[NFC][sanitizer] Add StackStoreTest

[morehouse]

LGTM

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

set(SANITIZER_UNITTESTS
   sanitizer_mac_test.cpp
   sanitizer_mutex_test.cpp
   sanitizer_nolibc_test.cpp
   sanitizer_posix_test.cpp
   sanitizer_printf_test.cpp
   sanitizer_procmaps_test.cpp
   sanitizer_ring_buffer_test.cpp
   sanitizer_quarantine_test.cpp
+  sanitizer_stack_store_test.cpp
   sanitizer_stackdepot_test.cpp
   sanitizer_stacktrace_printer_test.cpp
   sanitizer_stacktrace_test.cpp
   sanitizer_stoptheworld_test.cpp
   sanitizer_suppressions_test.cpp
   sanitizer_symbolizer_test.cpp
   sanitizer_test_main.cpp
   sanitizer_thread_registry_test.cpp

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

+//===-- sanitizer_stack_store_test.cpp --------------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+#include "sanitizer_common/sanitizer_stack_store.h"
+
+#include <algorithm>
+#include <numeric>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "sanitizer_hash.h"
+#include "sanitizer_stacktrace.h"
+
+namespace __sanitizer {
+
+class StackStoreTest : public testing::Test {
+ protected:
+  void SetUp() override {}
+  void TearDown() override { store_.TestOnlyUnmap(); }
+
+  template <typename Fn>
+  void ForEachTrace(Fn fn, uptr n = 1000000) {
+    std::vector<uptr> frames(kStackTraceMax);
+    std::iota(frames.begin(), frames.end(), 1);
+    MurMur2HashBuilder h(0);
+    for (uptr i = 0; i < n; ++i) {
+      h.add(i);
+      u32 size = h.get() % kStackTraceMax;
+      h.add(i);
+      uptr tag = h.get() % 256;
+      StackTrace s(frames.data(), size, tag);
+      fn(s);
+      std::next_permutation(frames.begin(), frames.end());
+    };
+  }
+
+  StackStore store_ = {};
+};
+
+TEST_F(StackStoreTest, Basic) {
+  std::vector<StackStore::Id> ids;
+  ForEachTrace([&](const StackTrace& s) { ids.push_back(store_.Store(s)); });
+
+  auto id = ids.begin();
+  ForEachTrace([&](const StackTrace& s) {
+    StackTrace trace = store_.Load(*(id++));
+    EXPECT_EQ(s.size, trace.size);
+    EXPECT_EQ(s.tag, trace.tag);
+    EXPECT_EQ(std::vector<uptr>(s.trace, s.trace + s.size),
+              std::vector<uptr>(trace.trace, trace.trace + trace.size));
+  });
+}
+
+TEST_F(StackStoreTest, Allocated) {
+  EXPECT_LE(store_.Allocated(), 0x100000u);
+  std::vector<StackStore::Id> ids;
+  ForEachTrace([&](const StackTrace& s) { ids.push_back(store_.Store(s)); });
+  EXPECT_NEAR(store_.Allocated(), FIRST_32_SECOND_64(500000000u, 1000000000u),
+              FIRST_32_SECOND_64(50000000u, 100000000u));
+  store_.TestOnlyUnmap();
+  EXPECT_LE(store_.Allocated(), 0x100000u);
+}
+
+}  // namespace __sanitizer