1 files changed, 109 insertions, 0 deletions
diff --git a/llvm/utils/gn/build/write_cmake_config.py b/llvm/utils/gn/build/write_cmake_config.py
new file mode 100644
index 00000000000..408ffcdbfc0
--- /dev/null
+++ b/llvm/utils/gn/build/write_cmake_config.py
@@ -0,0 +1,109 @@
+"""Processes a foo.h.cmake file and writes foo.h.
+
+Takes a list of KEY=VALUE pairs (where VALUE can be empty).
+
+Handles these types of lines (note that FOO= sets the value of FOO to the empty
+string, which is falsy, but FOO=0 sets it to '0' which is truthy):
+
+1.) #cmakedefine01 FOO
+    Checks if key FOO is set to a truthy value, and depending on that prints
+    one of the following two lines:
+
+        #define FOO 1
+        #define FOO 0
+
+2.) #cmakedefine FOO
+    Checks if key FOO is set to a truthy in value, and depending on that prints
+    one of the following two lines:
+
+        #define FOO
+        /* #undef FOO */
+
+3.) #cmakedefine FOO asdf${BAR}jkl
+    Checks if key FOO is set to a truthy values, and if so replaces all
+    variable references in `asdf${BAR}jkl` with their value and prints that
+    (else it prints the same undef line as the previous form):
+
+        #define FOO asdfBAR_VALjkl
+        /* #undef FOO */
+
+4.) #define FOO asdf{BAR}jkl
+    Always gets its variable values filled in, independent of FOO's value being
+    set:
+
+        #define FOO asdfBAR_VALjkl
+
+Fails if any of the KEY=VALUE arguments aren't needed for processing the
+.h.cmake file, or if the .h.cmake file has unreplaces ${VAR} references after
+processing all values.
+"""
+
+import argparse
+import os
+import re
+import sys
+
+
+def main():
+    parser = argparse.ArgumentParser(
+                 epilog=__doc__,
+                 formatter_class=argparse.RawDescriptionHelpFormatter)
+    parser.add_argument('input', help='input file')
+    parser.add_argument('values', nargs='*', help='several KEY=VALUE pairs')
+    parser.add_argument('-o', '--output', required=True,
+                        help='output file')
+    args = parser.parse_args()
+
+    values = {}
+    for value in args.values:
+        key, val = value.split('=', 1)
+        values[key] = val
+    unused_values = set(values.keys())
+
+    # Matches e.g. '${CLANG_FOO}' and captures CLANG_FOO in group 1.
+    var_re = re.compile(r'\$\{([^}]*)\}')
+
+    in_lines = open(args.input).readlines()
+    out_lines = []
+    for in_line in in_lines:
+        def repl(m):
+            unused_values.discard(m.group(1))
+            return values[m.group(1)]
+        if in_line.startswith('#cmakedefine01 '):
+            _, var = in_line.split()
+            out_lines.append('#define %s %d\n' % (var, 1 if values[var] else 0))
+            unused_values.discard(var)
+        elif in_line.startswith('#cmakedefine '):
+            _, var = in_line.split(None, 1)
+            try:
+                var, val = var.split(None, 1)
+            except:
+                var, val = var.rstrip(), '\n'
+            if values[var]:
+                out_lines.append('#define %s %s' % (var,
+                                                    var_re.sub(repl, val)))
+            else:
+                out_lines.append('/* #undef %s */\n' % var)
+            unused_values.discard(var)
+        else:
+            # In particular, handles `#define FOO ${FOO}` lines.
+            out_lines.append(var_re.sub(repl, in_line))
+
+    if unused_values:
+        print >>sys.stderr, 'Unused --values args:'
+        print >>sys.stderr, '    ', '\n    '.join(unused_values)
+        return 1
+
+    output = ''.join(out_lines)
+
+    leftovers = var_re.findall(output)
+    if leftovers:
+        print >>sys.stderr, 'unprocessed values:\n', '\n'.join(leftovers)
+        return 1
+
+    if not os.path.exists(args.output) or open(args.output).read() != output:
+        open(args.output, 'w').write(output)
+
+
+if __name__ == '__main__':
+    sys.exit(main())