Align statistics

Use Yield macro to make it a little more portable between platforms.

port/port_posix.h

@@ -16,6 +16,8 @@
 // in fact, we could use that one
 #define ROCKSDB_PRIszt "zu"
 
+#define __declspec(S)
+
 #define ROCKSDB_NOEXCEPT noexcept
 
 #undef PLATFORM_IS_LITTLE_ENDIAN

port/win/port_win.h

@@ -245,7 +245,7 @@ extern void InitOnce(OnceType* once, void (*initializer)());
 
 static inline void AsmVolatilePause() {
 #if defined(_M_IX86) || defined(_M_X64)
-  ::_mm_pause();
+  YieldProcessor();
 #endif
   // it would be nice to get "wfe" on ARM here
 }

util/statistics.h

@@ -61,7 +61,13 @@ class StatisticsImpl : public Statistics {
     char padding[64 - sizeof(std::atomic_uint_fast64_t)];
   };
 
-  Ticker tickers_[INTERNAL_TICKER_ENUM_MAX] __attribute__((aligned(64)));
+  static_assert(sizeof(Ticker) == 64, "Expecting to fit into 64 bytes");
+
+  // Attributes expand to nothing depending on the platform
+  __declspec(align(64))
+  Ticker tickers_[INTERNAL_TICKER_ENUM_MAX]
+     __attribute__((aligned(64)));
+  __declspec(align(64))
   HistogramImpl histograms_[INTERNAL_HISTOGRAM_ENUM_MAX]
       __attribute__((aligned(64)));
 };