[libc] Remove common_libc_tuners.cmake and move options into config.j…

…son. (#66226)

The name has been changed to adhere to the config option naming format.
The necessary build changes to use the new option have also been made.

libc/CMakeLists.txt

@@ -64,8 +64,6 @@ add_compile_definitions(LIBC_NAMESPACE=${LIBC_NAMESPACE})
 # Flags to pass down to the compiler while building the libc functions.
 set(LIBC_COMPILE_OPTIONS_DEFAULT "" CACHE STRING "Architecture to tell clang to optimize for (e.g. -march=... or -mcpu=...)")
 
-include(common_libc_tuners.cmake)
-
 list(APPEND LIBC_COMPILE_OPTIONS_DEFAULT ${LIBC_COMMON_TUNE_OPTIONS})
 
 # Check --print-resource-dir to find the compiler resource dir if this flag

libc/cmake/modules/LLVMLibCObjectRules.cmake

@@ -672,6 +672,7 @@ function(create_entrypoint_object fq_target_name)
     target_compile_options(${internal_target_name} BEFORE PRIVATE ${common_compile_options})
     target_include_directories(${internal_target_name} PRIVATE ${include_dirs})
     add_dependencies(${internal_target_name} ${full_deps_list})
+    target_link_libraries(${internal_target_name} ${full_deps_list})
 
     add_library(
       ${fq_target_name}
@@ -685,6 +686,7 @@ function(create_entrypoint_object fq_target_name)
     target_compile_options(${fq_target_name} BEFORE PRIVATE ${common_compile_options} -DLIBC_COPT_PUBLIC_PACKAGING)
     target_include_directories(${fq_target_name} PRIVATE ${include_dirs})
     add_dependencies(${fq_target_name} ${full_deps_list})
+    target_link_libraries(${fq_target_name} ${full_deps_list})
   endif()
 
   set_target_properties(

libc/config/config.json

@@ -16,5 +16,11 @@
       "value": true,
       "doc": "Use large table for better printf long double performance."
     }
+  },
+  "string": {
+    "LIBC_CONF_STRING_UNSAFE_WIDE_READ": {
+      "value": false,
+      "doc": "Read more than a byte at a time to perform byte-string operations like strlen."
+    }
   }
 }

libc/docs/configure.rst

@@ -30,3 +30,5 @@ to learn about the defaults for your platform and target.
     - ``LIBC_CONF_PRINTF_DISABLE_INDEX_MODE``: Disable index mode in the printf format string.
     - ``LIBC_CONF_PRINTF_DISABLE_WRITE_INT``: Disable handling of %n in printf format string.
     - ``LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_MEGA_LONG_DOUBLE_TABLE``: Use large table for better printf long double performance.
+* **"string" options**
+    - ``LIBC_CONF_STRING_UNSAFE_WIDE_READ``: Read more than a byte at a time to perform byte-string operations like strlen.

libc/src/string/CMakeLists.txt

@@ -1,5 +1,12 @@
 add_subdirectory(memory_utils)
 
+if(LIBC_CONF_STRING_UNSAFE_WIDE_READ)
+  list(APPEND string_config_options "-DLIBC_COPT_STRING_UNSAFE_WIDE_READ")
+endif()
+if(string_config_options)
+  list(PREPEND string_config_options "COMPILE_OPTIONS")
+endif()
+
 add_header_library(
   string_utils
   HDRS
@@ -10,6 +17,7 @@ add_header_library(
     libc.include.stdlib
     libc.src.__support.common
     libc.src.__support.CPP.bitset
+  ${string_config_options}
 )
 
 add_header_library(

libc/src/string/string_utils.h

@@ -88,7 +88,7 @@ LIBC_INLINE size_t string_length_byte_read(const char *src) {
 // Returns the length of a string, denoted by the first occurrence
 // of a null terminator.
 LIBC_INLINE size_t string_length(const char *src) {
-#ifdef LIBC_COPT_UNSAFE_STRING_WIDE_READ
+#ifdef LIBC_COPT_STRING_UNSAFE_WIDE_READ
   // Unsigned int is the default size for most processors, and on x86-64 it
   // performs better than larger sizes when the src pointer can't be assumed to
   // be aligned to a word boundary, so it's the size we use for reading the
@@ -143,7 +143,7 @@ LIBC_INLINE void *find_first_character_byte_read(const unsigned char *src,
 // 'src'. If 'ch' is not found, returns nullptr.
 LIBC_INLINE void *find_first_character(const unsigned char *src,
                                        unsigned char ch, size_t max_strlen) {
-#ifdef LIBC_COPT_UNSAFE_STRING_WIDE_READ
+#ifdef LIBC_COPT_STRING_UNSAFE_WIDE_READ
   // If the maximum size of the string is small, the overhead of aligning to a
   // word boundary and generating a bitmask of the appropriate size may be
   // greater than the gains from reading larger chunks. Based on some testing,