diff --git a/src/hb-ot-shape-complex-arabic.cc b/src/hb-ot-shape-complex-arabic.cc
index 9720f7ab9..53e7a9b64 100644
--- a/src/hb-ot-shape-complex-arabic.cc
+++ b/src/hb-ot-shape-complex-arabic.cc
@@ -61,25 +61,25 @@ static unsigned int get_joining_type (hb_codepoint_t u, hb_unicode_general_categ
 {
   /* TODO Macroize the magic bit operations */
 
-  if (likely (JOINING_TABLE_FIRST <= u && u <= JOINING_TABLE_LAST)) {
+  if (likely (hb_codepoint_in_range (u, JOINING_TABLE_FIRST, JOINING_TABLE_LAST))) {
     unsigned int j_type = joining_table[u - JOINING_TABLE_FIRST];
     if (likely (j_type != JOINING_TYPE_X))
       return j_type;
   }
 
   /* Mongolian joining data is not in ArabicJoining.txt yet */
-  if (unlikely (0x1800 <= u && u <= 0x18AF))
+  if (unlikely (hb_codepoint_in_range (u, 0x1800, 0x18AF)))
   {
     /* All letters, SIBE SYLLABLE BOUNDARY MARKER, and NIRUGU are D */
     if (gen_cat == HB_UNICODE_GENERAL_CATEGORY_OTHER_LETTER || u == 0x1807 || u == 0x180A)
       return JOINING_TYPE_D;
   }
 
-  if (unlikely ((u & ~(0x200C^0x200D)) == 0x200C)) {
+  if (unlikely (hb_codepoint_in_range (u, 0x200C, 0x200D))) {
     return u == 0x200C ? JOINING_TYPE_U : JOINING_TYPE_C;
   }
 
-  return ((1<<gen_cat) & ((1<<HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)|(1<<HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK)|(1<<HB_UNICODE_GENERAL_CATEGORY_FORMAT))) ?
+  return (FLAG(gen_cat) & (FLAG(HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK) | FLAG(HB_UNICODE_GENERAL_CATEGORY_ENCLOSING_MARK) | FLAG(HB_UNICODE_GENERAL_CATEGORY_FORMAT))) ?
 	 JOINING_TYPE_T : JOINING_TYPE_U;
 }
 
diff --git a/src/hb-private.hh b/src/hb-private.hh
index 1cf11bcb7..b5745e74f 100644
--- a/src/hb-private.hh
+++ b/src/hb-private.hh
@@ -478,6 +478,25 @@ _hb_trace (const char *what,
 }
 
 
+/* Pre-mature optimization:
+ * Checks for lo <= u <= hi but with an optimization if lo and hi
+ * are only different in a contiguous set of lower-most bits.
+ */
+static inline bool
+hb_codepoint_in_range (hb_codepoint_t u, hb_codepoint_t lo, hb_codepoint_t hi)
+{
+  if ( ((lo^hi) & lo) == 0 &&
+       ((lo^hi) & hi) == (lo^hi) &&
+       ((lo^hi) & ((lo^hi) + 1)) == 0 )
+    return (u & ~(lo^hi)) == lo;
+  else
+    return lo <= u && u <= hi;
+}
+
+
+/* Useful for set-operations on small enums */
+#define FLAG(x) (1<<(x))
+
 HB_END_DECLS
 
 #endif /* HB_PRIVATE_HH */