arc: build libgcc in U-Boot

This way we may have very limited set of functions implemented so we
save some space.

Also it allows us to build U-Boot for any ARC core with the same one
toolchain because we don't rely on pre-built libgcc.

For example:
 * we may use little-endian toolchain but build U-Boot for ether
endianess
 * we may use non-multilibbed uClibc toolchain but build U-Boot for
whatever ARC CPU flavour that current GCC supports

Private libgcc built from generic C implementation contributes only 144
bytes to .text section so we don't see significant degradation of size:
--->8---
$ arc-linux-size u-boot.libgcc-prebuilt
   text	   data	    bss	    dec	    hex	filename
 222217	  24912	 214820	 461949	  70c7d	u-boot.libgcc-prebuilt

$ arc-linux-size u-boot.libgcc-private
   text	   data	    bss	    dec	    hex	filename
 222361	  24912	 214820	 462093	  70d0d	u-boot.libgcc-private
--->8---

Also I don't notice visible performance degradation compared to
pre-built libgcc (where at least "*div*" functions are had-written in
assembly) on typical operations of downloading 10Mb uImage over TFTP and
bootm.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/arc/lib/Makefile b/arch/arc/lib/Makefile
index bae4419..b8028c9 100644
--- a/arch/arc/lib/Makefile
+++ b/arch/arc/lib/Makefile
@@ -20,3 +20,5 @@ obj-y += reset.o
 obj-y += timer.o
 
 obj-$(CONFIG_CMD_BOOTM) += bootm.o
+
+lib-$(CONFIG_USE_PRIVATE_LIBGCC) += _millicodethunk.o libgcc2.o