From 96f51f09d4ecc034ad5c3b4afa6887b0e18c1b65 Mon Sep 17 00:00:00 2001
From: Greg Bedwell <greg_bedwell@sn.scee.net>
Date: Mon, 4 Jun 2018 12:30:10 +0000
Subject: [PATCH] [llvm-mca][UpdateTestChecks] Prevent an IndexError being
 raised when given empty input

llvm-svn: 333894
---
 llvm/utils/update_mca_test_checks.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/utils/update_mca_test_checks.py b/llvm/utils/update_mca_test_checks.py
index f99ca343f96b..dcd52f6e913c 100755
--- a/llvm/utils/update_mca_test_checks.py
+++ b/llvm/utils/update_mca_test_checks.py
@@ -409,7 +409,7 @@ def _write_output(test_path, input_lines, prefix_list, block_infos,  # noqa
       continue
 
   # Add a blank line before the new checks if required.
-  if output_lines[-1]:
+  if len(output_lines) > 0 and output_lines[-1]:
     output_lines.append('')
 
   output_check_lines = []