diff --git a/mercurial/thirdparty/xdiff/xutils.c b/mercurial/thirdparty/xdiff/xutils.c
--- a/mercurial/thirdparty/xdiff/xutils.c
+++ b/mercurial/thirdparty/xdiff/xutils.c
@@ -22,10 +22,13 @@
 
 #include <limits.h>
 #include <assert.h>
-#include "xinclude.h"
 
+/* Define XXHASH functions in a custom namespace */
+#define XXH_NAMESPACE XDIFF_
+#define XXH_PRIVATE_API
+#include "thirdparty/xxhash/xxhash.h"
 
-
+#include "xinclude.h"
 
 long xdl_bogosqrt(long n) {
 	long i;
@@ -299,19 +302,16 @@
 }
 
 unsigned long xdl_hash_record(char const **data, char const *top, long flags) {
-	unsigned long ha = 5381;
+	XXH32_hash_t h;
 	char const *ptr = *data;
 
 	if (flags & XDF_WHITESPACE_FLAGS)
 		return xdl_hash_record_with_whitespace(data, top, flags);
 
-	for (; ptr < top && *ptr != '\n'; ptr++) {
-		ha += (ha << 5);
-		ha ^= (unsigned long) *ptr;
-	}
+	for (; ptr < top && *ptr != '\n'; ptr++) { }
+	h = XDIFF_XXH32(*data, ptr - *data + 1, 0);
 	*data = ptr < top ? ptr + 1: ptr;
-
-	return ha;
+	return h;
 }
 
 unsigned int xdl_hashbits(unsigned int size) {
diff --git a/setup.py b/setup.py
--- a/setup.py
+++ b/setup.py
@@ -871,9 +871,13 @@
               include_dirs=common_include_dirs,
               depends=common_depends),
     Extension('mercurial.cext.bdiff', ['mercurial/bdiff.c',
-                                       'mercurial/cext/bdiff.c'] + xdiff_srcs,
+                                       'mercurial/cext/bdiff.c',
+                                       'mercurial/thirdparty/xxhash/xxhash.c',
+                                       ] + xdiff_srcs,
               include_dirs=common_include_dirs,
-              depends=common_depends + ['mercurial/bdiff.h'] + xdiff_headers),
+              depends=common_depends + ['mercurial/bdiff.h',
+                                        'mercurial/thirdparty/xxhash/xxhash.h',
+                                        ] + xdiff_headers),
     Extension('mercurial.cext.diffhelpers', ['mercurial/cext/diffhelpers.c'],
               include_dirs=common_include_dirs,
               depends=common_depends),