From e333223f269a090732ae3a9d468bb93c35bbeb62 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 25 Nov 2022 14:23:57 -0700
Subject: [PATCH] [array] Optimize serializing copy()

---
 src/hb-array.hh  | 16 +++++++++++++++-
 src/hb-vector.hh | 11 ++++++-----
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/src/hb-array.hh b/src/hb-array.hh
index 18bcd5225..5cadc4805 100644
--- a/src/hb-array.hh
+++ b/src/hb-array.hh
@@ -262,7 +262,9 @@ struct hb_array_t : hb_iter_with_fallback_t<hb_array_t<Type>, Type&>
   void fini ()
   { hb_free ((void *) arrayZ); arrayZ = nullptr; length = 0; }
 
-  template <typename hb_serialize_context_t>
+  template <typename hb_serialize_context_t,
+	    typename U = Type,
+	    hb_enable_if (!(sizeof (U) < sizeof (long long) && hb_is_trivially_copy_assignable(Type)))>
   hb_array_t copy (hb_serialize_context_t *c) const
   {
     TRACE_SERIALIZE (this);
@@ -273,6 +275,18 @@ struct hb_array_t : hb_iter_with_fallback_t<hb_array_t<Type>, Type&>
     return_trace (hb_array_t (out, length));
   }
 
+  template <typename hb_serialize_context_t,
+	    typename U = Type,
+	    hb_enable_if (sizeof (U) < sizeof (long long) && hb_is_trivially_copy_assignable(Type))>
+  hb_array_t copy (hb_serialize_context_t *c) const
+  {
+    TRACE_SERIALIZE (this);
+    auto* out = c->start_embed (arrayZ);
+    if (unlikely (!c->extend_size (out, get_size ()))) return_trace (hb_array_t ());
+    hb_memcpy (out, arrayZ, length);
+    return_trace (hb_array_t (out, length));
+  }
+
   template <typename hb_sanitize_context_t>
   bool sanitize (hb_sanitize_context_t *c) const
   { return c->check_array (arrayZ, length); }
diff --git a/src/hb-vector.hh b/src/hb-vector.hh
index 5a82aa61b..e6bb7d22e 100644
--- a/src/hb-vector.hh
+++ b/src/hb-vector.hh
@@ -268,12 +268,13 @@ struct hb_vector_t
   {
     length = other.length;
 #ifndef HB_OPTIMIZE_SIZE
-    /* This runs faster because of alignment. */
-    for (unsigned i = 0; i < length; i++)
-      arrayZ[i] = other.arrayZ[i];
-#else
-     hb_memcpy ((void *) arrayZ, (const void *) other.arrayZ, length * item_size);
+    if (sizeof (T) >= sizeof (long long))
+      /* This runs faster because of alignment. */
+      for (unsigned i = 0; i < length; i++)
+	arrayZ[i] = other.arrayZ[i];
+    else
 #endif
+       hb_memcpy ((void *) arrayZ, (const void *) other.arrayZ, length * item_size);
   }
   template <typename T = Type,
 	    hb_enable_if (!hb_is_trivially_copyable (T) &&