Avoid sort and recompose stages if all clusters simple

Even has measurable speedup...

src/hb-ot-shape-normalize.cc

@@ -319,6 +319,7 @@ _hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan,
 
   /* First round, decompose */
 
+  bool all_simple = true;
   buffer->clear_output ();
   count = buffer->len;
   buffer->idx = 0;
@@ -332,49 +333,53 @@ _hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan,
     if (end < count)
       end--; /* Leave one base for the marks to cluster with. */
 
-    /* From i to end are simple clusters. */
+    /* From idx to end are simple clusters. */
     while (buffer->idx < end && buffer->successful)
       decompose_current_character (&c, might_short_circuit);
 
     if (buffer->idx == count || !buffer->successful)
       break;
 
+    all_simple = false;
+
     /* Find all the marks now. */
     for (end = buffer->idx + 1; end < count; end++)
       if (!HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&buffer->info[end])))
         break;
 
+    /* idx to end is one non-simple cluster. */
     decompose_multi_char_cluster (&c, end, always_short_circuit);
   }
   while (buffer->idx < count && buffer->successful);
   buffer->swap_buffers ();
 
-
   /* Second round, reorder (inplace) */
-
-  count = buffer->len;
-  for (unsigned int i = 0; i < count; i++)
+  if (!all_simple)
   {
-    if (_hb_glyph_info_get_modified_combining_class (&buffer->info[i]) == 0)
-      continue;
+    count = buffer->len;
+    for (unsigned int i = 0; i < count; i++)
+    {
+      if (_hb_glyph_info_get_modified_combining_class (&buffer->info[i]) == 0)
+	continue;
+
+      unsigned int end;
+      for (end = i + 1; end < count; end++)
+	if (_hb_glyph_info_get_modified_combining_class (&buffer->info[end]) == 0)
+	  break;
+
+      /* We are going to do a O(n^2).  Only do this if the sequence is short. */
+      if (end - i > HB_OT_SHAPE_COMPLEX_MAX_COMBINING_MARKS) {
+	i = end;
+	continue;
+      }
 
-    unsigned int end;
-    for (end = i + 1; end < count; end++)
-      if (_hb_glyph_info_get_modified_combining_class (&buffer->info[end]) == 0)
-        break;
+      buffer->sort (i, end, compare_combining_class);
+
+      if (plan->shaper->reorder_marks)
+	plan->shaper->reorder_marks (plan, buffer, i, end);
 
-    /* We are going to do a O(n^2).  Only do this if the sequence is short. */
-    if (end - i > HB_OT_SHAPE_COMPLEX_MAX_COMBINING_MARKS) {
       i = end;
-      continue;
     }
-
-    buffer->sort (i, end, compare_combining_class);
-
-    if (plan->shaper->reorder_marks)
-      plan->shaper->reorder_marks (plan, buffer, i, end);
-
-    i = end;
   }
   if (buffer->scratch_flags & HB_BUFFER_SCRATCH_FLAG_HAS_CGJ)
   {
@@ -393,8 +398,9 @@ _hb_ot_shape_normalize (const hb_ot_shape_plan_t *plan,
 
   /* Third round, recompose */
 
-  if (mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS ||
-      mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT)
+  if (!all_simple &&
+      (mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS ||
+       mode == HB_OT_SHAPE_NORMALIZATION_MODE_COMPOSED_DIACRITICS_NO_SHORT_CIRCUIT))
   {
     /* As noted in the comment earlier, we don't try to combine
      * ccc=0 chars with their previous Starter. */