From 8c616a6efe7370e110d6a2f822bb1a38bf768ea6 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Mon, 9 May 2022 17:49:54 -0600
Subject: [PATCH 1/3] [cff] Allocate stack inline instead of using hb_vector_t

Speeds up glyph_extents and glyph_shape benchmarks for CFF by 10
to 16 percent!
---
 src/hb-cff-interp-common.hh | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/src/hb-cff-interp-common.hh b/src/hb-cff-interp-common.hh
index ab622a7a2..0b5ee3cc1 100644
--- a/src/hb-cff-interp-common.hh
+++ b/src/hb-cff-interp-common.hh
@@ -355,10 +355,8 @@ struct cff_stack_t
   {
     error = false;
     count = 0;
-    elements.init ();
-    elements.resize (kSizeLimit);
   }
-  void fini () { elements.fini (); }
+  void fini () {}
 
   ELEM& operator [] (unsigned int i)
   {
@@ -368,14 +366,14 @@ struct cff_stack_t
 
   void push (const ELEM &v)
   {
-    if (likely (count < elements.length))
+    if (likely (count < LIMIT))
       elements[count++] = v;
     else
       set_error ();
   }
   ELEM &push ()
   {
-    if (likely (count < elements.length))
+    if (likely (count < LIMIT))
       return elements[count++];
     else
     {
@@ -414,7 +412,7 @@ struct cff_stack_t
 
   void unpop ()
   {
-    if (likely (count < elements.length))
+    if (likely (count < LIMIT))
       count++;
     else
       set_error ();
@@ -422,18 +420,16 @@ struct cff_stack_t
 
   void clear () { count = 0; }
 
-  bool in_error () const { return (error || elements.in_error ()); }
+  bool in_error () const { return (error); }
   void set_error ()      { error = true; }
 
   unsigned int get_count () const { return count; }
   bool is_empty () const          { return !count; }
 
-  static constexpr unsigned kSizeLimit = LIMIT;
-
   protected:
   bool error;
   unsigned int count;
-  hb_vector_t<ELEM> elements;
+  ELEM elements[LIMIT];
 };
 
 /* argument stack */
@@ -489,7 +485,7 @@ struct arg_stack_t : cff_stack_t<ARG, 513>
   }
 
   hb_array_t<const ARG> get_subarray (unsigned int start) const
-  { return S::elements.sub_array (start); }
+  { return hb_array_t<const ARG> (S::elements).sub_array (start); }
 
   private:
   typedef cff_stack_t<ARG, 513> S;

From 6106ef8c0f61453c38c58f71a045481bf5546f2d Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Mon, 9 May 2022 18:12:09 -0600
Subject: [PATCH 2/3] [cff] Tighten up arg-stack access

---
 src/hb-cff-interp-common.hh | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/hb-cff-interp-common.hh b/src/hb-cff-interp-common.hh
index 0b5ee3cc1..bd23e74ad 100644
--- a/src/hb-cff-interp-common.hh
+++ b/src/hb-cff-interp-common.hh
@@ -360,7 +360,11 @@ struct cff_stack_t
 
   ELEM& operator [] (unsigned int i)
   {
-    if (unlikely (i >= count)) set_error ();
+    if (unlikely (i >= count))
+    {
+      set_error ();
+      return Crap (ELEM);
+    }
     return elements[i];
   }
 
@@ -426,7 +430,10 @@ struct cff_stack_t
   unsigned int get_count () const { return count; }
   bool is_empty () const          { return !count; }
 
-  protected:
+  hb_array_t<const ELEM> get_subarray (unsigned int start) const
+  { return hb_array_t<const ELEM> (elements).sub_array (start); }
+
+  private:
   bool error;
   unsigned int count;
   ELEM elements[LIMIT];
@@ -484,9 +491,6 @@ struct arg_stack_t : cff_stack_t<ARG, 513>
     return true;
   }
 
-  hb_array_t<const ARG> get_subarray (unsigned int start) const
-  { return hb_array_t<const ARG> (S::elements).sub_array (start); }
-
   private:
   typedef cff_stack_t<ARG, 513> S;
 };

From 1b14d2ff136a9f7522995393fda6f6644377657f Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Mon, 9 May 2022 18:15:31 -0600
Subject: [PATCH 3/3] [cff] Fix arg-stack peek() impl

---
 src/hb-cff-interp-common.hh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/hb-cff-interp-common.hh b/src/hb-cff-interp-common.hh
index bd23e74ad..2a9e60ffd 100644
--- a/src/hb-cff-interp-common.hh
+++ b/src/hb-cff-interp-common.hh
@@ -406,7 +406,7 @@ struct cff_stack_t
 
   const ELEM& peek ()
   {
-    if (unlikely (count < 0))
+    if (unlikely (count == 0))
     {
       set_error ();
       return Null (ELEM);