[U-Boot] [U-Boot, 1/2] common: Add CCACHE variable to allow use of ccache

[Marek Vasut <marex@denx.de>]

Dear sun york-R58495,

> On Aug 21, 2013, at 7:51 PM, Marek Vasut wrote:
> > Dear York Sun,
> > 
> >> On 05/20/2013 10:25 AM, Marek Vasut wrote:
> >>> Prefix HOSTCC and CC with CCACHE variable to allow easy use of ccache.
> >>> In case the user wants to use ccache, exporting CCACHE=ccache will do
> >>> the trick. It is of course possible to either make the cross-compiler
> >>> name into a shellscript which invokes the ccache and the compiler, but
> >>> setting this variable makes use of ccache easier and more convenient.
> >>> 
> >>> Using ccache becomes convenient when using MAKEALL for large build
> >>> tests, where the speedup after building the cache for the first time
> >>> is about 4-6 times.
> >>> 
> >>> Signed-off-by: Marek Vasut <marex@denx.de>
> >>> Cc: Tom Rini <trini@ti.com>
> >>> 
> >>> ---
> >>> config.mk |    8 +++++---
> >>> 
> >>> 1 file changed, 5 insertions(+), 3 deletions(-)
> >>> 
> >>> diff --git a/config.mk b/config.mk
> >>> index 1fd109f..d59ded2 100644
> >>> --- a/config.mk
> >>> +++ b/config.mk
> >>> @@ -98,6 +98,8 @@ else
> >>> 
> >>> HOSTCC		= gcc
> >>> endif
> >>> 
> >>> +HOSTCC		:= $(CCACHE) $(HOSTCC)
> >>> +
> >>> 
> >>> ifeq ($(HOSTOS),cygwin)
> >>> HOSTCFLAGS	+= -ansi
> >>> endif
> >>> 
> >>> @@ -140,13 +142,13 @@ binutils-version = $(shell $(SHELL)
> >>> $(SRCTREE)/tools/binutils-version.sh $(AS))
> >>> 
> >>> #
> >>> # Include the make variables (CC, etc...)
> >>> #
> >>> 
> >>> -AS	= $(CROSS_COMPILE)as
> >>> +AS	= $(CCACHE) $(CROSS_COMPILE)as
> >>> 
> >>> # Always use GNU ld
> >>> LD	= $(shell if $(CROSS_COMPILE)ld.bfd -v > /dev/null 2>&1; \
> >>> 
> >>> 		then echo "$(CROSS_COMPILE)ld.bfd"; else echo
> > 
> > "$(CROSS_COMPILE)ld";
> > 
> >>> 		fi;)
> >>> 
> >>> -CC	= $(CROSS_COMPILE)gcc
> >>> +CC	= $(CCACHE) $(CROSS_COMPILE)gcc
> >>> 
> >>> CPP	= $(CC) -E
> >>> AR	= $(CROSS_COMPILE)ar
> >>> NM	= $(CROSS_COMPILE)nm
> >>> 
> >>> @@ -320,7 +322,7 @@ endif
> >>> 
> >>> #######################################################################
> >>> # #
> >>> 
> >>> -export	HOSTCC HOSTCFLAGS HOSTLDFLAGS PEDCFLAGS HOSTSTRIP CROSS_COMPILE
> > 
> > \
> > 
> >>> +export	HOSTCC HOSTCFLAGS HOSTLDFLAGS PEDCFLAGS HOSTSTRIP CROSS_COMPILE
> >>> CCACHE \
> >>> 
> >>> 	AS LD CC CPP AR NM STRIP OBJCOPY OBJDUMP MAKE
> >>> 
> >>> export	CONFIG_SYS_TEXT_BASE PLATFORM_CPPFLAGS PLATFORM_RELFLAGS
> > 
> > CPPFLAGS
> > 
> >>> CFLAGS AFLAGS
> >> 
> >> Where did this patch go? I found it useful.
> > 
> > It needs additional fixes, try running with MAKEALL and you will see the
> > problem -- the problem is you would need separate ccache for each
> > MAKEALL thread.
> 
> I didn't use this patch but I modified config.mk as this patch did. MAKEALL
> works fine for "-a powerpc". It cuts my compiling time more than half for
> 660+ boards.

That is still poor, it should be much faster. If you use separate ccache for 
each board, then it will be _much_ more performant.

The problem is that when rebuilding all of those 680 configurations, the cached 
files get replaced by ones based on different board config all the time => you 
need to rebuild them => you loose performance.

Best regards,
Marek Vasut