[U-Boot] [PATCH v2 4/4] kbuild: improve Kbuild speed

Masahiro Yamada yamada.m at jp.panasonic.com
Fri Feb 28 05:23:41 CET 2014 

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 at jp.panasonic.com>
Reported-by: Simon Glass <sjg at chromium.org>
Tested-by: Stephen Warren <swarren at nvidia.com>
---

Changes in v2: None

 Makefile                     |  7 ++++---
 arch/blackfin/config.mk      |  1 +
 arch/sparc/config.mk         |  2 ++
 config.mk                    | 28 ++++++++++++++++++++--------
 examples/standalone/Makefile |  5 ++---
 scripts/Makefile.build       | 10 +++++-----
 scripts/Makefile.lib         |  7 +++----
 spl/Makefile                 |  7 +++----
 8 files changed, 40 insertions(+), 27 deletions(-)

diff --git a/Makefile b/Makefile
index 56ba1ef..e49a240 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 c752025..8510e1c 100644
--- a/arch/blackfin/config.mk
+++ b/arch/blackfin/config.mk
@@ -41,6 +41,7 @@ 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 154d00e..7daf4ef 100644
--- a/arch/sparc/config.mk
+++ b/arch/sparc/config.mk
@@ -7,6 +7,8 @@
 
 CROSS_COMPILE ?= sparc-elf-
 
+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 e59697f..bb3da0d 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,
@@ -39,12 +46,17 @@ 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 5b227cd..7e0e5b7 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 59361f4..36346fd 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 02b17b1..d568fde 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 e1a0601..781abf6 100644
--- a/spl/Makefile
+++ b/spl/Makefile
@@ -51,7 +51,9 @@ endif
 include $(TOPDIR)/config.mk
 
 # 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 $@ $<
-- 
1.8.3.2

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