kbuild: improve Kbuild speed

Kbuild brought about many advantages for us but a significant
performance regression was reported by Simon Glass.

After some discussions and analysis, it turned out
its main cause is in $(call cc-option,...).

Historically, U-Boot parses all config.mk
(arch/*/config.mk and board/*/config.mk)
every time descending into subdirectories.
That means cc-options are evaluated over and over again.

$(call cc-option,...) is useful but costly.
So we want to evaluate them only in ./Makefile
and spl/Makefile and export compiler flags.

This commit changes the build system as follows:

  - Modify scripts/Makefile.build to not include config.mk
    Instead, add $(PLATFORM_CPPFLAGS) to asflags-y, ccflags-y,
    cppflags-y.

  - Export many variables
    Going forward, Kbuild will not parse config.mk files
    when it descends into subdirectories.
    If we want to set variables in config.mk and use them
    in subdirectories, they must be exported.

    This is the list of variables to get exported:
      PLATFORM_CPPFLAGS
      CPUDIR
      BOARDDIR
      OBJCOPYFLAGS
      LDFLAGS
      LDFLAGS_FINAL
        (used in nand_spl/board/*/*/Makefile)
      CONFIG_STANDALONE_LOAD_ADDR
        (used in examples/standalone/Makefile)
      SYM_PREFIX
        (used in examples/standalone/Makefile)
      RELFLAGS
        (used in examples/standalone/Makefile)

  - Delete CPPFLAGS
    This variable has been replaced with PLATFORM_CPPFLAGS

  - Copy gcclibdir from example/standalone/Makefile
    to arch/sparc/config.mk
    The reference in CONFIG_STANDALONE_LOAD_ADDR must be
    resolved before it is exported.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Reported-by: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org> [on Sandbox]
Tested-by: Stephen Warren <swarren@nvidia.com> [on Tegra]

8 files changed, 44 insertions, 31 deletions

diff --git a/Makefile b/Makefile
index 4e61ae914c..c03a1b4ac7 100644
--- a/Makefile
+++ b/Makefile
@@ -358,13 +358,13 @@ UBOOTRELEASE = $(shell cat include/config/uboot.release 2> /dev/null)
 UBOOTVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
 
 export VERSION PATCHLEVEL SUBLEVEL UBOOTRELEASE UBOOTVERSION
-export ARCH CPU BOARD VENDOR SOC
+export ARCH CPU BOARD VENDOR SOC CPUDIR BOARDDIR
 export CONFIG_SHELL HOSTCC HOSTCFLAGS HOSTLDFLAGS CROSS_COMPILE AS LD CC
 export CPP AR NM LDR STRIP OBJCOPY OBJDUMP
 export MAKE AWK
 export DTC CHECK CHECKFLAGS
 
-export KBUILD_CPPFLAGS NOSTDINC_FLAGS UBOOTINCLUDE
+export KBUILD_CPPFLAGS NOSTDINC_FLAGS UBOOTINCLUDE OBJCOPYFLAGS LDFLAGS
 export KBUILD_CFLAGS KBUILD_AFLAGS
 
 # When compiling out-of-tree modules, put MODVERDIR in the module
@@ -567,7 +567,8 @@ NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
 CHECKFLAGS     += $(NOSTDINC_FLAGS)
 
 # FIX ME
-cpp_flags := $(KBUILD_CPPFLAGS) $(CPPFLAGS) $(UBOOTINCLUDE) $(NOSTDINC_FLAGS)
+cpp_flags := $(KBUILD_CPPFLAGS) $(PLATFORM_CPPFLAGS) $(UBOOTINCLUDE) \
+							$(NOSTDINC_FLAGS)
 c_flags := $(KBUILD_CFLAGS) $(cpp_flags)
 
 #########################################################################
diff --git a/arch/blackfin/config.mk b/arch/blackfin/config.mk
index adc97125b5..fcaa44f1d6 100644
--- a/arch/blackfin/config.mk
+++ b/arch/blackfin/config.mk
@@ -43,6 +43,7 @@ CREATE_LDR_ENV =
 endif
 
 SYM_PREFIX = _
+export SYM_PREFIX
 
 LDR_FLAGS-y :=
 LDR_FLAGS-$(CONFIG_BFIN_BOOTROM_USES_EVT1) += -J
diff --git a/arch/sparc/config.mk b/arch/sparc/config.mk
index 6dbf20f537..be59f58190 100644
--- a/arch/sparc/config.mk
+++ b/arch/sparc/config.mk
@@ -9,6 +9,8 @@ ifeq ($(CROSS_COMPILE),)
 CROSS_COMPILE := sparc-elf-
 endif
 
+gcclibdir := $(shell dirname `$(CC) -print-libgcc-file-name`)
+
 CONFIG_STANDALONE_LOAD_ADDR ?= 0x00000000 -L $(gcclibdir) \
 			       -T $(srctree)/examples/standalone/sparc.lds
 
diff --git a/config.mk b/config.mk
index af25c115cc..4657577f9d 100644
--- a/config.mk
+++ b/config.mk
@@ -6,11 +6,18 @@
 #
 #########################################################################
 
-# clean the slate ...
-PLATFORM_RELFLAGS =
-PLATFORM_CPPFLAGS =
-PLATFORM_LDFLAGS =
-
+# This file is included from ./Makefile and spl/Makefile.
+# Clean the state to avoid the same flags added twice.
+#
+# (Tegra needs different flags for SPL.
+#  That's the reason why this file must be included from spl/Makefile too.
+#  If we did not have Tegra SoCs, build system would be much simpler...)
+PLATFORM_RELFLAGS :=
+PLATFORM_CPPFLAGS :=
+PLATFORM_LDFLAGS :=
+LDFLAGS :=
+LDFLAGS_FINAL :=
+OBJCOPYFLAGS :=
 #########################################################################
 
 # Some architecture config.mk files need to know what CPUDIR is set to,
@@ -41,12 +48,17 @@ endif
 
 #########################################################################
 
-RELFLAGS= $(PLATFORM_RELFLAGS)
+RELFLAGS := $(PLATFORM_RELFLAGS)
 
 OBJCOPYFLAGS += --gap-fill=0xff
 
-CPPFLAGS = $(RELFLAGS)
-CPPFLAGS += -pipe $(PLATFORM_CPPFLAGS)
+PLATFORM_CPPFLAGS += $(RELFLAGS)
+PLATFORM_CPPFLAGS += -pipe
 
 LDFLAGS += $(PLATFORM_LDFLAGS)
 LDFLAGS_FINAL += -Bstatic
+
+export PLATFORM_CPPFLAGS
+export RELFLAGS
+export LDFLAGS_FINAL
+export CONFIG_STANDALONE_LOAD_ADDR
diff --git a/examples/standalone/Makefile b/examples/standalone/Makefile
index 5b227cd898..7e0e5b71b6 100644
--- a/examples/standalone/Makefile
+++ b/examples/standalone/Makefile
@@ -44,9 +44,8 @@ gcclibdir := $(shell dirname `$(CC) -print-libgcc-file-name`)
 # relocatable executable.  The relocation data is not needed, and
 # also causes the entry point of the standalone application to be
 # inconsistent.
-ifeq ($(ARCH),powerpc)
-# FIX ME
-CPPFLAGS := $(filter-out $(RELFLAGS), $(CPPFLAGS))
+ifeq ($(CONFIG_PPC),y)
+PLATFORM_CPPFLAGS := $(filter-out $(RELFLAGS),$(PLATFORM_CPPFLAGS))
 endif
 
 # We don't want gcc reordering functions if possible.  This ensures that an
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 59361f4d7a..36346fd161 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -55,11 +55,6 @@ endif
 
 include scripts/Kbuild.include
 
-# Added for U-Boot
-# We must include config.mk after Kbuild.include
-# so that some config.mk can use cc-option.
-include config.mk
-
 # For backward compatibility check that these variables do not change
 save-cflags := $(CFLAGS)
 
@@ -68,6 +63,11 @@ kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
 kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
 include $(kbuild-file)
 
+# Added for U-Boot
+asflags-y  += $(PLATFORM_CPPFLAGS)
+ccflags-y  += $(PLATFORM_CPPFLAGS)
+cppflags-y += $(PLATFORM_CPPFLAGS)
+
 # If the save-* variables changed error out
 ifeq ($(KBUILD_NOPEDANTIC),)
         ifneq ("$(save-cflags)","$(CFLAGS)")
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 02b17b1057..d568fde2cc 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -101,13 +101,12 @@ basename_flags = -D"KBUILD_BASENAME=KBUILD_STR($(call name-fix,$(basetarget)))"
 modname_flags  = $(if $(filter 1,$(words $(modname))),\
                  -D"KBUILD_MODNAME=KBUILD_STR($(call name-fix,$(modname)))")
 
-# U-Boot also uses $(CPPFLAGS)
-orig_c_flags   = $(KBUILD_CPPFLAGS) $(CPPFLAGS) $(KBUILD_CFLAGS) $(KBUILD_SUBDIR_CCFLAGS) \
+orig_c_flags   = $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(KBUILD_SUBDIR_CCFLAGS) \
                  $(ccflags-y) $(CFLAGS_$(basetarget).o)
 _c_flags       = $(filter-out $(CFLAGS_REMOVE_$(basetarget).o), $(orig_c_flags))
-_a_flags       = $(KBUILD_CPPFLAGS) $(CPPFLAGS) $(KBUILD_AFLAGS) $(KBUILD_SUBDIR_ASFLAGS) \
+_a_flags       = $(KBUILD_CPPFLAGS) $(KBUILD_AFLAGS) $(KBUILD_SUBDIR_ASFLAGS) \
                  $(asflags-y) $(AFLAGS_$(basetarget).o)
-_cpp_flags     = $(KBUILD_CPPFLAGS) $(CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(@F))
+_cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(@F))
 
 #
 # Enable gcov profiling flags for a file, directory or for all files depending
diff --git a/spl/Makefile b/spl/Makefile
index e1a0601a02..bb3d3495e4 100644
--- a/spl/Makefile
+++ b/spl/Makefile
@@ -29,10 +29,6 @@ ifeq ($(CONFIG_TPL_BUILD),y)
 KBUILD_CPPFLAGS += -DCONFIG_TPL_BUILD
 endif
 
-# Enable garbage collection of un-used sections for SPL
-KBUILD_CFLAGS += -ffunction-sections -fdata-sections
-LDFLAGS_FINAL += --gc-sections
-
 ifeq ($(CONFIG_TPL_BUILD),y)
 export CONFIG_TPL_BUILD
 SPL_BIN := u-boot-tpl
@@ -50,8 +46,14 @@ endif
 
 include $(TOPDIR)/config.mk
 
+# Enable garbage collection of un-used sections for SPL
+KBUILD_CFLAGS += -ffunction-sections -fdata-sections
+LDFLAGS_FINAL += --gc-sections
+
 # FIX ME
-c_flags := $(KBUILD_CFLAGS) $(KBUILD_CPPFLAGS) $(CPPFLAGS) $(UBOOTINCLUDE) $(NOSTDINC_FLAGS)
+cpp_flags := $(KBUILD_CPPFLAGS) $(PLATFORM_CPPFLAGS) $(UBOOTINCLUDE) \
+							$(NOSTDINC_FLAGS)
+c_flags := $(KBUILD_CFLAGS) $(cpp_flags)
 
 # Auto-generate the spl-autoconf.mk file (which is included by all makefiles for SPL)
 quiet_cmd_autoconf = GEN     $@
@@ -228,9 +230,6 @@ PHONY += $(u-boot-spl-dirs)
 $(u-boot-spl-dirs):
 	$(Q)$(MAKE) $(build)=$@
 
-# FIX ME
-cpp_flags := $(KBUILD_CPPFLAGS) $(CPPFLAGS) $(UBOOTINCLUDE) $(NOSTDINC_FLAGS)
-
 quiet_cmd_cpp_lds = LDS     $@
 cmd_cpp_lds = $(CPP) $(cpp_flags) $(LDPPFLAGS) -ansi -D__ASSEMBLY__ \
 		-x assembler-with-cpp -P -o $@ $<