prefer thread_local over FOLLY_TLS in F14

Reviewed By: Orvid

Differential Revision: D27582035

fbshipit-source-id: 0f0c35adca1c44dcd0ef88f2443f769d7991e6aa

folly/container/detail/F14Table.cpp

@@ -36,30 +36,29 @@ EmptyTagVectorType kEmptyTagVector = {};
 
 //// Debug and ASAN stuff
 
-#if defined(FOLLY_TLS) && (!defined(NDEBUG) || FOLLY_LIBRARY_SANITIZE_ADDRESS)
-#define FOLLY_F14_DETAIL_TLS_SIZE_T thread_local std::size_t
-#else
-#define FOLLY_F14_DETAIL_TLS_SIZE_T std::atomic<std::size_t>
-#endif
-
 bool tlsPendingSafeInserts(std::ptrdiff_t delta) {
-  static FOLLY_F14_DETAIL_TLS_SIZE_T value{0};
+  static std::atomic<size_t> value_non_tl{0};
+  static thread_local std::atomic<size_t> value_tl{0};
+  auto& value = kIsDebug || kIsLibrarySanitizeAddress ? value_tl : value_non_tl;
 
   FOLLY_SAFE_DCHECK(delta >= -1, "");
-  std::size_t v = value;
+  std::size_t v = value.load(std::memory_order_relaxed);
   if (delta > 0 || (delta == -1 && v > 0)) {
     v += delta;
     v = std::min(std::numeric_limits<std::size_t>::max() / 2, v);
-    value = v;
+    value.store(v, std::memory_order_relaxed);
   }
   return v != 0;
 }
 
 std::size_t tlsMinstdRand(std::size_t n) {
+  static std::atomic<uint32_t> state_non_tl{0};
+  static thread_local std::atomic<uint32_t> state_tl{0};
+  auto& state = kIsDebug || kIsLibrarySanitizeAddress ? state_tl : state_non_tl;
+
   FOLLY_SAFE_DCHECK(n > 0, "");
 
-  static FOLLY_F14_DETAIL_TLS_SIZE_T state{0};
-  auto s = static_cast<uint32_t>(state);
+  auto s = state.load(std::memory_order_relaxed);
   if (s == 0) {
     uint64_t seed = static_cast<uint64_t>(
         std::chrono::steady_clock::now().time_since_epoch().count());
@@ -67,7 +66,7 @@ std::size_t tlsMinstdRand(std::size_t n) {
   }
 
   s = static_cast<uint32_t>((s * uint64_t{48271}) % uint64_t{2147483647});
-  state = s;
+  state.store(s, std::memory_order_relaxed);
   return std::size_t{s} % n;
 }