From 3edd6cdcd55dabec87ed8da9ffed82b1c41e0720 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Tue, 27 Jun 2023 06:56:00 -0600
Subject: [PATCH] [vector] Minor micro-optimize shrink_vector

The compiler seems to understand this pattern better.
---
 src/hb-vector.hh | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/hb-vector.hh b/src/hb-vector.hh
index 8e11d65ee..23a96d708 100644
--- a/src/hb-vector.hh
+++ b/src/hb-vector.hh
@@ -374,14 +374,15 @@ struct hb_vector_t
   void
   shrink_vector (unsigned size)
   {
-    if (std::is_trivially_destructible<Type>::value)
-      length = size;
-    else
-      while ((unsigned) length > size)
-      {
-	arrayZ[(unsigned) length - 1].~Type ();
-	length--;
-      }
+    assert (size <= length);
+    if (!std::is_trivially_destructible<Type>::value)
+    {
+      unsigned count = length - size;
+      Type *p = arrayZ + length - 1;
+      while (count--)
+        p--->~Type ();
+    }
+    length = size;
   }
 
   void