[ot-tag] Cache last bsearch result

Part of #3591 Humm. Looks like not all of the fat is bsearch overhead now. I cached the last bsearch result, but most of the time is still there. I'm baffled. Before: ------------------------------------------------------------------------------------------------ Benchmark Time CPU Iterations ------------------------------------------------------------------------------------------------ BM_hb_ot_tags_from_script_and_language/COMMON abcd_XY 8.08 ns 8.05 ns 84500482 BM_hb_ot_tags_from_script_and_language/COMMON zh_CN 42.2 ns 42.1 ns 16722006 BM_hb_ot_tags_from_script_and_language/COMMON en_US 16.1 ns 16.0 ns 43461527 BM_hb_ot_tags_from_script_and_language/LATIN en_US 16.5 ns 16.5 ns 42448505 BM_hb_ot_tags_from_script_and_language/COMMON none 4.34 ns 4.33 ns 161290530 BM_hb_ot_tags_from_script_and_language/LATIN none 4.34 ns 4.33 ns 162339799 After: ------------------------------------------------------------------------------------------------ Benchmark Time CPU Iterations ------------------------------------------------------------------------------------------------ BM_hb_ot_tags_from_script_and_language/COMMON abcd_XY 8.13 ns 8.11 ns 80438134 BM_hb_ot_tags_from_script_and_language/COMMON zh_CN 40.0 ns 39.9 ns 17487939 BM_hb_ot_tags_from_script_and_language/COMMON en_US 12.7 ns 12.7 ns 55124394 BM_hb_ot_tags_from_script_and_language/LATIN en_US 13.1 ns 13.0 ns 53660125 BM_hb_ot_tags_from_script_and_language/COMMON none 4.61 ns 4.60 ns 151394104 BM_hb_ot_tags_from_script_and_language/LATIN none 4.70 ns 4.68 ns 150402847
harfbuzz · May 17, 2022 · dfca47f · dfca47f
1 parent 909f00a
commit dfca47f
Showing 1 changed file with 9 additions and 2 deletions.
diff --git a/src/hb-ot-tag.cc b/src/hb-ot-tag.cc
@@ -257,7 +257,6 @@ hb_ot_tags_from_language (const char   *lang_str,
 			  hb_tag_t     *tags)
 {
   const char *s;
-  unsigned int tag_idx;
 
   /* Check for matches of multiple subtags. */
   if (hb_ot_tags_from_complex_language (lang_str, limit, count, tags))
@@ -288,8 +287,16 @@ hb_ot_tags_from_language (const char   *lang_str,
       ot_languages = ot_languages3;
       ot_languages_len = ARRAY_LENGTH (ot_languages3);
     }
-    if (hb_sorted_array (ot_languages, ot_languages_len).bfind (hb_tag_from_string (lang_str, first_len), &tag_idx))
+
+    hb_tag_t lang_tag = hb_tag_from_string (lang_str, first_len);
+
+    static unsigned last_tag_idx; /* Poor man's cache. */
+    unsigned tag_idx = last_tag_idx;
+
+    if ((tag_idx < ot_languages_len && ot_languages[tag_idx].language == lang_tag) ||
+	hb_sorted_array (ot_languages, ot_languages_len).bfind (lang_tag, &tag_idx))
     {
+      last_tag_idx = tag_idx;
       unsigned int i;
       while (tag_idx != 0 &&
 	     ot_languages[tag_idx].language == ot_languages[tag_idx - 1].language)