update_mir_test_checks: Improve the check for LLVM IR in MIR files

The LLVM IR section of a MIR document can start with "--- |" rather
than just "---", because "|" is a sigil for a freeform document in
YAML. We need to handle this so that we don't try to add check lines
to the LLVM IR functions in a MIR file.

llvm-svn: 323178

llvm/utils/update_mir_test_checks.py

@@ -360,7 +360,7 @@ def update_test_file(llc, test, remove_common_prefixes=False,
             if m:
                 state = 'ir function prefix'
                 func_name = m.group('func')
-            if input_line.strip() == '---':
+            if input_line.rstrip('| \r\n') == '---':
                 state = 'document'
             output_lines.append(input_line)
         elif state == 'document':