[gn build] Add a script checking if sources in BUILD.gn and CMakeList…

…s.txt files match.

Also fix a missing file in lib/Support/BUILD.gn found by the script.

The script is very stupid and assumes that CMakeLists.txt follow the standard
LLVM CMakeLists.txt formatting with one cpp source file per line. Despite its
simplicity, it works well in practice.

It would be nice if it also checked deps and maybe automatically applied its
suggestions.

Differential Revision: https://reviews.llvm.org/D54930

llvm-svn: 347925

llvm/utils/gn/README.rst

@@ -82,6 +82,24 @@ To not put `BUILD.gn` into the main tree, they are all below
 `utils/gn/secondary`.  For example, the build file for `llvm/lib/Support` is in
 `utils/gn/secondary/llvm/lib/Support`.
 
+.. _Syncing GN files from CMake files:
+
+Syncing GN files from CMake files
+=================================
+
+Sometimes after pulling in the latest changes, the GN build doesn't work.
+Most of the time this is due to someone adding a file to CMakeLists.txt file.
+Run `llvm/utils/gn/build/sync_source_lists_from_cmake.py` to print a report
+of which files need to be added to or removed from `BUILD.gn` files to
+match the corresponding `CMakeLists.txt`. You have to manually read the output
+of the script and implement its suggestions.
+
+If new `CMakeLists.txt` files have been added, you have to manually create
+a new corresponding `BUILD.gn` file below `llvm/utils/gn/secondary/`.
+
+If the dependencies in a `CMakeLists.txt` file have been changed, you have to
+manually analyze and fix.
+
 .. _Philosophy:
 
 Philosophy

llvm/utils/gn/build/sync_source_lists_from_cmake.py

@@ -0,0 +1,54 @@
+#!/usr/bin/env python
+
+"""Helps to keep BUILD.gn files in sync with the corresponding CMakeLists.txt.
+
+For each BUILD.gn file in the tree, checks if the list of cpp files in
+it is identical to the list of cpp files in the corresponding CMakeLists.txt
+file, and prints the difference if not."""
+
+from __future__ import print_function
+
+import os
+import re
+import subprocess
+
+def main():
+    gn_files = subprocess.check_output(
+            ['git', 'ls-files', '*BUILD.gn']).splitlines()
+
+    # Matches e.g. |   "foo.cpp",|.
+    gn_cpp_re = re.compile(r'^\s*"([^"]+\.(?:cpp|h))",$', re.MULTILINE)
+    # Matches e.g. |   "foo.cpp"|.
+    cmake_cpp_re = re.compile(r'^\s*([A-Za-z_0-9/-]+\.(?:cpp|h))$',
+                              re.MULTILINE)
+
+    for gn_file in gn_files:
+        # The CMakeLists.txt for llvm/utils/gn/secondary/foo/BUILD.gn is
+        # directly at foo/CMakeLists.txt.
+        strip_prefix = 'llvm/utils/gn/secondary/'
+        if not gn_file.startswith(strip_prefix):
+            continue
+        cmake_file = os.path.join(
+                os.path.dirname(gn_file[len(strip_prefix):]), 'CMakeLists.txt')
+        if not os.path.exists(cmake_file):
+            continue
+
+        def get_sources(source_re, text):
+            return set([m.group(1) for m in source_re.finditer(text)])
+        gn_cpp = get_sources(gn_cpp_re, open(gn_file).read())
+        cmake_cpp = get_sources(cmake_cpp_re, open(cmake_file).read())
+
+        if gn_cpp == cmake_cpp:
+            continue
+
+        print(gn_file)
+        add = cmake_cpp - gn_cpp
+        if add:
+            print('add:\n' + '\n'.join('    "%s",' % a for a in add))
+        remove = gn_cpp - cmake_cpp
+        if remove:
+            print('remove:\n' + '\n'.join(remove))
+        print()
+
+if __name__ == '__main__':
+    main()

llvm/utils/gn/secondary/llvm/lib/Support/BUILD.gn

@@ -39,6 +39,7 @@ static_library("Support") {
     "BinaryStreamWriter.cpp",
     "BlockFrequency.cpp",
     "BranchProbability.cpp",
+    "BuryPointer.cpp",
     "COM.cpp",
     "CachePruning.cpp",
     "Chrono.cpp",