Line data    Source code

       1            0 : // Distributed under the MIT License.
       2              : // See LICENSE.txt for details.
       3              : 
       4              : #pragma once
       5              : 
       6              : #include <iosfwd>
       7              : 
       8              : namespace sys {
       9              : /// The cache location to prefetch data to.
      10            1 : enum class PrefetchTo : int {
      11              :   /// Prefetch into L1 data cache
      12              :   ///
      13              :   /// Typically the fastest CPU cache, about 32 KB in size.
      14              :   L1Cache = 3,
      15              :   /// Prefetch into L2 data cache
      16              :   ///
      17              :   /// Typically the second fastest CPU cache, about 128 or 256 KB in size.
      18              :   L2Cache = 2,
      19              :   /// Prefetch into L3 data cache
      20              :   ///
      21              :   /// Typically the slowest CPU cache and is shared among multiple cores with
      22              :   /// sizes varying by factors of several.
      23              :   L3Cache = 1,
      24              :   /// Non-temporal is an element that is unlikely to be re-used. E.g., read
      25              :   /// once, written but never read.
      26              :   NonTemporal = 0,
      27              :   /// Prefetch to L1 data cache for writing
      28              :   WriteL1Cache = 7,
      29              :   /// Prefetch to L2 data cache for writing
      30              :   WriteL2Cache = 6
      31              : };
      32              : 
      33              : /// \brief Prefetch data into a specific level of data cache.
      34              : template <PrefetchTo CacheLocation>
      35              : #if defined(__GNUC__)
      36              : __attribute__((always_inline)) inline
      37              : #endif
      38            1 : void prefetch(const void* address_to_prefetch) {
      39              :   // The enum values are bit flags where the lowest two bits (right-most)
      40              :   // control the cache level and the 3rd bit controls whether it is a write-only
      41              :   // or read-write operation.
      42              :   __builtin_prefetch(address_to_prefetch,
      43              :                      (static_cast<int>(CacheLocation) >> 2) & 1,
      44              :                      static_cast<int>(CacheLocation) & 0x3);
      45              : }
      46              : 
      47            0 : std::ostream& operator<<(std::ostream& os, PrefetchTo cache_location);
      48              : }  // namespace sys