Perform profile file analysis in dex2oat

Dex2oat can accept now multiple profile files to drive a profile based
compilation. --profile-file and --reference-profile-file speficy a pair
of profile files which will be evaluated for significant differences
before starting the compilation. If the difference is insignificant
(according to some internal metric) the compilation is skipped and a
message is logged.

Multiple pairs of --profile-file and --reference-profile-file can be
specified. This effectively enables multi user support since profiles
for different users will be kept separately.

--reference-profile-file can be left out, case in which the decision is
solely based on --profile-file. If both flags are present, then their
repetition should form unique pairs.

If the compilation is performed and --reference-profile-file is given
then its data is merged with the data from the corresponding --profile-
file and saved back to the file.

If no profile flags are given, dex2oat proceeds as before and compiles
the dex files unconditionally.

As part of this change
- merge ProfileCompilationInfo and OfflineProfilingInfo under the same
object. There was no use to keep them separate anymore.
- SaveProfilingInfo now merges the data with what was in
the file before instead of overwriting it.

Bug: 26080105

Change-Id: Ia8c8b55587d468bca5179f78941854285426234d

1 files changed, 69 insertions, 0 deletions

diff --git a/compiler/profile_assistant.cc b/compiler/profile_assistant.cc
new file mode 100644
index 0000000000..81f2a5692d
--- /dev/null
+++ b/compiler/profile_assistant.cc
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "profile_assistant.h"
+
+namespace art {
+
+// Minimum number of new methods that profiles must contain to enable recompilation.
+static constexpr const uint32_t kMinNewMethodsForCompilation = 10;
+
+bool ProfileAssistant::ProcessProfiles(
+      const std::vector<std::string>& profile_files,
+      const std::vector<std::string>& reference_profile_files,
+      /*out*/ ProfileCompilationInfo** profile_compilation_info) {
+  DCHECK(!profile_files.empty());
+  DCHECK(reference_profile_files.empty() ||
+      (profile_files.size() == reference_profile_files.size()));
+
+  std::vector<ProfileCompilationInfo> new_info(profile_files.size());
+  bool should_compile = false;
+  // Read the main profile files.
+  for (size_t i = 0; i < profile_files.size(); i++) {
+    if (!new_info[i].Load(profile_files[i])) {
+      LOG(WARNING) << "Could not load profile file: " << profile_files[i];
+      return false;
+    }
+    // Do we have enough new profiled methods that will make the compilation worthwhile?
+    should_compile |= (new_info[i].GetNumberOfMethods() > kMinNewMethodsForCompilation);
+  }
+  if (!should_compile) {
+    *profile_compilation_info = nullptr;
+    return true;
+  }
+
+  std::unique_ptr<ProfileCompilationInfo> result(new ProfileCompilationInfo());
+  for (size_t i = 0; i < new_info.size(); i++) {
+    // Merge all data into a single object.
+    result->Load(new_info[i]);
+    // If we have any reference profile information merge their information with
+    // the current profiles and save them back to disk.
+    if (!reference_profile_files.empty()) {
+      if (!new_info[i].Load(reference_profile_files[i])) {
+        LOG(WARNING) << "Could not load reference profile file: " << reference_profile_files[i];
+        return false;
+      }
+      if (!new_info[i].Save(reference_profile_files[i])) {
+        LOG(WARNING) << "Could not save reference profile file: " << reference_profile_files[i];
+        return false;
+      }
+    }
+  }
+  *profile_compilation_info = result.release();
+  return true;
+}
+
+}  // namespace art