Add logging verbosity level flag to extract_ir.py

This commit adds a logging verbosity level flag to extract_ir.py and the
appropriate plumbing/implementation in extract_ir_lib.py. This is
primarily motivated by these errors coming up quite often in non-trivial
builds (as it is fairly often there is some assembly or some flags don't
get passed around somewhere) and not providing a very high signal to
noise ratio, especially when used as a library against a bunch of
projects at once.

compiler_opt/tools/extract_ir.py

@@ -79,6 +79,12 @@
     'The section name passed to llvm-objcopy. For ELF object files, the '
     'default .llvmbc is correct. For Mach-O object files, one should use '
     '__LLVM,__bitcode')
+flags.DEFINE_enum(
+    'logging_verbosity', 'normal', ['quiet', 'normal', 'verbose'],
+    'The logging verbosity to use. Quiet does not log any failures, only '
+    'printing the status at the end. Normal prints failures as they occur. '
+    'Verbose prints failures as they occur along with detailed information '
+    'about the failure.')
 
 flags.mark_flag_as_required('output_dir')
 
@@ -89,6 +95,13 @@ def main(argv):
   if len(argv) > 1:
     raise app.UsageError('Too many command-line arguments.')
 
+  if (FLAGS.logging_verbosity == 'quiet'):
+    logging.set_verbosity(logging.ERROR)
+  elif (FLAGS.logging_verbosity == 'normal'):
+    logging.set_verbosity(logging.WARNING)
+  elif (FLAGS.logging_verbosity == 'verbose'):
+    logging.set_verbosity(logging.INFO)
+
   objs = []
   if FLAGS.input is not None and FLAGS.thinlto_build == 'local':
     raise ValueError('--thinlto_build=local cannot be run with --input')
@@ -128,6 +141,9 @@ def main(argv):
   extract_ir_lib.write_corpus_manifest(FLAGS.thinlto_build,
                                        relative_output_paths, FLAGS.output_dir)
 
+  # Reset logging verbosity so that we print status messages
+  logging.set_verbosity(logging.INFO)
+
   logging.info('Converted %d files out of %d',
                len(objs) - relative_output_paths.count(None), len(objs))
 

compiler_opt/tools/extract_ir_lib.py

@@ -135,9 +135,13 @@ def _extract_clang_artifacts(self, llvm_objcopy_path: str, cmd_filter: str,
       return None
     os.makedirs(self.dest_dir(), exist_ok=True)
     try:
+      subprocess_output = None if logging.get_verbosity(
+      ) == logging.INFO else subprocess.DEVNULL
       subprocess.run(
           self._get_extraction_cmd_command(llvm_objcopy_path, cmd_section_name),
-          check=True)
+          check=True,
+          stdout=subprocess_output,
+          stderr=subprocess_output)
       if cmd_filter is not None or is_thinlto:
         with open(self.cmd_file(), encoding='utf-8') as f:
           lines = f.readlines()