1 files changed, 48 insertions, 10 deletions
diff --git a/utils/google-benchmark/tools/compare_bench.py b/utils/google-benchmark/tools/compare_bench.py
index ed0f133e0dc9..d54baaa0e8f8 100644
--- a/utils/google-benchmark/tools/compare_bench.py
+++ b/utils/google-benchmark/tools/compare_bench.py
@@ -3,25 +3,63 @@
 compare_bench.py - Compare two benchmarks or their results and report the
                    difference.
 """
+import argparse
+from argparse import ArgumentParser
 import sys
 import gbench
 from gbench import util, report
+from gbench.util import *
+
+def check_inputs(in1, in2, flags):
+    """
+    Perform checking on the user provided inputs and diagnose any abnormalities
+    """
+    in1_kind, in1_err = classify_input_file(in1)
+    in2_kind, in2_err = classify_input_file(in2)
+    output_file = find_benchmark_flag('--benchmark_out=', flags)
+    output_type = find_benchmark_flag('--benchmark_out_format=', flags)
+    if in1_kind == IT_Executable and in2_kind == IT_Executable and output_file:
+        print(("WARNING: '--benchmark_out=%s' will be passed to both "
+              "benchmarks causing it to be overwritten") % output_file)
+    if in1_kind == IT_JSON and in2_kind == IT_JSON and len(flags) > 0:
+        print("WARNING: passing --benchmark flags has no effect since both "
+              "inputs are JSON")
+    if output_type is not None and output_type != 'json':
+        print(("ERROR: passing '--benchmark_out_format=%s' to 'compare_bench.py`"
+              " is not supported.") % output_type)
+        sys.exit(1)
+
 
 def main():
+    parser = ArgumentParser(
+        description='compare the results of two benchmarks')
+    parser.add_argument(
+        'test1', metavar='test1', type=str, nargs=1,
+        help='A benchmark executable or JSON output file')
+    parser.add_argument(
+        'test2', metavar='test2', type=str, nargs=1,
+        help='A benchmark executable or JSON output file')
+    # FIXME this is a dummy argument which will never actually match
+    # any --benchmark flags but it helps generate a better usage message
+    parser.add_argument(
+        'benchmark_options', metavar='benchmark_option', nargs='*',
+        help='Arguments to pass when running benchmark executables'
+    )
+    args, unknown_args = parser.parse_known_args()
     # Parse the command line flags
-    def usage():
-        print('compare_bench.py <test1> <test2> [benchmark options]...')
+    test1 = args.test1[0]
+    test2 = args.test2[0]
+    if args.benchmark_options:
+        print("Unrecognized positional argument arguments: '%s'"
+              % args.benchmark_options)
         exit(1)
-    if '--help' in sys.argv or len(sys.argv) < 3:
-        usage()
-    tests = sys.argv[1:3]
-    bench_opts = sys.argv[3:]
-    bench_opts = list(bench_opts)
+    benchmark_options = unknown_args
+    check_inputs(test1, test2, benchmark_options)
     # Run the benchmarks and report the results
-    json1 = gbench.util.run_or_load_benchmark(tests[0], bench_opts)
-    json2 = gbench.util.run_or_load_benchmark(tests[1], bench_opts)
+    json1 = gbench.util.run_or_load_benchmark(test1, benchmark_options)
+    json2 = gbench.util.run_or_load_benchmark(test2, benchmark_options)
     output_lines = gbench.report.generate_difference_report(json1, json2)
-    print 'Comparing %s to %s' % (tests[0], tests[1])
+    print('Comparing %s to %s' % (test1, test2))
     for ln in output_lines:
         print(ln)