From 4e406b07305007c84cef637f5753c196c34fac9c Mon Sep 17 00:00:00 2001
From: Gunnar Beutner <gbeutner@serenityos.org>
Date: Sun, 6 Nov 2022 07:57:23 +0100
Subject: [PATCH] Meta+LibUnicode: Avoid relocations for emoji data

Previously each emoji had its own symbol in the library which was then
referred to by another symbol. This caused thousands of avoidable data
relocations at load time.

This saves about 122kB RAM for each process which uses LibUnicode.
---
 .../LibUnicode/GenerateEmojiData.cpp          | 64 +++++++++++--------
 1 file changed, 39 insertions(+), 25 deletions(-)

diff --git a/Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateEmojiData.cpp b/Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateEmojiData.cpp
index c568682769..0722473ecd 100644
--- a/Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateEmojiData.cpp
+++ b/Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateEmojiData.cpp
@@ -25,9 +25,9 @@ struct Emoji {
     String subgroup;
     u32 display_order { 0 };
     Vector<u32> code_points;
-    String code_points_name;
     String encoded_code_points;
     String status;
+    size_t code_point_array_index { 0 };
 };
 
 struct EmojiData {
@@ -107,7 +107,6 @@ static ErrorOr<void> parse_emoji_test_data(Core::Stream::BufferedFile& file, Emo
 
         auto name = emoji_and_name.substring_view(emoji_and_name_spaces[2]).trim_whitespace();
         emoji.name = emoji_data.unique_strings.ensure(name.to_titlecase_string());
-        emoji.code_points_name = String::join('_', code_points);
         emoji.encoded_code_points = emoji_and_name.substring_view(0, emoji_and_name_spaces[1]).trim_whitespace();
         emoji.status = line.substring_view(*status_index + 1, *emoji_and_name_index - *status_index - 1).trim_whitespace();
 
@@ -161,7 +160,6 @@ static ErrorOr<void> parse_emoji_serenity_data(Core::Stream::BufferedFile& file,
             name = name.to_titlecase();
 
         emoji.name = emoji_data.unique_strings.ensure(move(name));
-        emoji.code_points_name = String::join('_', emoji.code_points);
         TRY(emoji_data.emojis.try_append(move(emoji)));
     }
 
@@ -199,6 +197,26 @@ namespace Unicode {
 
     emoji_data.unique_strings.generate(generator);
 
+    size_t total_code_point_count { 0 };
+    for (auto const& emoji : emoji_data.emojis) {
+        total_code_point_count += emoji.code_points.size();
+    }
+    generator.set("total_code_point_count", String::number(total_code_point_count));
+
+    generator.append(R"~~~(
+static constexpr Array<u32, @total_code_point_count@> s_emoji_code_points { {)~~~");
+
+    bool first = true;
+    for (auto const& emoji : emoji_data.emojis) {
+        for (auto code_point : emoji.code_points) {
+            generator.append(first ? " "sv : ", "sv);
+            generator.append(String::formatted("{:#x}", code_point));
+            first = false;
+        }
+    }
+
+    generator.append(" } };"sv);
+
     generator.append(R"~~~(
 struct EmojiData {
     constexpr Emoji to_unicode_emoji() const
@@ -207,35 +225,24 @@ struct EmojiData {
         emoji.name = decode_string(name);
         emoji.group = static_cast<EmojiGroup>(group);
         emoji.display_order = display_order;
-        emoji.code_points = code_points;
+        emoji.code_points = code_points();
 
         return emoji;
     }
 
+    constexpr Span<u32 const> code_points() const
+    {
+        return Span<u32 const>(s_emoji_code_points.data() + code_point_start, code_point_count);
+    }
+
     @string_index_type@ name { 0 };
     u8 group { 0 };
     u32 display_order { 0 };
-    Span<u32 const> code_points;
+    size_t code_point_start { 0 };
+    size_t code_point_count { 0 };
 };
 )~~~");
 
-    for (auto const& emoji : emoji_data.emojis) {
-        generator.set("name"sv, emoji.code_points_name);
-        generator.set("size"sv, String::number(emoji.code_points.size()));
-
-        generator.append(R"~~~(
-static constexpr Array<u32, @size@> s_@name@ { {)~~~");
-
-        bool first = true;
-        for (auto code_point : emoji.code_points) {
-            generator.append(first ? " "sv : ", "sv);
-            generator.append(String::formatted("{:#x}", code_point));
-            first = false;
-        }
-
-        generator.append(" } };"sv);
-    }
-
     generator.append(R"~~~(
 
 static constexpr Array<EmojiData, @emojis_size@> s_emojis { {)~~~");
@@ -244,10 +251,11 @@ static constexpr Array<EmojiData, @emojis_size@> s_emojis { {)~~~");
         generator.set("name"sv, String::number(emoji.name));
         generator.set("group"sv, String::number(to_underlying(emoji.group)));
         generator.set("display_order"sv, String::number(emoji.display_order));
-        generator.set("code_points_name"sv, emoji.code_points_name);
+        generator.set("code_point_start"sv, String::number(emoji.code_point_array_index));
+        generator.set("code_point_count"sv, String::number(emoji.code_points.size()));
 
         generator.append(R"~~~(
-    { @name@, @group@, @display_order@, s_@code_points_name@ },)~~~");
+    { @name@, @group@, @display_order@, @code_point_start@, @code_point_count@ },)~~~");
     }
 
     generator.append(R"~~~(
@@ -256,7 +264,7 @@ static constexpr Array<EmojiData, @emojis_size@> s_emojis { {)~~~");
 Optional<Emoji> find_emoji_for_code_points(Span<u32 const> code_points)
 {
     for (auto& emoji : s_emojis) {
-        if (emoji.code_points == code_points)
+        if (emoji.code_points() == code_points)
             return emoji.to_unicode_emoji();
     }
 
@@ -344,6 +352,12 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         TRY(parse_emoji_serenity_data(*emoji_serenity_file, emoji_data));
     }
 
+    size_t code_point_array_index { 0 };
+    for (auto& emoji : emoji_data.emojis) {
+        emoji.code_point_array_index = code_point_array_index;
+        code_point_array_index += emoji.code_points.size();
+    }
+
     if (!generated_header_path.is_empty()) {
         auto generated_header_file = TRY(open_file(generated_header_path, Core::Stream::OpenMode::Write));
         TRY(generate_emoji_data_header(*generated_header_file, emoji_data));