caffe2/perfkernels/common.h

// !!!! PLEASE READ !!!!
// Minimize (transitively) included headers from _avx*.cc because some of the
// functions defined in the headers compiled with platform dependent compiler
// options can be reused by other translation units generating illegal
// instruction run-time error.

// Common utilities for writing performance kernels and easy dispatching of
// different backends.
/*
The general workflow shall be as follows, say we want to
implement a functionality called void foo(int a, float b).

In foo.h, do:
   void foo(int a, float b);

In foo_avx512.cc, do:
   void foo__avx512(int a, float b) {
     [actual avx512 implementation]
   }

In foo_avx2.cc, do:
   void foo__avx2(int a, float b) {
     [actual avx2 implementation]
   }

In foo_avx.cc, do:
   void foo__avx(int a, float b) {
     [actual avx implementation]
   }

In foo.cc, do:
   // The base implementation should *always* be provided.
   void foo__base(int a, float b) {
     [base, possibly slow implementation]
   }
   decltype(foo__base) foo__avx512;
   decltype(foo__base) foo__avx2;
   decltype(foo__base) foo__avx;
   void foo(int a, float b) {
     // You should always order things by their preference, faster
     // implementations earlier in the function.
     AVX512_DO(foo, a, b);
     AVX2_DO(foo, a, b);
     AVX_DO(foo, a, b);
     BASE_DO(foo, a, b);
   }

*/
// Details: this functionality basically covers the cases for both build time
// and run time architecture support.
//
// During build time:
//    The build system should provide flags CAFFE2_PERF_WITH_AVX512,
//    CAFFE2_PERF_WITH_AVX2, and CAFFE2_PERF_WITH_AVX that corresponds to the
//    __AVX512F__, __AVX512DQ__, __AVX512VL__, __AVX2__, and __AVX__ flags the
//    compiler provides. Note that we do not use the compiler flags but rely on
//    the build system flags, because the common files (like foo.cc above) will
//    always be built without __AVX512F__, __AVX512DQ__, __AVX512VL__, __AVX2__
//    and __AVX__.
// During run time:
//    we use cpuinfo to identify cpu support and run the proper functions.

#pragma once

#if defined(CAFFE2_PERF_WITH_AVX512) || defined(CAFFE2_PERF_WITH_AVX2) \
     || defined(CAFFE2_PERF_WITH_AVX)
#include <cpuinfo.h>
#endif

// DO macros: these should be used in your entry function, similar to foo()
// above, that routes implementations based on CPU capability.

#define BASE_DO(funcname, ...) return funcname##__base(__VA_ARGS__);

#ifdef CAFFE2_PERF_WITH_AVX512
#define AVX512_DO(funcname, ...)                                   \
  {                                                                \
    static const bool isDo = cpuinfo_initialize() &&               \
        cpuinfo_has_x86_avx512f() && cpuinfo_has_x86_avx512dq() && \
        cpuinfo_has_x86_avx512vl();                                \
    if (isDo) {                                                    \
      return funcname##__avx512(__VA_ARGS__);                      \
    }                                                              \
  }
#else // CAFFE2_PERF_WITH_AVX512
#define AVX512_DO(funcname, ...)
#endif // CAFFE2_PERF_WITH_AVX512

#ifdef CAFFE2_PERF_WITH_AVX2
#define AVX2_DO(funcname, ...)                                               \
  {                                                                          \
    static const bool isDo = cpuinfo_initialize() && cpuinfo_has_x86_avx2(); \
    if (isDo) {                                                              \
      return funcname##__avx2(__VA_ARGS__);                                  \
    }                                                                        \
  }
#define AVX2_FMA_DO(funcname, ...)                                             \
  {                                                                            \
    static const bool isDo = cpuinfo_initialize() && cpuinfo_has_x86_avx2() && \
        cpuinfo_has_x86_fma3();                                                \
    if (isDo) {                                                                \
      return funcname##__avx2_fma(__VA_ARGS__);                                \
    }                                                                          \
  }
#else // CAFFE2_PERF_WITH_AVX2
#define AVX2_DO(funcname, ...)
#define AVX2_FMA_DO(funcname, ...)
#endif // CAFFE2_PERF_WITH_AVX2

#ifdef CAFFE2_PERF_WITH_AVX
#define AVX_DO(funcname, ...)                                               \
  {                                                                         \
    static const bool isDo = cpuinfo_initialize() && cpuinfo_has_x86_avx(); \
    if (isDo) {                                                             \
      return funcname##__avx(__VA_ARGS__);                                  \
    }                                                                       \
  }
#define AVX_F16C_DO(funcname, ...)                                            \
  {                                                                           \
    static const bool isDo = cpuinfo_initialize() && cpuinfo_has_x86_avx() && \
        cpuinfo_has_x86_f16c();                                               \
    if (isDo) {                                                               \
      return funcname##__avx_f16c(__VA_ARGS__);                               \
    }                                                                         \
  }
#else // CAFFE2_PERF_WITH_AVX
#define AVX_DO(funcname, ...)
#define AVX_F16C_DO(funcname, ...)
#endif // CAFFE2_PERF_WITH_AVX