chao.an b88561299b make/expression: improving up asm/C/C++ compile times ... In the current compilation environment, the recursive assignment(=) for compile flags will be delayed until every file is actually need to be compile. For example: -------------------------------------------------------------------------------- arch/arm/src/Makefile: INCLUDES += ${shell $(INCDIR) "$(CC)" $(ARCH_SRCDIR)$(DELIM)chip} INCLUDES += ${shell $(INCDIR) "$(CC)" $(ARCH_SRCDIR)$(DELIM)common} INCLUDES += ${shell $(INCDIR) "$(CC)" $(ARCH_SRCDIR)$(DELIM)$(ARCH_SUBDIR)} INCLUDES += ${shell $(INCDIR) "$(CC)" $(TOPDIR)$(DELIM)sched} CPPFLAGS += $(INCLUDES) $(EXTRAFLAGS) CFLAGS += $(INCLUDES) $(EXTRAFLAGS) CXXFLAGS += $(INCLUDES) $(EXTRAFLAGS) AFLAGS += $(INCLUDES) $(EXTRAFLAGS) -------------------------------------------------------------------------------- All compilation options will be included recursively, which will be delayed until the compilation options are actually used: tools/Config.mk: -------------------------------------------------------------------------------- define COMPILE @echo "CC: $1" $(Q) $(CC) -c $(CFLAGS) $($(strip $1)_CFLAGS) $1 -o $2 endef -------------------------------------------------------------------------------- All compile flags to be reexecuted $(INCDIR) as long as one file needs to be compiled, but in fact, the compilation options have not changed in the current directory. So the we recommand to change the syntax of assignment From Recursive (=) To Simple (:=) In this way, we can ensure that all compilation options are expanded only once and reducing repeated works. Signed-off-by: chao.an <anchao@xiaomi.com>		2020-11-02 07:53:53 -08:00
..
ea3152.ld	Linker scripts: Fix some alignment problems.	2019-09-15 18:06:36 -06:00
Make.defs	make/expression: improving up asm/C/C++ compile times	2020-11-02 07:53:53 -08:00