Merge abi diffs, improve linking performance.

Bug: 38325544

Test:
As shown by out/build.trace.gz when using built header-abi-linker to
link .sdump files produced by header-abi-linker.

Without fix:
Time taken to produce libc.so.lsdump by header-abi-linker => ~51 sec
With fix:
Time taken to produce libc.so.lsdump by header-abi-linker => ~3 sec

Bug: 38325929

Test: merged abiff reports of libjpeg, libc.

Change-Id: Iae54f4754d8b0407fabdb8bc8550a7f7b3479f8f

vndk/tools/header-checker/merge-abi-diff/src/merge_abi_diff.cpp

@@ -0,0 +1,156 @@
+// Copyright (C) 2016 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.
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-parameter"
+#pragma clang diagnostic ignored "-Wnested-anon-types"
+#include "proto/abi_dump.pb.h"
+#include "proto/abi_diff.pb.h"
+#pragma clang diagnostic pop
+
+#include <header_abi_util.h>
+
+#include <llvm/Support/CommandLine.h>
+#include <llvm/Support/raw_ostream.h>
+
+#include <google/protobuf/text_format.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+
+#include <memory>
+#include <fstream>
+#include <iostream>
+#include <string>
+#include <vector>
+
+#include <stdlib.h>
+
+static llvm::cl::OptionCategory merge_abi_diff_category(
+    "merge-abi-diff options");
+
+static llvm::cl::list<std::string> diff_report_list(
+    llvm::cl::Positional, llvm::cl::desc("<diff-reports>"), llvm::cl::Required,
+    llvm::cl::cat(merge_abi_diff_category), llvm::cl::OneOrMore);
+
+static llvm::cl::opt<std::string> merged_diff_report(
+    "o", llvm::cl::desc("<merged-diff-report>"), llvm::cl::Required,
+    llvm::cl::cat(merge_abi_diff_category));
+
+static llvm::cl::opt<bool> advice_only(
+    "advice-only", llvm::cl::desc("Advisory mode only"), llvm::cl::Optional,
+    llvm::cl::cat(merge_abi_diff_category));
+
+static llvm::cl::opt<bool> do_not_break_on_extensions(
+    "allow-extensions",
+    llvm::cl::desc("Do not return a non zero status on extensions"),
+    llvm::cl::Optional, llvm::cl::cat(merge_abi_diff_category));
+
+typedef abi_diff::CompatibilityStatus CompatibilityStatus;
+
+static bool IsStatusDowngraded(const CompatibilityStatus &old_status,
+                               const CompatibilityStatus &new_status) {
+  bool status_downgraded = false;
+  switch (old_status) {
+    case CompatibilityStatus::EXTENSION:
+      if (new_status == CompatibilityStatus::INCOMPATIBLE) {
+        status_downgraded = true;
+      }
+      break;
+    case CompatibilityStatus::COMPATIBLE:
+      if (new_status != CompatibilityStatus::COMPATIBLE) {
+        status_downgraded = true;
+      }
+      break;
+    default:
+      break;
+  }
+  return status_downgraded;
+}
+
+static CompatibilityStatus MergeDiffReports(
+    const std::vector<std::string> &diff_reports,
+    const std::string &merged_diff_report) {
+
+  abi_diff::MergedTranslationUnitDiff merged_tu_diff;
+  std::ofstream text_output(merged_diff_report);
+  google::protobuf::io::OstreamOutputStream text_os(&text_output);
+  CompatibilityStatus status = CompatibilityStatus::COMPATIBLE;
+
+  for (auto &&i : diff_reports) {
+    abi_diff::TranslationUnitDiff diff_tu;
+    std::ifstream input(i);
+    google::protobuf::io::IstreamInputStream text_is(&input);
+    if (!google::protobuf::TextFormat::Parse(&text_is, &diff_tu)) {
+      llvm::errs() << "Failed to parse diff report\n";
+      ::exit(1);
+    }
+    abi_diff::ConciseDiffReportInformation *added_tu_diff =
+        merged_tu_diff.add_diff_reports();
+    if (!added_tu_diff) {
+      llvm::errs() << "Failed to add diff report to merged report\n";
+      ::exit(1);
+    }
+    CompatibilityStatus new_status = diff_tu.compatibility_status();
+    added_tu_diff->set_lib_name(diff_tu.lib_name());
+    added_tu_diff->set_arch(diff_tu.arch());
+    added_tu_diff->set_diff_report_path(i);
+    added_tu_diff->set_compatibility_status(new_status);
+    // Only, if the status is downgraded, change it.
+    if (IsStatusDowngraded(status, new_status)) {
+      status = new_status;
+    }
+  }
+
+  if (!google::protobuf::TextFormat::Print(merged_tu_diff, &text_os)) {
+    llvm::errs() << "Serialization to ostream failed\n";
+    ::exit(1);
+  }
+  return status;
+}
+
+int main(int argc, const char **argv) {
+  GOOGLE_PROTOBUF_VERIFY_VERSION;
+  llvm::cl::ParseCommandLineOptions(argc, argv, "merge-abi-diff");
+  CompatibilityStatus extension_or_incompatible =
+      MergeDiffReports(diff_report_list, merged_diff_report);
+  std::string status_str = "";
+  switch (extension_or_incompatible) {
+    case CompatibilityStatus::INCOMPATIBLE:
+      status_str = "broken";
+      break;
+    case CompatibilityStatus::EXTENSION:
+      status_str = "extended";
+      break;
+    default:
+      break;
+  }
+  if (extension_or_incompatible) {
+    llvm::errs() << "******************************************************\n"
+                 << "VNDK Abi "
+                 << status_str
+                 << ":"
+                 << " Please check compatiblity report at : "
+                 << merged_diff_report << "\n"
+                 << "*****************************************************\n";
+  }
+
+  if (do_not_break_on_extensions &&
+      extension_or_incompatible == CompatibilityStatus::EXTENSION) {
+      extension_or_incompatible = CompatibilityStatus::COMPATIBLE;
+  }
+
+  if (!advice_only) {
+    return extension_or_incompatible;
+  }
+  return CompatibilityStatus::COMPATIBLE;
+}