From ba379cba52974285414ffac16faa752f16ea9a28 Mon Sep 17 00:00:00 2001
From: Maxime Coste <mawww@kakoune.org>
Date: Thu, 30 Jul 2020 19:51:25 +1000
Subject: [PATCH] Micro-optimize regex character class/type matching

Also force-inline step_thread as function call overhead has a
mesurable impact.
---
 src/regex_impl.cc | 27 ++++++++++++---------------
 src/regex_impl.hh |  1 +
 2 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/src/regex_impl.cc b/src/regex_impl.cc
index ff65cdbe..5507273c 100644
--- a/src/regex_impl.cc
+++ b/src/regex_impl.cc
@@ -1173,27 +1173,24 @@ bool is_character_class(const CharacterClass& character_class, Codepoint cp)
     if (character_class.ignore_case)
         cp = to_lower(cp);
 
-    auto it = std::lower_bound(character_class.ranges.begin(),
-                               character_class.ranges.end(), cp,
-                               [](auto& range, Codepoint cp)
-                               { return range.max < cp; });
-
-    auto found = (it != character_class.ranges.end() and it->min <= cp) or
-                 is_ctype(character_class.ctypes, cp);
+    auto it = std::find_if(character_class.ranges.begin(),
+                           character_class.ranges.end(),
+                           [cp](auto& range) { return range.min <= cp and cp <= range.max; });
 
+    bool found = it != character_class.ranges.end() or (character_class.ctypes != CharacterType::None and
+                                                        is_ctype(character_class.ctypes, cp));
     return found != character_class.negative;
 }
 
 bool is_ctype(CharacterType ctype, Codepoint cp)
 {
-    return ((ctype & CharacterType::Whitespace)              and     is_blank(cp))            or
-           ((ctype & CharacterType::HorizontalWhitespace)    and     is_horizontal_blank(cp)) or
-           ((ctype & CharacterType::Digit)                   and     iswdigit(cp))            or
-           ((ctype & CharacterType::Word)                    and     is_word(cp))             or
-           ((ctype & CharacterType::NotWhitespace)           and not is_blank(cp))            or
-           ((ctype & CharacterType::NotHorizontalWhitespace) and not is_horizontal_blank(cp)) or
-           ((ctype & CharacterType::NotDigit)                and not iswdigit(cp))            or
-           ((ctype & CharacterType::NotWord)                 and not is_word(cp));
+    auto check = [&](CharacterType bit, CharacterType not_bit, auto&& func) {
+        return (ctype & (bit | not_bit)) and func(cp) == (bool)(ctype & bit);
+    };
+    return check(CharacterType::Word, CharacterType::NotWord, [](Codepoint cp) { return is_word(cp); }) or
+           check(CharacterType::Whitespace, CharacterType::NotWhitespace, is_blank) or
+           check(CharacterType::HorizontalWhitespace, CharacterType::NotHorizontalWhitespace, is_horizontal_blank) or
+           check(CharacterType::Digit, CharacterType::NotDigit, iswdigit);
 }
 
 namespace
diff --git a/src/regex_impl.hh b/src/regex_impl.hh
index db64c758..0565c49c 100644
--- a/src/regex_impl.hh
+++ b/src/regex_impl.hh
@@ -338,6 +338,7 @@ private:
     };
 
     // Steps a thread until it consumes the current character, matches or fail
+    [[gnu::always_inline]]
     void step_thread(const Iterator& pos, uint16_t current_step, Thread thread, const ExecConfig& config)
     {
         auto failed = [this, &thread]() {