diff -r adcd9131b7c6 Objects/stringlib/fastsearch.h
--- a/Objects/stringlib/fastsearch.h	Fri Dec 09 00:41:46 2016 +0100
+++ b/Objects/stringlib/fastsearch.h	Fri Dec 09 18:03:35 2016 +0800
@@ -127,6 +127,65 @@
 }
 
 Py_LOCAL_INLINE(Py_ssize_t)
+STRINGLIB(count_char)(const STRINGLIB_CHAR* s, Py_ssize_t n,
+                      STRINGLIB_CHAR ch, Py_ssize_t maxcount)
+{
+    Py_ssize_t count = 0;
+#if STRINGLIB_SIZEOF_CHAR == 1
+# if SIZEOF_LONG == 4
+#  define FAST_COUNT_MASK 0x01010101ul
+# elif SIZEOF_LONG == 8
+#  define FAST_COUNT_MASK 0x0101010101010101ul
+# else
+#  error C 'long' size should be either 4 or 8!
+# endif
+    const STRINGLIB_CHAR *q = (const STRINGLIB_CHAR *)s;
+    const STRINGLIB_CHAR *e = (const STRINGLIB_CHAR *)s + n;
+    const STRINGLIB_CHAR *aligned_end =
+        (const STRINGLIB_CHAR *) _Py_ALIGN_DOWN(e, SIZEOF_LONG);
+    while (q < e) {
+        if (_Py_IS_ALIGNED(q, SIZEOF_LONG)) {
+            const STRINGLIB_CHAR *_q = q;
+            while (_q < aligned_end) {
+                unsigned long block = *(unsigned long *)_q;
+                /* If any byte equals to ch, then it's zero. */
+                unsigned long tmp = block ^ (FAST_COUNT_MASK * ch);
+                /* Count how many zero bytes in a long. */
+                count +=
+                    /* highest bits set only if byte is 0x0 or 0x80 */
+                    ((FAST_COUNT_MASK * 0x80 - ((tmp) & FAST_COUNT_MASK * 0x7f)) &
+                     /* highest bits set only if byte in [0x0, 0x80) */
+                     (~tmp & (FAST_COUNT_MASK * 0x80))) / 0x80 % 0xff;
+                /* assume not possible to overflow */
+                if (count >= maxcount)
+                    return maxcount;
+                _q += SIZEOF_LONG;
+            }
+            q = _q;
+            if (q >= e)
+                break;
+        }
+        if (*q++ == ch) {
+            count++;
+            if (count == maxcount)
+                return maxcount;
+        }
+    }
+# undef FAST_COUNT_MASK
+#else
+    int i;
+    for (i = 0; i < n; i++) {
+        if (s[i] == ch) {
+            count++;
+            if (count == maxcount)
+                return maxcount;
+        }
+    }
+#endif
+    return count;
+}
+
+Py_LOCAL_INLINE(Py_ssize_t)
 FASTSEARCH(const STRINGLIB_CHAR* s, Py_ssize_t n,
            const STRINGLIB_CHAR* p, Py_ssize_t m,
            Py_ssize_t maxcount, int mode)
@@ -150,15 +209,8 @@
         else if (mode == FAST_RSEARCH)
             return STRINGLIB(rfind_char)(s, n, p[0]);
         else {  /* FAST_COUNT */
-            for (i = 0; i < n; i++)
-                if (s[i] == p[0]) {
-                    count++;
-                    if (count == maxcount)
-                        return maxcount;
-                }
-            return count;
+            return STRINGLIB(count_char)(s, n, p[0], maxcount);
         }
-        return -1;
     }
 
     mlast = m - 1;