xfs: remove custom do_div implementations

Long ago, all this gunk was added with a lament about problems
with gcc's do_div, and a fun recommendation in the changelog:

 egcs-2.91.66 is the recommended compiler version for building XFS.

All this special stuff was needed to work around an old gcc bug,
apparently, and it's been there ever since.

There should be no need for this anymore, so remove it.

Remove the special 32-bit xfs_do_mod as well; just let the
kernel's do_div() handle all this.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_linux.h

@@ -212,88 +212,6 @@ static inline kgid_t xfs_gid_to_kgid(__uint32_t gid)
 #define xfs_sort(a,n,s,fn)	sort(a,n,s,fn,NULL)
 #define xfs_stack_trace()	dump_stack()
 
-
-/* Move the kernel do_div definition off to one side */
-
-#if defined __i386__
-/* For ia32 we need to pull some tricks to get past various versions
- * of the compiler which do not like us using do_div in the middle
- * of large functions.
- */
-static inline __u32 xfs_do_div(void *a, __u32 b, int n)
-{
-	__u32	mod;
-
-	switch (n) {
-		case 4:
-			mod = *(__u32 *)a % b;
-			*(__u32 *)a = *(__u32 *)a / b;
-			return mod;
-		case 8:
-			{
-			unsigned long __upper, __low, __high, __mod;
-			__u64	c = *(__u64 *)a;
-			__upper = __high = c >> 32;
-			__low = c;
-			if (__high) {
-				__upper = __high % (b);
-				__high = __high / (b);
-			}
-			asm("divl %2":"=a" (__low), "=d" (__mod):"rm" (b), "0" (__low), "1" (__upper));
-			asm("":"=A" (c):"a" (__low),"d" (__high));
-			*(__u64 *)a = c;
-			return __mod;
-			}
-	}
-
-	/* NOTREACHED */
-	return 0;
-}
-
-/* Side effect free 64 bit mod operation */
-static inline __u32 xfs_do_mod(void *a, __u32 b, int n)
-{
-	switch (n) {
-		case 4:
-			return *(__u32 *)a % b;
-		case 8:
-			{
-			unsigned long __upper, __low, __high, __mod;
-			__u64	c = *(__u64 *)a;
-			__upper = __high = c >> 32;
-			__low = c;
-			if (__high) {
-				__upper = __high % (b);
-				__high = __high / (b);
-			}
-			asm("divl %2":"=a" (__low), "=d" (__mod):"rm" (b), "0" (__low), "1" (__upper));
-			asm("":"=A" (c):"a" (__low),"d" (__high));
-			return __mod;
-			}
-	}
-
-	/* NOTREACHED */
-	return 0;
-}
-#else
-static inline __u32 xfs_do_div(void *a, __u32 b, int n)
-{
-	__u32	mod;
-
-	switch (n) {
-		case 4:
-			mod = *(__u32 *)a % b;
-			*(__u32 *)a = *(__u32 *)a / b;
-			return mod;
-		case 8:
-			mod = do_div(*(__u64 *)a, b);
-			return mod;
-	}
-
-	/* NOTREACHED */
-	return 0;
-}
-
 /* Side effect free 64 bit mod operation */
 static inline __u32 xfs_do_mod(void *a, __u32 b, int n)
 {
@@ -310,10 +228,7 @@ static inline __u32 xfs_do_mod(void *a, __u32 b, int n)
 	/* NOTREACHED */
 	return 0;
 }
-#endif
 
-#undef do_div
-#define do_div(a, b)	xfs_do_div(&(a), (b), sizeof(a))
 #define do_mod(a, b)	xfs_do_mod(&(a), (b), sizeof(a))
 
 static inline __uint64_t roundup_64(__uint64_t x, __uint32_t y)