[RFC PATCH u-boot 01/12] build: use thin archives instead of incremental linking

[Marek Behún]

Using thin archives instead of incremental linking
- saves disk space
- works better with dead code elimination
- prepares for potential LTO

Linux does this for some time now, do this also in U-Boot.

Signed-off-by: Marek Behún <marek.behun at nic.cz>
---
 Makefile               | 2 +-
 arch/sandbox/config.mk | 6 +++---
 scripts/Makefile.build | 5 ++---
 scripts/Makefile.spl   | 7 +++----
 4 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/Makefile b/Makefile
index 6cdd3677eb..33d0b80de8 100644
--- a/Makefile
+++ b/Makefile
@@ -1750,7 +1750,7 @@ 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 $(u-boot-main) --end-group                 \
+      --whole-archive $(u-boot-main) --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..ebbb094744 100644
--- a/arch/sandbox/config.mk
+++ b/arch/sandbox/config.mk
@@ -17,13 +17,13 @@ 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)) -Wl,--no-whole-archive \
+	-Wl,--start-group $(patsubst $(obj)/%,%,$(u-boot-spl-platdata)) -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..3659d0af1b 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -331,11 +331,10 @@ $(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) cDPrsT $@ $(filter $(obj-y), $^), \
 		      rm -f $@; $(AR) rcs$(KBUILD_ARFLAGS) $@)
 
 $(builtin-target): $(obj-y) FORCE
diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl
index ea4e045769..f9faf804de 100644
--- a/scripts/Makefile.spl
+++ b/scripts/Makefile.spl
@@ -421,10 +421,9 @@ $(obj)/$(SPL_BIN).sym: $(obj)/$(SPL_BIN) FORCE
 # May be overridden by arch/$(ARCH)/config.mk
 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 \
-		       $(patsubst $(obj)/%,%,$(u-boot-spl-main))  \
-		       $(patsubst $(obj)/%,%,$(u-boot-spl-platdata)) \
-		       --end-group \
+		       $(patsubst $(obj)/%,%,$(u-boot-spl-init)) \
+		       --whole-archive $(patsubst $(obj)/%,%,$(u-boot-spl-main)) --no-whole-archive \
+		       --start-group $(patsubst $(obj)/%,%,$(u-boot-spl-platdata)) --end-group \
 		       $(PLATFORM_LIBS) -Map $(SPL_BIN).map -o $(SPL_BIN))
 
 $(obj)/$(SPL_BIN): $(u-boot-spl-platdata) $(u-boot-spl-init) \
-- 
2.26.2