--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/utils/sort_includes.py	Mon May 25 11:07:02 2020 +0900
@@ -0,0 +1,93 @@
+#!/usr/bin/env python
+
+"""Script to sort the top-most block of #include lines.
+
+Assumes the LLVM coding conventions.
+
+Currently, this script only bothers sorting the llvm/... headers. Patches
+welcome for more functionality, and sorting other header groups.
+"""
+
+import argparse
+import os
+
+def sort_includes(f):
+  """Sort the #include lines of a specific file."""
+
+  # Skip files which are under INPUTS trees or test trees.
+  if 'INPUTS/' in f.name or 'test/' in f.name:
+    return
+
+  ext = os.path.splitext(f.name)[1]
+  if ext not in ['.cpp', '.c', '.h', '.inc', '.def']:
+    return
+
+  lines = f.readlines()
+  look_for_api_header = ext in ['.cpp', '.c']
+  found_headers = False
+  headers_begin = 0
+  headers_end = 0
+  api_headers = []
+  local_headers = []
+  subproject_headers = []
+  llvm_headers = []
+  system_headers = []
+  for (i, l) in enumerate(lines):
+    if l.strip() == '':
+      continue
+    if l.startswith('#include'):
+      if not found_headers:
+        headers_begin = i
+        found_headers = True
+      headers_end = i
+      header = l[len('#include'):].lstrip()
+      if look_for_api_header and header.startswith('"'):
+        api_headers.append(header)
+        look_for_api_header = False
+        continue
+      if (header.startswith('<') or header.startswith('"gtest/') or
+          header.startswith('"isl/') or header.startswith('"json/')):
+        system_headers.append(header)
+        continue
+      if (header.startswith('"clang/') or header.startswith('"clang-c/') or
+          header.startswith('"polly/')):
+        subproject_headers.append(header)
+        continue
+      if (header.startswith('"llvm/') or header.startswith('"llvm-c/')):
+        llvm_headers.append(header)
+        continue
+      local_headers.append(header)
+      continue
+
+    # Only allow comments and #defines prior to any includes. If either are
+    # mixed with includes, the order might be sensitive.
+    if found_headers:
+      break
+    if l.startswith('//') or l.startswith('#define') or l.startswith('#ifndef'):
+      continue
+    break
+  if not found_headers:
+    return
+
+  local_headers = sorted(set(local_headers))
+  subproject_headers = sorted(set(subproject_headers))
+  llvm_headers = sorted(set(llvm_headers))
+  system_headers = sorted(set(system_headers))
+  headers = api_headers + local_headers + subproject_headers + llvm_headers + system_headers
+  header_lines = ['#include ' + h for h in headers]
+  lines = lines[:headers_begin] + header_lines + lines[headers_end + 1:]
+
+  f.seek(0)
+  f.truncate()
+  f.writelines(lines)
+
+def main():
+  parser = argparse.ArgumentParser(description=__doc__)
+  parser.add_argument('files', nargs='+', type=argparse.FileType('r+'),
+                      help='the source files to sort includes within')
+  args = parser.parse_args()
+  for f in args.files:
+    sort_includes(f)
+
+if __name__ == '__main__':
+  main()