求助：编译U－boot

有没有人编译u-boot的时候遇到这种问题？
make[1]: Leaving directory `/download/u-boot/post'
make[1]: Entering directory `/download/u-boot/post/cpu'
make[1]: *** No rule to make target `asm.S', needed by `.depend'.  Stop.
make[1]: Leaving directory `/download/u-boot/post/cpu'
make: *** [depend] Error 2　　　　　　

找不到asm.S文件吧　　　　　　

不应该啊！下面是Makefile里面的：
SUBDIRS =

LIB        = libcpu.a

AOBJS        = asm.o
COBJS        = cmp.o cmpi.o two.o twox.o three.o threex.o
COBJS   += threei.o andi.o srawi.o rlwnm.o rlwinm.o rlwimi.o
COBJS        += store.o load.o cr.o b.o multi.o string.o complex.o

include $(TOPDIR)/post/rules.mk
上层文件夹里的rule.mk如下：
include $(TOPDIR)/config.mk

OBJS        = $(AOBJS) $(COBJS)

CPPFLAGS += -I$(TOPDIR)

all:        $(LIB)

$(LIB):        .depend $(OBJS)
        $(AR) crv $@ $(OBJS)

#########################################################################

.depend: Makefile $(AOBJS:.o=.S) $(COBJS:.o=.c)
        $(CC) -M $(CFLAGS) $(AOBJS:.o=.S) $(COBJS:.o=.c) > .depend

sinclude .depend

#########################################################################