obj)/$(generic-offsets-file): $(obj)/lib/asm-offsets.s FORCE
$(call filechk,offsets,__GENERIC_ASM_OFFSETS_H__)
#####
# Generate asm-offsets.h
ifneq ($(wildcard $(srctree)/arch/$(ARCH)/lib/asm-offsets.c),)
offsets-file := include/generated/asm-offsets.h
endif
always += $(offsets-file)
targets += arch/$(ARCH)/lib/asm-offsets.s
CFLAGS_asm-offsets.o := -DDO_DEPS_ONLY
$(obj)/$(offsets-file): $(obj)/arch/$(ARCH)/lib/asm-offsets.s FORCE
$(call filechk,offsets,__ASM_OFFSETS_H__)