From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?q?Marek=20Beh=C3=BAn?= Date: Thu, 20 May 2021 13:24:02 +0200 Subject: [PATCH u-boot v4 13/36] build: use thin archives instead of incremental linking In-Reply-To: <20210520112425.25166-1-marek.behun@nic.cz> References: <20210520112425.25166-1-marek.behun@nic.cz> Message-ID: <20210520112425.25166-14-marek.behun@nic.cz> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Currently we use incremental linking (ld -r) to link several object files from one directory into one built-in.o object file containing the linked code from that directory (and its subdirectories). Linux has, some time ago, moved to thin archives instead. Thin archives are archives (.a) that do not really contain the object files, only references to them. Using thin archives instead of incremental linking - saves disk space - apparently works better with dead code elimination - makes things easier for LTO The third point is the important one for us. With incremental linking there are several options how to do LTO, and that would unnecessarily complicate things. We have to use the --whole-archive/--no-whole-archive linking option instead of --start-group/--end-group, otherwise linking may fail because of unresolved symbols, or the resulting binary will be unusable. We also need to use the P flag for ar, otherwise final linking may fail. Signed-off-by: Marek Beh?n --- Makefile | 4 ++-- arch/sandbox/config.mk | 10 +++++++--- scripts/Makefile.build | 16 ++++++++-------- scripts/Makefile.spl | 4 ++-- 4 files changed, 19 insertions(+), 15 deletions(-) diff --git a/Makefile b/Makefile index bfdb65e098..70728b3351 100644 --- a/Makefile +++ b/Makefile @@ -1711,9 +1711,9 @@ ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(ARCH)/Makefile.postlink) quiet_cmd_u-boot__ ?= LD $@ cmd_u-boot__ ?= $(LD) $(KBUILD_LDFLAGS) $(LDFLAGS_u-boot) -o $@ \ -T u-boot.lds $(u-boot-init) \ - --start-group \ + --whole-archive \ $(u-boot-main) \ - --end-group \ + --no-whole-archive \ $(PLATFORM_LIBS) -Map u-boot.map; \ $(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true) diff --git a/arch/sandbox/config.mk b/arch/sandbox/config.mk index 189e9c2b0c..2149771324 100644 --- a/arch/sandbox/config.mk +++ b/arch/sandbox/config.mk @@ -17,13 +17,17 @@ PLATFORM_CPPFLAGS += $(shell $(SDL_CONFIG) --cflags) endif cmd_u-boot__ = $(CC) -o $@ -Wl,-T u-boot.lds $(u-boot-init) \ - -Wl,--start-group $(u-boot-main) -Wl,--end-group \ + -Wl,--whole-archive \ + $(u-boot-main) \ + -Wl,--no-whole-archive \ $(PLATFORM_LIBS) -Wl,-Map -Wl,u-boot.map cmd_u-boot-spl = (cd $(obj) && $(CC) -o $(SPL_BIN) -Wl,-T u-boot-spl.lds \ $(patsubst $(obj)/%,%,$(u-boot-spl-init)) \ - -Wl,--start-group $(patsubst $(obj)/%,%,$(u-boot-spl-main)) \ - $(patsubst $(obj)/%,%,$(u-boot-spl-platdata)) -Wl,--end-group \ + -Wl,--whole-archive \ + $(patsubst $(obj)/%,%,$(u-boot-spl-main)) \ + $(patsubst $(obj)/%,%,$(u-boot-spl-platdata)) \ + -Wl,--no-whole-archive \ $(PLATFORM_LIBS) -Wl,-Map -Wl,u-boot-spl.map -Wl,--gc-sections) CONFIG_ARCH_DEVICE_TREE := sandbox diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 705a886cb9..7e59ca54cd 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -331,12 +331,11 @@ $(sort $(subdir-obj-y)): $(subdir-ym) ; # Rule to compile a set of .o files into one .o file # ifdef builtin-target -quiet_cmd_link_o_target = LD $@ +quiet_cmd_link_o_target = AR $@ # If the list of objects to link is empty, just create an empty built-in.o cmd_link_o_target = $(if $(strip $(obj-y)),\ - $(LD) $(ld_flags) -r -o $@ $(filter $(obj-y), $^) \ - $(cmd_secanalysis),\ - rm -f $@; $(AR) rcs$(KBUILD_ARFLAGS) $@) + rm -f $@; $(AR) cDPrsT $@ $(filter $(obj-y), $^), \ + rm -f $@; $(AR) cDPrsT$(KBUILD_ARFLAGS) $@) $(builtin-target): $(obj-y) FORCE $(call if_changed,link_o_target) @@ -362,7 +361,7 @@ $(modorder-target): $(subdir-ym) FORCE # ifdef lib-target quiet_cmd_link_l_target = AR $@ -cmd_link_l_target = rm -f $@; $(AR) rcs$(KBUILD_ARFLAGS) $@ $(lib-y) +cmd_link_l_target = rm -f $@; $(AR) cDPrsT$(KBUILD_ARFLAGS) $@ $(lib-y) $(lib-target): $(lib-y) FORCE $(call if_changed,link_l_target) @@ -382,10 +381,11 @@ $(filter $(addprefix $(obj)/, \ $($(subst $(obj)/,,$(@:.o=-objs))) \ $($(subst $(obj)/,,$(@:.o=-y)))), $^) -quiet_cmd_link_multi-y = LD $@ -cmd_link_multi-y = $(LD) $(ld_flags) -r -o $@ $(link_multi_deps) $(cmd_secanalysis) -quiet_cmd_link_multi-m = LD [M] $@ +quiet_cmd_link_multi-y = AR $@ +cmd_link_multi-y = rm -f $@; $(AR) cDPrsT$(KBUILD_ARFLAGS) $@ $(link_multi_deps) + +quiet_cmd_link_multi-m = AR [M] $@ cmd_link_multi-m = $(cmd_link_multi-y) $(multi-used-y): FORCE diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl index 92775fef54..ac2d2033ba 100644 --- a/scripts/Makefile.spl +++ b/scripts/Makefile.spl @@ -456,10 +456,10 @@ quiet_cmd_u-boot-spl ?= LD $@ cd $(obj) && \ $(LD) $(KBUILD_LDFLAGS) $(LDFLAGS_$(@F)) \ $(patsubst $(obj)/%,%,$(u-boot-spl-init)) \ - --start-group \ + --whole-archive \ $(patsubst $(obj)/%,%,$(u-boot-spl-main)) \ $(patsubst $(obj)/%,%,$(u-boot-spl-platdata)) \ - --end-group \ + --no-whole-archive \ $(PLATFORM_LIBS) -Map $(SPL_BIN).map -o $(SPL_BIN) \ ) -- 2.26.3