From 32dd9810cf156b7710bc849030d69b902e58077b Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 30 Nov 2022 13:15:58 -0700
Subject: [PATCH] [subset-cff1] Cache glyph-to-sid-map in the accelerator

Benchmark                                                                                      Time             CPU      Time Old      Time New       CPU Old       CPU New
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------
BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/nohinting/10                   -0.0841         -0.0843             0             0             0             0
BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/nohinting/64                   -0.1305         -0.1305             0             0             0             0
BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/nohinting/512                  -0.1398         -0.1401             1             1             1             1
BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/nohinting/4096                 +0.0382         +0.0380             9             9             9             9
BM_subset/subset_codepoints/SourceHanSans-Regular_subset.otf/nohinting/10000                +0.0213         +0.0211            11            11            11            11
---
 src/hb-ot-cff2-table.hh     |  5 +++++
 src/hb-subset-cff-common.hh |  2 ++
 src/hb-subset-cff1.cc       | 21 +++++++++++++++++----
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/src/hb-ot-cff2-table.hh b/src/hb-ot-cff2-table.hh
index e84709fa7..9081930bb 100644
--- a/src/hb-ot-cff2-table.hh
+++ b/src/hb-ot-cff2-table.hh
@@ -483,6 +483,11 @@ struct cff2
       blob = nullptr;
     }
 
+    hb_map_t *create_glyph_to_sid_map () const
+    {
+      return nullptr;
+    }
+
     bool is_valid () const { return blob; }
 
     protected:
diff --git a/src/hb-subset-cff-common.hh b/src/hb-subset-cff-common.hh
index a49f8d9f0..d724bd65e 100644
--- a/src/hb-subset-cff-common.hh
+++ b/src/hb-subset-cff-common.hh
@@ -433,11 +433,13 @@ struct cff_subset_accelerator_t
 
   ~cff_subset_accelerator_t() {
     hb_blob_destroy (original_blob);
+    hb_map_destroy (glyph_to_sid_map.get_relaxed ());
   }
 
   parsed_cs_str_vec_t parsed_charstrings;
   parsed_cs_str_vec_t parsed_global_subrs;
   hb_vector_t<parsed_cs_str_vec_t> parsed_local_subrs;
+  mutable hb_atomic_ptr_t<hb_map_t> glyph_to_sid_map = nullptr;
 
  private:
   hb_blob_t* original_blob;
diff --git a/src/hb-subset-cff1.cc b/src/hb-subset-cff1.cc
index fd169b21b..d46e102f2 100644
--- a/src/hb-subset-cff1.cc
+++ b/src/hb-subset-cff1.cc
@@ -443,8 +443,17 @@ struct cff_subset_plan {
       return;
     }
 
-    bool use_glyph_to_sid_map = plan->num_output_glyphs () > plan->source->get_num_glyphs () / 8.;
-    hb_map_t *glyph_to_sid_map = use_glyph_to_sid_map ? acc.create_glyph_to_sid_map () : nullptr;
+    hb_map_t *glyph_to_sid_map = (plan->accelerator && plan->accelerator->cff_accelerator) ?
+				  plan->accelerator->cff_accelerator->glyph_to_sid_map :
+				  nullptr;
+    bool created_map = false;
+    if (!glyph_to_sid_map &&
+	((plan->accelerator && plan->accelerator->cff_accelerator) ||
+	 plan->num_output_glyphs () > plan->source->get_num_glyphs () / 8.))
+    {
+      created_map = true;
+      glyph_to_sid_map = acc.create_glyph_to_sid_map ();
+    }
 
     unsigned int glyph;
     for (glyph = 1; glyph < plan->num_output_glyphs (); glyph++)
@@ -468,8 +477,12 @@ struct cff_subset_plan {
       last_sid = sid;
     }
 
-    if (glyph_to_sid_map)
-      hb_map_destroy (glyph_to_sid_map);
+    if (created_map)
+    {
+      if (!(plan->accelerator && plan->accelerator->cff_accelerator) ||
+	  !plan->accelerator->cff_accelerator->glyph_to_sid_map.cmpexch (nullptr, glyph_to_sid_map))
+	hb_map_destroy (glyph_to_sid_map);
+    }
 
     bool two_byte = subset_charset_ranges.complete (glyph);