Optimize Google Test process startup

Google Test performs hidden test registration during process
startup. For test binaries that contain a large number of tests, this
registration can be costly. In this CL, we reduce the overhead of
registration via several tactics:

- Treat CodeLocation and FilePath as value types, using std::move to
  pass them around.
- Reduce string copies in various places by either passing std::string
  values via std::move, or passing const-refs to std::string instances.
- Use std::to_string to stringify an int in DefaultParamName rather than
  a std::stringstream.
- Pull some std::string instances out of nested loops in
  ParameterizedTestSuiteInfo::RegisterTests so as to reuse some
  allocations, and replace stringstream with ordinary string appends.
- Use std::unordered_map in UnitTestImpl::GetTestSuite and
  ParameterizedTestSuiteRegistry::GetTestSuitePatternHolder to spend a
  little memory to turn O(N) lookups into constant time lookpus.
- Use range-based for loops in various places.
- Use emplace-ish methods to add to containers where appropriate.

All together, these changes reduce the overall runtime of a series of 50
death tests in a single Chromium test executable by ~38% due to the
fact that the registration costs are paid in every death test's child
process.

PiperOrigin-RevId: 612763676
Change-Id: I1f46e012ccb9004c009e1027e4f7c38780ffb9e2

1 files changed, 16 insertions, 4 deletions

diff --git a/googletest/src/gtest-internal-inl.h b/googletest/src/gtest-internal-inl.h
index 6dea34f..6a7f4dd 100644
--- a/googletest/src/gtest-internal-inl.h
+++ b/googletest/src/gtest-internal-inl.h
@@ -46,6 +46,7 @@
 #include <memory>
 #include <set>
 #include <string>
+#include <unordered_map>
 #include <vector>
 
 #include "gtest/internal/gtest-port.h"
@@ -649,13 +650,15 @@ class GTEST_API_ UnitTestImpl {
   //                    this is not a typed or a type-parameterized test.
   //   set_up_tc:       pointer to the function that sets up the test suite
   //   tear_down_tc:    pointer to the function that tears down the test suite
-  TestSuite* GetTestSuite(const char* test_suite_name, const char* type_param,
+  TestSuite* GetTestSuite(const std::string& test_suite_name,
+                          const char* type_param,
                           internal::SetUpTestSuiteFunc set_up_tc,
                           internal::TearDownTestSuiteFunc tear_down_tc);
 
 //  Legacy API is deprecated but still available
 #ifndef GTEST_REMOVE_LEGACY_TEST_CASEAPI_
-  TestCase* GetTestCase(const char* test_case_name, const char* type_param,
+  TestCase* GetTestCase(const std::string& test_case_name,
+                        const char* type_param,
                         internal::SetUpTestSuiteFunc set_up_tc,
                         internal::TearDownTestSuiteFunc tear_down_tc) {
     return GetTestSuite(test_case_name, type_param, set_up_tc, tear_down_tc);
@@ -681,13 +684,13 @@ class GTEST_API_ UnitTestImpl {
     // AddTestInfo(), which is called to register a TEST or TEST_F
     // before main() is reached.
     if (original_working_dir_.IsEmpty()) {
-      original_working_dir_.Set(FilePath::GetCurrentDir());
+      original_working_dir_ = FilePath::GetCurrentDir();
       GTEST_CHECK_(!original_working_dir_.IsEmpty())
           << "Failed to get the current working directory.";
     }
 #endif  // GTEST_HAS_FILE_SYSTEM
 
-    GetTestSuite(test_info->test_suite_name(), test_info->type_param(),
+    GetTestSuite(test_info->test_suite_name_, test_info->type_param(),
                  set_up_tc, tear_down_tc)
         ->AddTestInfo(test_info);
   }
@@ -823,6 +826,12 @@ class GTEST_API_ UnitTestImpl {
   bool catch_exceptions() const { return catch_exceptions_; }
 
  private:
+  struct CompareTestSuitesByPointer {
+    bool operator()(const TestSuite* lhs, const TestSuite* rhs) const {
+      return lhs->name_ < rhs->name_;
+    };
+  };
+
   friend class ::testing::UnitTest;
 
   // Used by UnitTest::Run() to capture the state of
@@ -873,6 +882,9 @@ class GTEST_API_ UnitTestImpl {
   // elements in the vector.
   std::vector<TestSuite*> test_suites_;
 
+  // The set of TestSuites by name.
+  std::unordered_map<std::string, TestSuite*> test_suites_by_name_;
+
   // Provides a level of indirection for the test suite list to allow
   // easy shuffling and restoring the test suite order.  The i-th
   // element of this vector is the index of the i-th test suite in the