Fix build-script -B

Without additional options, build-script -B was badly broken:
* It added a broken --independent-samples option to the driver command line
* Slow tests that ran only 1 sample by default would break the statistics

Fix the first issue by adding `--independent-samples` to the command
line only when a sample was actually provided by other options.

Fix the second issue by including `--min-samples=2` in the command.

Author: tbkka

benchmark/cmake/modules/AddSwiftBenchmarkSuite.cmake

@@ -751,6 +751,26 @@ function(swift_benchmark_compile)
         DEPENDS ${platform_executables})
 
     if(NOT SWIFT_BENCHMARK_BUILT_STANDALONE AND "${SWIFT_BENCHMARK_COMPILE_PLATFORM}" STREQUAL "macosx")
+      set(SWIFT_BENCHMARK_ARGS)
+      list(APPEND SWIFT_BENCHMARK_ARGS "--output-dir")
+      list(APPEND SWIFT_BENCHMARK_ARGS "${CMAKE_CURRENT_BINARY_DIR}/logs")
+      list(APPEND SWIFT_BENCHMARK_ARGS "--swift-repo")
+      list(APPEND SWIFT_BENCHMARK_ARGS "${SWIFT_SOURCE_DIR}")
+      list(APPEND SWIFT_BENCHMARK_ARGS "--architecture")
+      list(APPEND SWIFT_BENCHMARK_ARGS "${arch}")
+
+      set(SWIFT_O_BENCHMARK_ARGS)
+      if(DEFINED SWIFT_BENCHMARK_NUM_O_ITERATIONS)
+        list(APPEND SWIFT_O_BENCHMARK_ARGS "--independent-samples")
+        list(APPEND SWIFT_O_BENCHMARK_ARGS "${SWIFT_BENCHMARK_NUM_O_ITERATIONS}")
+      endif()
+
+      set(SWIFT_ONONE_BENCHMARK_ARGS)
+      if(DEFINED SWIFT_BENCHMARK_NUM_ONONE_ITERATIONS)
+        list(APPEND SWIFT_O_BENCHMARK_ARGS "--independent-samples")
+        list(APPEND SWIFT_O_BENCHMARK_ARGS "${SWIFT_BENCHMARK_NUM_ONONE_ITERATIONS}")
+      endif()
+
       add_custom_command(
           TARGET "${executable_target}"
           POST_BUILD
@@ -759,15 +779,13 @@ function(swift_benchmark_compile)
 
       add_custom_target("check-${executable_target}"
           COMMAND "${swift-bin-dir}/Benchmark_Driver" "run"
-                  "-o" "O" "--output-dir" "${CMAKE_CURRENT_BINARY_DIR}/logs"
-                  "--architecture" "${arch}"
-                  "--swift-repo" "${SWIFT_SOURCE_DIR}"
-                  "--independent-samples" "${SWIFT_BENCHMARK_NUM_O_ITERATIONS}"
+                  "-o" "O"
+		  ${SWIFT_BENCHMARK_ARGS}
+		  ${SWIFT_O_BENCHMARK_ARGS}
           COMMAND "${swift-bin-dir}/Benchmark_Driver" "run"
-                  "-o" "Onone" "--output-dir" "${CMAKE_CURRENT_BINARY_DIR}/logs"
-                  "--swift-repo" "${SWIFT_SOURCE_DIR}"
-                  "--architecture" "${arch}"
-                  "--independent-samples" "${SWIFT_BENCHMARK_NUM_ONONE_ITERATIONS}"
+                  "-o" "Onone"
+		  ${SWIFT_BENCHMARK_ARGS}
+		  ${SWIFT_ONONE_BENCHMARK_ARGS}
           COMMAND "${swift-bin-dir}/Benchmark_Driver" "compare"
                   "--log-dir" "${CMAKE_CURRENT_BINARY_DIR}/logs"
                   "--swift-repo" "${SWIFT_SOURCE_DIR}"

benchmark/scripts/Benchmark_Driver

@@ -226,6 +226,8 @@ class BenchmarkDriver(object):
             cmd.extend([str(self.test_number.get(name, name)) for name in self.tests])
         if num_samples > 0:
             cmd.append("--num-samples={0}".format(num_samples))
+        else:
+            cmd.append("--min-samples=2")
         if num_iters > 0:
             cmd.append("--num-iters={0}".format(num_iters))
         if sample_time > 0: