diff --git a/mercurial/thirdparty/xdiff/xprepare.c b/mercurial/thirdparty/xdiff/xprepare.c
--- a/mercurial/thirdparty/xdiff/xprepare.c
+++ b/mercurial/thirdparty/xdiff/xprepare.c
@@ -70,7 +70,7 @@
 static int xdl_init_classifier(xdlclassifier_t *cf, int64_t size, int64_t flags) {
 	cf->flags = flags;
 
-	cf->hbits = xdl_hashbits((unsigned int) size);
+	cf->hbits = xdl_hashbits(size);
 	cf->hsize = 1 << cf->hbits;
 
 	if (xdl_cha_init(&cf->ncha, sizeof(xdlclass_t), size / 4 + 1) < 0) {
@@ -262,7 +262,7 @@
 		goto abort;
 
 	{
-		hbits = xdl_hashbits((unsigned int) narec);
+		hbits = xdl_hashbits(narec);
 		hsize = 1 << hbits;
 		if (!(rhash = (xrecord_t **) xdl_malloc(hsize * sizeof(xrecord_t *))))
 			goto abort;
diff --git a/mercurial/thirdparty/xdiff/xutils.h b/mercurial/thirdparty/xdiff/xutils.h
--- a/mercurial/thirdparty/xdiff/xutils.h
+++ b/mercurial/thirdparty/xdiff/xutils.h
@@ -32,7 +32,7 @@
 int64_t xdl_guess_lines(mmfile_t *mf, int64_t sample);
 int xdl_recmatch(const char *l1, int64_t s1, const char *l2, int64_t s2);
 uint64_t xdl_hash_record(char const **data, char const *top);
-unsigned int xdl_hashbits(unsigned int size);
+unsigned int xdl_hashbits(int64_t size);
 
 
 
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
@@ -141,9 +141,10 @@
 	return ha;
 }
 
-unsigned int xdl_hashbits(unsigned int size) {
-	unsigned int val = 1, bits = 0;
+unsigned int xdl_hashbits(int64_t size) {
+	int64_t val = 1;
+	unsigned int bits = 0;
 
-	for (; val < size && bits < CHAR_BIT * sizeof(unsigned int); val <<= 1, bits++);
+	for (; val < size && bits < (int64_t) CHAR_BIT * sizeof(unsigned int); val <<= 1, bits++);
 	return bits ? bits: 1;
 }