Export of internal Abseil changes

--
0acc8470116819a62fd5ebbc2c64fdd703c93331 by Abseil Team <absl-team@google.com>:

Add an attribute to HashtablezInfo which performs a bitwise XOR on all hashes. The purposes of this attribute is to identify if identical hash tables are being created. If we see a large number of identical tables, it's likely the code can be improved by using a common table as opposed to keep rebuilding the same one.

PiperOrigin-RevId: 356338043
GitOrigin-RevId: 0acc8470116819a62fd5ebbc2c64fdd703c93331
Change-Id: If7d0a96629144fb41e6bef1ec93345a22df40733

1 files changed, 6 insertions, 0 deletions

diff --git a/absl/container/internal/hashtablez_sampler_test.cc b/absl/container/internal/hashtablez_sampler_test.cc
index 8d10a1e9..5f4c83b7 100644
--- a/absl/container/internal/hashtablez_sampler_test.cc
+++ b/absl/container/internal/hashtablez_sampler_test.cc
@@ -89,6 +89,7 @@ TEST(HashtablezInfoTest, PrepareForSampling) {
   EXPECT_EQ(info.total_probe_length.load(), 0);
   EXPECT_EQ(info.hashes_bitwise_or.load(), 0);
   EXPECT_EQ(info.hashes_bitwise_and.load(), ~size_t{});
+  EXPECT_EQ(info.hashes_bitwise_xor.load(), 0);
   EXPECT_GE(info.create_time, test_start);
 
   info.capacity.store(1, std::memory_order_relaxed);
@@ -98,6 +99,7 @@ TEST(HashtablezInfoTest, PrepareForSampling) {
   info.total_probe_length.store(1, std::memory_order_relaxed);
   info.hashes_bitwise_or.store(1, std::memory_order_relaxed);
   info.hashes_bitwise_and.store(1, std::memory_order_relaxed);
+  info.hashes_bitwise_xor.store(1, std::memory_order_relaxed);
   info.create_time = test_start - absl::Hours(20);
 
   info.PrepareForSampling();
@@ -109,6 +111,7 @@ TEST(HashtablezInfoTest, PrepareForSampling) {
   EXPECT_EQ(info.total_probe_length.load(), 0);
   EXPECT_EQ(info.hashes_bitwise_or.load(), 0);
   EXPECT_EQ(info.hashes_bitwise_and.load(), ~size_t{});
+  EXPECT_EQ(info.hashes_bitwise_xor.load(), 0);
   EXPECT_GE(info.create_time, test_start);
 }
 
@@ -133,14 +136,17 @@ TEST(HashtablezInfoTest, RecordInsert) {
   EXPECT_EQ(info.max_probe_length.load(), 6);
   EXPECT_EQ(info.hashes_bitwise_and.load(), 0x0000FF00);
   EXPECT_EQ(info.hashes_bitwise_or.load(), 0x0000FF00);
+  EXPECT_EQ(info.hashes_bitwise_xor.load(), 0x0000FF00);
   RecordInsertSlow(&info, 0x000FF000, 4 * kProbeLength);
   EXPECT_EQ(info.max_probe_length.load(), 6);
   EXPECT_EQ(info.hashes_bitwise_and.load(), 0x0000F000);
   EXPECT_EQ(info.hashes_bitwise_or.load(), 0x000FFF00);
+  EXPECT_EQ(info.hashes_bitwise_xor.load(), 0x000F0F00);
   RecordInsertSlow(&info, 0x00FF0000, 12 * kProbeLength);
   EXPECT_EQ(info.max_probe_length.load(), 12);
   EXPECT_EQ(info.hashes_bitwise_and.load(), 0x00000000);
   EXPECT_EQ(info.hashes_bitwise_or.load(), 0x00FFFF00);
+  EXPECT_EQ(info.hashes_bitwise_xor.load(), 0x00F00F00);
 }
 
 TEST(HashtablezInfoTest, RecordErase) {