[SPARC32]: Add __cmpdi2() libcall implementation ala. MIPS.

Device mapper generates calls to this with recent versions
of gcc.

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/lib/Makefile

@@ -8,6 +8,7 @@ lib-y := mul.o rem.o sdiv.o udiv.o umul.o urem.o ashrdi3.o memcpy.o memset.o \
          strlen.o checksum.o blockops.o memscan.o memcmp.o strncmp.o \
 	 strncpy_from_user.o divdi3.o udivdi3.o strlen_user.o \
 	 copy_user.o locks.o atomic.o \
-	 lshrdi3.o ashldi3.o rwsem.o muldi3.o bitext.o
+	 lshrdi3.o ashldi3.o rwsem.o muldi3.o bitext.o \
+	 cmpdi2.o
 
 obj-y += iomap.o atomic32.o

arch/sparc/lib/cmpdi2.c

@@ -0,0 +1,27 @@
+#include <linux/module.h>
+
+#include "libgcc.h"
+
+word_type __cmpdi2(long long a, long long b)
+{
+	const DWunion au = {
+		.ll = a
+	};
+	const DWunion bu = {
+		.ll = b
+	};
+
+	if (au.s.high < bu.s.high)
+		return 0;
+	else if (au.s.high > 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;
+}
+
+EXPORT_SYMBOL(__cmpdi2);

arch/sparc/lib/libgcc.h

@@ -0,0 +1,18 @@
+#ifndef __ASM_LIBGCC_H
+#define __ASM_LIBGCC_H
+
+#include <asm/byteorder.h>
+
+typedef int word_type __attribute__ ((mode (__word__)));
+
+struct DWstruct {
+	int high, low;
+};
+
+typedef union
+{
+	struct DWstruct s;
+	long long ll;
+} DWunion;
+
+#endif /* __ASM_LIBGCC_H */