On Sun, Mar 7, 2021 at 12:26 PM Marek Behún <marek.be...@nic.cz> wrote: > > 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. > > On the other hand, by using thin archives we can make (via the > --whole-archive use flag) the final linking behave as if we passed all > the object files from the archives to the linking program as arguments. > > We also need to use the P flag for ar, otherwise final linking may fail. > > Signed-off-by: Marek Behún <marek.be...@nic.cz> > --- > 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 7b0ba9df9a..6dc47810ea 100644 > --- a/Makefile > +++ b/Makefile > @@ -1754,9 +1754,9 @@ 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 > \ > + --start-group --whole-archive > \
--start-group is useless now. > $(u-boot-main) > \ > - --end-group > \ > + --no-whole-archive --end-group > \ and --end-group > $(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..d11b9c63c9 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,--start-group -Wl,--whole-archive \ > + $(u-boot-main) \ > + -Wl,--no-whole-archive -Wl,--end-group \ > $(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,--start-group -Wl,--whole-archive \ > + $(patsubst $(obj)/%,%,$(u-boot-spl-main)) \ > + $(patsubst $(obj)/%,%,$(u-boot-spl-platdata)) \ > + -Wl,--no-whole-archive -Wl,--end-group \ > $(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..a9a02d7d33 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 $@; $(AR) cPrsT$(KBUILD_ARFLAGS) $@) nits: should we use D for the empty one for consistency? > > $(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 $@; $(AR) cPrs$(KBUILD_ARFLAGS) $@ $(lib-y) It looks this line change is not needed > > $(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 $@ $(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 3b5f5046c9..889debb93c 100644 > --- a/scripts/Makefile.spl > +++ b/scripts/Makefile.spl > @@ -423,10 +423,10 @@ quiet_cmd_u-boot-spl ?= LD $@ > cmd_u-boot-spl ?= (cd $(obj) && \ > $(LD) $(KBUILD_LDFLAGS) $(LDFLAGS_$(@F)) \ > $(patsubst $(obj)/%,%,$(u-boot-spl-init)) \ > - --start-group \ > + --start-group --whole-archive \ > $(patsubst $(obj)/%,%,$(u-boot-spl-main)) \ > $(patsubst $(obj)/%,%,$(u-boot-spl-platdata)) \ > - --end-group \ > + --no-whole-archive --end-group \ > $(PLATFORM_LIBS) -Map $(SPL_BIN).map -o $(SPL_BIN) \ > ) > Otherwise LGTM: Reviewed-by: Bin Meng <bmeng...@gmail.com> Regards, Bin
