From 2947ae7d6e13fee8a63fbf5cb14a79878e2f2700 Mon Sep 17 00:00:00 2001
From: Ali Mohammad Pur <ali.mpfard@gmail.com>
Date: Tue, 24 Jun 2025 15:48:33 +0200
Subject: [PATCH] LibRegex: Move required bytecode.flatten() outside
 optimization function

Not running the optimization passes should not leave the bytecode in a
broken state. Fixes #5146.
---
 Libraries/LibRegex/RegexMatcher.cpp   | 2 ++
 Libraries/LibRegex/RegexOptimizer.cpp | 2 --
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Libraries/LibRegex/RegexMatcher.cpp b/Libraries/LibRegex/RegexMatcher.cpp
index dc4486d6a5f..972dda82247 100644
--- a/Libraries/LibRegex/RegexMatcher.cpp
+++ b/Libraries/LibRegex/RegexMatcher.cpp
@@ -74,6 +74,7 @@ Regex<Parser>::Regex(ByteString pattern, typename ParserTraits<Parser>::OptionsT
 
         Parser parser(lexer, regex_options);
         parser_result = parser.parse();
+        parser_result.bytecode.flatten();
 
         run_optimization_passes();
 
@@ -90,6 +91,7 @@ Regex<Parser>::Regex(regex::Parser::Result parse_result, ByteString pattern, typ
     : pattern_value(move(pattern))
     , parser_result(move(parse_result))
 {
+    parser_result.bytecode.flatten();
     run_optimization_passes();
     if (parser_result.error == regex::Error::NoError)
         matcher = make<Matcher<Parser>>(this, regex_options | static_cast<decltype(regex_options.value())>(parser_result.options.value()));
diff --git a/Libraries/LibRegex/RegexOptimizer.cpp b/Libraries/LibRegex/RegexOptimizer.cpp
index 472f23d6a67..8e8161a997e 100644
--- a/Libraries/LibRegex/RegexOptimizer.cpp
+++ b/Libraries/LibRegex/RegexOptimizer.cpp
@@ -28,8 +28,6 @@ using Detail::Block;
 template<typename Parser>
 void Regex<Parser>::run_optimization_passes()
 {
-    parser_result.bytecode.flatten();
-
     rewrite_with_useless_jumps_removed();
 
     auto blocks = split_basic_blocks(parser_result.bytecode);