From 6463ee02d6127fa2bfc4ada5e65468a4f8815531 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 21 Jan 2021 12:01:13 -0700
Subject: [PATCH] Speed up ClassDef/Coverage intersect methods

Just avoiding overhead as measured by Garret.
Should rewrite as dagger in the future and confirm that it has the
same benefits. Later on, rewrite as lfind() maybe.

Fixes https://github.com/harfbuzz/harfbuzz/issues/2826
---
 src/hb-ot-layout-common.hh | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/hb-ot-layout-common.hh b/src/hb-ot-layout-common.hh
index 6ab950a32..3a169163a 100644
--- a/src/hb-ot-layout-common.hh
+++ b/src/hb-ot-layout-common.hh
@@ -1251,8 +1251,9 @@ struct CoverageFormat1
   {
     /* TODO Speed up, using hb_set_next() and bsearch()? */
     unsigned int count = glyphArray.len;
+    const HBGlyphID *arr = glyphArray.arrayZ;
     for (unsigned int i = 0; i < count; i++)
-      if (glyphs->has (glyphArray[i]))
+      if (glyphs->has (arr[i]))
 	return true;
     return false;
   }
@@ -1356,18 +1357,21 @@ struct CoverageFormat2
   bool intersects (const hb_set_t *glyphs) const
   {
     /* TODO Speed up, using hb_set_next() and bsearch()? */
-    unsigned int count = rangeRecord.len;
-    for (unsigned int i = 0; i < count; i++)
-      if (rangeRecord[i].intersects (glyphs))
+    /* TODO Rewrite as dagger. */
+    unsigned count = rangeRecord.len;
+    const RangeRecord *arr = rangeRecord.arrayZ;
+    for (unsigned i = 0; i < count; i++)
+      if (arr[i].intersects (glyphs))
 	return true;
     return false;
   }
   bool intersects_coverage (const hb_set_t *glyphs, unsigned int index) const
   {
-    unsigned int i;
-    unsigned int count = rangeRecord.len;
-    for (i = 0; i < count; i++) {
-      const RangeRecord &range = rangeRecord[i];
+    /* TODO Rewrite as dagger. */
+    unsigned count = rangeRecord.len;
+    const RangeRecord *arr = rangeRecord.arrayZ;
+    for (unsigned i = 0; i < count; i++) {
+      const RangeRecord &range = arr[i];
       if (range.value <= index &&
 	  index < (unsigned int) range.value + (range.last - range.first) &&
 	  range.intersects (glyphs))
@@ -1815,8 +1819,13 @@ struct ClassDefFormat1
       if (hb_set_next (glyphs, &g)) return true;
       /* Fall through. */
     }
+    /* TODO Speed up, using set overlap first? */
+    /* TODO Rewrite as dagger. */
+    HBUINT16 k; /* TODO(constexpr) use constructor to initialize. */
+    k = klass;
+    const HBUINT16 *arr = classValue.arrayZ;
     for (unsigned int i = 0; i < count; i++)
-      if (classValue[i] == klass && glyphs->has (startGlyph + i))
+      if (arr[i] == k && glyphs->has (startGlyph + i))
 	return true;
     return false;
   }
@@ -1984,8 +1993,13 @@ struct ClassDefFormat2
 	return true;
       /* Fall through. */
     }
+    /* TODO Speed up, using set overlap first? */
+    /* TODO Rewrite as dagger. */
+    HBUINT16 k; /* TODO(constexpr) use constructor to initialize. */
+    k = klass;
+    const RangeRecord *arr = rangeRecord.arrayZ;
     for (unsigned int i = 0; i < count; i++)
-      if (rangeRecord[i].value == klass && rangeRecord[i].intersects (glyphs))
+      if (arr[i].value == k && arr[i].intersects (glyphs))
 	return true;
     return false;
   }