[NFC][sanitizer] Add basic hash test

[eugenis]

I'm not sure what does this test test.
Do we depend anywhere on the hash function producing these exact values, or is it part of an abi contract?

[vitalybuka]

In D111176#3043670, @eugenis wrote:

I'm not sure what does this test test.
Do we depend anywhere on the hash function producing these exact values, or is it part of an abi contract?

It tests MurMur2HashBuilder implementation, it should return precise values.

[vitalybuka]

In D111176#3043670, @eugenis wrote:

I'm not sure what does this test test.
Do we depend anywhere on the hash function producing these exact values, or is it part of an abi contract?

Almost all out unittest are not about contract or ABI, for that we usually use lit tests.
This is regression tests, if it fail, we have a problem.

[vitalybuka]

repaced constants tested on reference implementation

[morehouse]

compiler-rt/lib/sanitizer_common/tests/sanitizer_hash_test.cpp

10

Maybe explain here that these are regression tests to ensure consistent hash results and that we don't unintentionally change the hash algorithm.

[eugenis]

LGTM

compiler-rt/lib/sanitizer_common/tests/CMakeLists.txt

set(SANITIZER_UNITTESTS
   sanitizer_atomic_test.cpp
   sanitizer_bitvector_test.cpp
   sanitizer_bvgraph_test.cpp
   sanitizer_chained_origin_depot_test.cpp
   sanitizer_common_test.cpp
   sanitizer_deadlock_detector_test.cpp
   sanitizer_flags_test.cpp
   sanitizer_format_interceptor_test.cpp
+  sanitizer_hash_test.cpp
   sanitizer_ioctl_test.cpp
   sanitizer_libc_test.cpp
   sanitizer_linux_test.cpp
   sanitizer_list_test.cpp
   sanitizer_mac_test.cpp
   sanitizer_mutex_test.cpp
   sanitizer_nolibc_test.cpp
   sanitizer_posix_test.cpp

compiler-rt/lib/sanitizer_common/tests/sanitizer_hash_test.cpp

+//===-- sanitizer_hash_test.cpp -------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of Sanitizers.
+//
+//===----------------------------------------------------------------------===//
+#include "sanitizer_common/sanitizer_hash.h"
+
+#include "gtest/gtest.h"
+
+namespace __sanitizer {
+
+// Tests matche a few hashes generated by https://github.com/aappleby/smhasher.
+
+TEST(SanitizerCommon, Hash32Seed) {
+  EXPECT_EQ(MurMur2HashBuilder(0).get(), 275646681u);
+  EXPECT_EQ(MurMur2HashBuilder(1).get(), 3030210376u);
+  EXPECT_EQ(MurMur2HashBuilder(3).get(), 1816185114u);
+}
+
+TEST(SanitizerCommon, Hash32Add) {
+  MurMur2HashBuilder h(123 * sizeof(u32));
+  for (u32 i = 0; i < 123; ++i) h.add(i);
+  EXPECT_EQ(h.get(), 351963665u);
+  for (u32 i = 0; i < 123; ++i) h.add(-i);
+  EXPECT_EQ(h.get(), 2640061027u);
+}
+
+}  // namespace __sanitizer