On 27 February 2014 21:23, Masahiro Yamada yamada.m@jp.panasonic.comwrote:
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 Tested-by: Stephen Warren swarren@nvidia.com
Acked-by: Simon Glass sjg@chromium.org
Tested only on sandbox:
Tested-by: Simon Glass sjg@chromium.org