m32r: add __ucmpdi2 to fix build failure

We are having build failure with m32r and the error message being:

  ERROR: "__ucmpdi2" [lib/842/842_decompress.ko] undefined!
  ERROR: "__ucmpdi2" [fs/btrfs/btrfs.ko] undefined!
  ERROR: "__ucmpdi2" [drivers/scsi/sd_mod.ko] undefined!
  ERROR: "__ucmpdi2" [drivers/media/i2c/adv7842.ko] undefined!
  ERROR: "__ucmpdi2" [drivers/md/bcache/bcache.ko] undefined!
  ERROR: "__ucmpdi2" [drivers/iio/imu/inv_mpu6050/inv-mpu6050.ko] undefined!

__ucmpdi2 is introduced to m32r architecture taking example from other
architectures like h8300, microblaze, mips.

Link: http://lkml.kernel.org/r/1465509213-4280-1-git-send-email-sudipm.mukherjee@gmail.com
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/m32r/kernel/m32r_ksyms.c

@@ -41,6 +41,9 @@ EXPORT_SYMBOL(cpu_data);
 EXPORT_SYMBOL(smp_flush_tlb_page);
 #endif
 
+extern int __ucmpdi2(unsigned long long a, unsigned long long b);
+EXPORT_SYMBOL(__ucmpdi2);
+
 /* compiler generated symbol */
 extern void __ashldi3(void);
 extern void __ashrdi3(void);

arch/m32r/lib/Makefile

@@ -3,5 +3,5 @@
 #
 
 lib-y  := checksum.o ashxdi3.o memset.o memcpy.o \
-	  delay.o strlen.o usercopy.o csum_partial_copy.o
-
+	  delay.o strlen.o usercopy.o csum_partial_copy.o \
+	  ucmpdi2.o

arch/m32r/lib/libgcc.h

@@ -0,0 +1,23 @@
+#ifndef __ASM_LIBGCC_H
+#define __ASM_LIBGCC_H
+
+#include <asm/byteorder.h>
+
+#ifdef __BIG_ENDIAN
+struct DWstruct {
+	int high, low;
+};
+#elif defined(__LITTLE_ENDIAN)
+struct DWstruct {
+	int low, high;
+};
+#else
+#error I feel sick.
+#endif
+
+typedef union {
+	struct DWstruct s;
+	long long ll;
+} DWunion;
+
+#endif /* __ASM_LIBGCC_H */

arch/m32r/lib/ucmpdi2.c

@@ -0,0 +1,17 @@
+#include "libgcc.h"
+
+int __ucmpdi2(unsigned long long a, unsigned long long b)
+{
+	const DWunion au = {.ll = a};
+	const DWunion bu = {.ll = b};
+
+	if ((unsigned int)au.s.high < (unsigned int)bu.s.high)
+		return 0;
+	else if ((unsigned int)au.s.high > (unsigned int)bu.s.high)
+		return 2;
+	if ((unsigned int)au.s.low < (unsigned int)bu.s.low)
+		return 0;
+	else if ((unsigned int)au.s.low > (unsigned int)bu.s.low)
+		return 2;
+	return 1;
+}