LibC+Kernel: Prevent string functions from calling themselves

Most of the string.h and wchar.h functions are implemented quite naively
at the moment, and GCC's pattern recognition pass might realize what we
are trying to do, and transform them into libcalls. This is usually a
useful optimization, but not when we're implementing the functions
themselves :^)

Relevant discussion from the GCC Bugzilla:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102725

This prevents the infamous recursive `strlen`.

A more proper fix would be writing these functions in assembly. That
would likely give a small performance boost as well ;)

1 files changed, 6 insertions, 0 deletions

diff --git a/Userland/DynamicLoader/CMakeLists.txt b/Userland/DynamicLoader/CMakeLists.txt
index eaaf9b075e..55c86fc19e 100644
--- a/Userland/DynamicLoader/CMakeLists.txt
+++ b/Userland/DynamicLoader/CMakeLists.txt
@@ -36,6 +36,12 @@ set_source_files_properties (../Libraries/LibC/ssp.cpp PROPERTIES COMPILE_FLAGS
 # Prevent GCC from removing null checks by marking the `FILE*` argument non-null
 set_source_files_properties(../Libraries/LibC/stdio.cpp PROPERTIES COMPILE_FLAGS "-fno-builtin-fputc -fno-builtin-fputs -fno-builtin-fwrite")
 
+# Prevent naively implemented string functions (like strlen) from being "optimized" into a call to themselves.
+if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    set_source_files_properties(../Libraries/LibC/string.cpp ../Libraries/LibC/wchar.cpp
+        PROPERTIES COMPILE_FLAGS "-fno-tree-loop-distribution -fno-tree-loop-distribute-patterns")
+endif()
+
 add_executable(Loader.so ${SOURCES})
 
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")