Remove internal settings.LTO in favor of options.lto (#27422)

Followup to #27407

Because `settings.LTO` was an internal setting not used anywhere in
JavaScript libraries or runtime code. This change removes `LTO` from
`src/settings_internal.js` and stores `-flto` / `-fno-lto` state in
`options.lto` on `EmccOptions` instead.

In the long run I hope to use internal settings only for values that
need to flow out the the JS compiler.

Author: sbc100

embuilder.py

@@ -21,6 +21,7 @@
 from contextlib import contextmanager
 
 from tools import cache, ports, shared, system_libs, utils
+from tools.cmdline import options
 from tools.settings import settings
 from tools.system_libs import USE_NINJA
 
@@ -232,7 +233,7 @@ def main():
   shared.check_sanity()
 
   if args.lto:
-    settings.LTO = args.lto
+    options.lto = args.lto
 
   if args.verbose:
     shared.PRINT_SUBPROCS = True

emcc.py

@@ -524,7 +524,7 @@ def get_clang_command_asm():
     return compiler + compile.get_target_flags()
 
   if state.mode == Mode.COMPILE_ONLY:
-    if options.output_file and get_file_suffix(options.output_file) == '.bc' and not settings.LTO and '-emit-llvm' not in state.orig_args:
+    if options.output_file and get_file_suffix(options.output_file) == '.bc' and not options.lto and '-emit-llvm' not in state.orig_args:
       diagnostics.warning('emcc', '.bc output file suffix used without -flto or -emit-llvm.  Consider using .o extension since emcc will output an object file, not a bitcode file')
     if all(get_file_suffix(i) in ASSEMBLY_EXTENSIONS for i in options.input_files):
       cmd = get_clang_command_asm() + newargs

src/settings_internal.js

@@ -152,8 +152,6 @@ var MINIFY_WASM_IMPORTED_MODULES = false;
 // Whether to minify exports from the Wasm module.
 var MINIFY_WASM_EXPORT_NAMES = true;
 
-// Internal: value of -flto argument (either full or thin)
-var LTO = 0;
 
 // Whether we may be accessing the address 2GB or higher. If so, then we need
 // to interpret incoming i32 pointers as unsigned.

test/test_other.py

@@ -102,6 +102,7 @@
 
 from tools import building, cache, response_file, shared, utils, webassembly
 from tools.building import get_building_env
+from tools.cmdline import options
 from tools.link import binary_encode
 from tools.settings import settings
 from tools.shared import (
@@ -753,7 +754,7 @@ def test_print_search_dirs(self, args):
     libpath = output.split('libraries: =', 1)[1].strip()
     libpath = libpath.split(os.pathsep)
     libpath = [Path(p) for p in libpath]
-    settings.LTO = '-flto' in args
+    options.lto = 'full' if '-flto' in args else None
     settings.MEMORY64 = int('-m64' in args)
     expected = cache.get_lib_dir(absolute=True)
     self.assertIn(expected, libpath)
@@ -768,7 +769,7 @@ def test_print_libgcc_file_name(self, args):
     output = self.run_process([EMCC, '-print-libgcc-file-name'] + args, stdout=PIPE).stdout
     output2 = self.run_process([EMCC, '--print-libgcc-file-name'] + args, stdout=PIPE).stdout
     self.assertEqual(output, output2)
-    settings.LTO = '-flto' in args
+    options.lto = 'full' if '-flto' in args else None
     settings.MEMORY64 = int('-m64' in args)
     libdir = cache.get_lib_dir(absolute=True)
     expected = os.path.join(libdir, 'libclang_rt.builtins.a')
@@ -805,7 +806,7 @@ def test_print_file_name(self, args):
     output2 = self.run_process([EMCC, '--print-file-name=libc.a'] + args, stdout=PIPE).stdout.rstrip()
     self.assertEqual(output, output2)
     filename = Path(output)
-    settings.LTO = '-flto' in args
+    options.lto = 'full' if '-flto' in args else None
     settings.MEMORY64 = int('-m64' in args)
     self.assertContained(cache.get_lib_name('libc.a'), str(filename))
 
@@ -11791,7 +11792,7 @@ def test_setjmp_emulated_casts(self):
     self.do_runf('src.c', 'ok\ndone\n', cflags=['-sEMULATE_FUNCTION_POINTER_CASTS'])
 
   def test_no_lto(self):
-    # This used to fail because settings.LTO didn't reflect `-fno-lto`.
+    # This used to fail because options.lto didn't reflect `-fno-lto`.
     # See bug https://github.com/emscripten-core/emscripten/issues/20308
     create_file('src.c', r'''
       #include <stdio.h>

tools/building.py

@@ -16,6 +16,7 @@
 
 from . import (
   cache,
+  cmdline,
   config,
   diagnostics,
   js_optimizer,
@@ -190,7 +191,7 @@ def lld_flags_for_executable(external_symbols):
       not settings.ASYNCIFY):
     cmd.append('--strip-debug')
 
-  if settings.LTO and not settings.EXIT_RUNTIME:
+  if cmdline.options.lto and not settings.EXIT_RUNTIME:
     # The WebAssembly backend can generate new references to `__cxa_atexit` at
     # LTO time.  This `-u` flag forces the `__cxa_atexit` symbol to be
     # included at LTO time.  For other such symbols we exclude them from LTO

tools/cache.py

@@ -110,6 +110,8 @@ def get_sysroot_dir(*parts):
 
 
 def get_lib_dir(absolute):
+  from .cmdline import options
+
   ensure_setup()
   path = Path(get_sysroot(absolute=absolute), 'lib')
   if settings.MEMORY64:
@@ -118,8 +120,8 @@ def get_lib_dir(absolute):
     path = Path(path, 'wasm32-emscripten')
   # if relevant, use a subdir of the cache
   subdir = []
-  if settings.LTO:
-    if settings.LTO == 'thin':
+  if options.lto:
+    if options.lto == 'thin':
       subdir.append('thinlto')
     else:
       subdir.append('lto')

tools/cmdline.py

@@ -73,6 +73,7 @@ class EmccOptions:
   input_language = None
   js_transform = None
   lib_dirs: list[str] = []
+  lto: str | None = None
   memory_profiler = False
   no_entry = False
   no_minify = False
@@ -315,11 +316,11 @@ def consume_arg_file():
       settings.OPT_LEVEL = level
     elif arg.startswith('-flto'):
       if '=' in arg:
-        settings.LTO = arg.split('=')[1]
+        options.lto = arg.split('=')[1]
       else:
-        settings.LTO = 'full'
+        options.lto = 'full'
     elif arg == "-fno-lto":
-      settings.LTO = 0
+      options.lto = None
     elif arg == "--save-temps":
       options.save_temps = True
     elif check_arg('--closure-args'):

tools/link.py

@@ -3111,7 +3111,7 @@ def package_files(target):
 
 @ToolchainProfiler.profile_block('calculate linker inputs')
 def phase_calculate_linker_inputs(linker_args):
-  using_lld = not (options.oformat == OFormat.OBJECT and settings.LTO)
+  using_lld = not (options.oformat == OFormat.OBJECT and options.lto)
 
   linker_args = filter_link_flags(linker_args, using_lld)
 

tools/system_libs.py

@@ -62,8 +62,8 @@ def get_base_cflags(build_dir, force_object_files=False, preprocess=True):
   # Always build system libraries with debug information.  Non-debug builds
   # will ignore this at link time because we link with `-strip-debug`.
   flags = ['-g', '-sSTRICT', '-Werror']
-  if settings.LTO and not force_object_files:
-    flags += ['-flto=' + settings.LTO]
+  if options.lto and not force_object_files:
+    flags += ['-flto=' + options.lto]
   if settings.MAIN_MODULE or settings.SIDE_MODULE:
     # Explicitly include `-sMAIN_MODULE` when building system libraries.
     # `-fPIC` alone is not enough to configure trigger the building and