import the already imported part of llvm-libc from HEAD

Author: google-yfyang

system/lib/llvm-libc/readme.txt

@@ -1,7 +1,7 @@
 llvm's libc
 -----------
 
-These files are from llvm-project based on release 20.1.4.
+These files are from llvm-project's HEAD.
 
 We maintain a local fork of llvm-project that contains any emscripten
 specific patches:
@@ -10,18 +10,23 @@ specific patches:
 
 The current patch is based on the emscripten-libs-20 branch.
 
-We do not use LLVM's libc directly, but libcxx uses a subset of headers from
-libc. So we only import these directories that libcxx depend on:
+Currently in producgtion, we do not use LLVM's libc directly yet, but libcxx uses a subset 
+of headers from libc. So libcxx directly depends on the following directories:
 - libc/hdr
 - libc/include/llvm-libc-macros
 - libc/include/llvm-libc-types
 - libc/shared
 - libc/src/__support
 
+In addition, we are experimenting with using llvm-libc in overlay mode. You can enable this
+by running with `EMCC_CFLAGS=-lllvmlibc`. See https://libc.llvm.org/overlay_mode.html for more
+details.
+
 Update Instructions
 -------------------
 
 Run `system/lib/update_libcxx.py path/to/llvm-project`
+Run `system/lib/update_llvm_libc.py path/to/llvm-project`
 
 Modifications
 -------------

system/lib/update_libcxx.py

@@ -25,14 +25,6 @@
     'include/llvm-libc-types',
     'shared',
     'config',
-    'src/__support',
-    'src/string',
-    'src/strings',
-    'src/errno',
-    'src/math',
-    'src/stdlib',
-    'src/inttypes',
-    'src/stdio/printf_core',
 ]
 
 def clean_dir(dirname):

system/lib/update_llvm_libc.py

@@ -8,12 +8,10 @@
 import sys
 import shutil
 import glob
-import subprocess
 
 script_dir = os.path.abspath(os.path.dirname(__file__))
 emscripten_root = os.path.dirname(os.path.dirname(script_dir))
 default_llvm_dir = os.path.join(os.path.dirname(emscripten_root), 'llvm-project')
-emscripten_patches = os.path.join(script_dir, "llvm-libc", "patches", "*.patch")
 
 preserve_files = ('readme.txt', '__assertion_handler', '__config_site')
 # ryu_long_double_constants.h from libc is unused (and very large)
@@ -68,30 +66,13 @@ def copy_tree(upstream_dir, local_dir):
         full = os.path.join(root, f)
         os.remove(full)
 
-def apply_patch(patch_file):
-  try:
-    command = ["git", "apply", "-p2", "--directory=system/lib/llvm-libc/", patch_file]
-
-    result = subprocess.run(
-        command,
-        capture_output=True,
-        text=True,
-        check=True
-    )
-
-  except subprocess.CalledProcessError as e:
-    print(f"Error applying patch: {e}")
-    print("STDOUT:", e.stdout)
-    print("STDERR:", e.stderr)
-
 def main():
   if len(sys.argv) > 1:
     llvm_dir = os.path.abspath(sys.argv[1])
   else:
     llvm_dir = default_llvm_dir
   libcxx_dir = os.path.join(llvm_dir, 'libcxx')
 
-  # libcxx includes headers from LLVM's libc
   libc_upstream_dir = os.path.join(llvm_dir, 'libc')
   assert os.path.exists(libc_upstream_dir)
   libc_local_dir = os.path.join(script_dir, 'llvm-libc')
@@ -111,9 +92,5 @@ def main():
     for file in files_to_exclude:
         os.remove(file)
 
-  patches_to_apply = glob.glob(emscripten_patches)
-  for patch in patches_to_apply:
-    apply_patch(patch)
-
 if __name__ == '__main__':
   main()