llvm-build: Add initial --write-cmake-fragment option.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143744 91177308-0d34-0410-b5e6-96231b3b80d8

docs/CommandGuide/llvm-build.pod

@@ -48,6 +48,13 @@ component combinations.
 Write out new I<LLVMBuild.txt> files based on the loaded components. This is
 useful for auto-upgrading the schema of the files.
 
+=item B<--write-cmake-fragment>
+
+Write out the LLVMBuild in the form of a CMake fragment, so it can easily be
+consumed by the CMake based build system. The exact contents and format of this
+file are closely tied to how LLVMBuild is integrated with CMake, see LLVM's
+top-level CMakeLists.txt.
+
 =item B<--write-make-fragment>
 
 Write out the LLVMBuild in the form of a Makefile fragment, so it can easily be

utils/llvm-build/llvmbuild/main.py

@@ -286,22 +286,21 @@ class LLVMProjectInfo(object):
         print >>f, '};'
         f.close()
 
-    def write_make_fragment(self, output_path):
+    def get_fragment_dependencies(self):
         """
-        write_make_fragment(output_path) -> None
+        get_fragment_dependencies() -> iter
 
-        Generate a Makefile fragment which includes all of the collated
-        LLVMBuild information in a format that is easily digestible by a
-        Makefile. The exact contents of this are closely tied to how the LLVM
-        Makefiles integrate LLVMBuild, see Makefile.rules in the top-level.
+        Compute the list of files (as absolute paths) on which the output
+        fragments depend (i.e., files for which a modification should trigger a
+        rebuild of the fragment).
         """
 
         # Construct a list of all the dependencies of the Makefile fragment
         # itself. These include all the LLVMBuild files themselves, as well as
         # all of our own sources.
-        dependencies = []
         for ci in self.component_infos:
-            dependencies.append(os.path.join(self.source_root, ci.subpath[1:]))
+            yield os.path.join(self.source_root, ci.subpath[1:],
+                               'LLVMBuild.txt')
 
         # Gather the list of necessary sources by just finding all loaded
         # modules that are inside the LLVM source tree.
@@ -320,7 +319,77 @@ class LLVMProjectInfo(object):
             # If the path exists and is in the source tree, consider it a
             # dependency.
             if (path.startswith(self.source_root) and os.path.exists(path)):
-                dependencies.append(path)
+                yield path
+
+    def write_cmake_fragment(self, output_path):
+        """
+        write_cmake_fragment(output_path) -> None
+
+        Generate a CMake fragment which includes all of the collated LLVMBuild
+        information in a format that is easily digestible by a CMake. The exact
+        contents of this are closely tied to how the CMake configuration
+        integrates LLVMBuild, see CMakeLists.txt in the top-level.
+        """
+
+        dependencies = list(self.get_fragment_dependencies())
+
+        # Write out the CMake fragment.
+        f = open(output_path, 'w')
+
+        # Write the header.
+        header_fmt = '\
+#===-- %s - LLVMBuild Configuration for LLVM %s-*- CMake -*--===#'
+        header_name = os.path.basename(output_path)
+        header_pad = '-' * (80 - len(header_fmt % (header_name, '')))
+        header_string = header_fmt % (header_name, header_pad)
+        print >>f, """\
+%s
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+#===------------------------------------------------------------------------===#
+#
+# This file contains the LLVMBuild project information in a format easily
+# consumed by the CMake based build system.
+#
+# This file is autogenerated by llvm-build, do not edit!
+#
+#===------------------------------------------------------------------------===#
+""" % header_string
+
+        # Write the dependency information in the best way we can.
+        print >>f, """
+# LLVMBuild CMake fragment dependencies.
+#
+# CMake has no builtin way to declare that the configuration depends on
+# a particular file. However, a side effect of configure_file is to add
+# said input file to CMake's internal dependency list. So, we use that
+# and a dummy output file to communicate the dependency information to
+# CMake.
+#
+# FIXME: File a CMake RFE to get a properly supported version of this
+# feature."""
+        for dep in dependencies:
+            print >>f, """\
+configure_file(\"%s\"
+               ${CMAKE_CURRENT_BINARY_DIR}/DummyConfigureOutput)""" % (dep,)
+            
+        f.close()
+
+    def write_make_fragment(self, output_path):
+        """
+        write_make_fragment(output_path) -> None
+
+        Generate a Makefile fragment which includes all of the collated
+        LLVMBuild information in a format that is easily digestible by a
+        Makefile. The exact contents of this are closely tied to how the LLVM
+        Makefiles integrate LLVMBuild, see Makefile.rules in the top-level.
+        """
+
+        dependencies = list(self.get_fragment_dependencies())
 
         # Write out the Makefile fragment.
         f = open(output_path, 'w')
@@ -390,6 +459,10 @@ def main():
                       dest="write_library_table", metavar="PATH",
                       help="Write the C++ library dependency table to PATH",
                       action="store", default=None)
+    parser.add_option("", "--write-cmake-fragment",
+                      dest="write_cmake_fragment", metavar="PATH",
+                      help="Write the CMake project information to PATH",
+                      action="store", default=None)
     parser.add_option("", "--write-make-fragment",
                       dest="write_make_fragment", metavar="PATH",
                       help="Write the Makefile project information to PATH",
@@ -430,13 +503,17 @@ def main():
     if opts.write_llvmbuild:
         project_info.write_components(opts.write_llvmbuild)
 
-    # Write out the required librariy, if requested.
+    # Write out the required library table, if requested.
     if opts.write_library_table:
         project_info.write_library_table(opts.write_library_table)
 
-    # Write out the required librariy, if requested.
+    # Write out the make fragment, if requested.
     if opts.write_make_fragment:
         project_info.write_make_fragment(opts.write_make_fragment)
 
+    # Write out the cmake fragment, if requested.
+    if opts.write_cmake_fragment:
+        project_info.write_cmake_fragment(opts.write_cmake_fragment)
+
 if __name__=='__main__':
     main()