kernel_function.h

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/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
 *
 * SPDX-License-Identifier: Apache-2.0 */
 
#pragma once
 
#include "util/debug.h"
#include "util/system.h"
 
CCL_NAMESPACE_BEGIN
 
/* A wrapper around per-microarchitecture variant of a kernel function.
 *
 * Provides a function-call-like API which gets routed to the most suitable implementation.
 *
 * For example, on a computer which only has SSE4.2 the kernel_sse42 will be used. */
template<typename FunctionType> class CPUKernelFunction {
 public:
  CPUKernelFunction(FunctionType kernel_default,
                    FunctionType kernel_sse42,
                    FunctionType kernel_avx2)
  {
    kernel_info_ = get_best_kernel_info(kernel_default, kernel_sse42, kernel_avx2);
  }
 
  template<typename... Args> inline auto operator()(Args... args) const
  {
    assert(kernel_info_.kernel);
 
    return kernel_info_.kernel(args...);
  }
 
  const char *get_uarch_name() const
  {
    return kernel_info_.uarch_name;
  }
 
 protected:
  /* Helper class which allows to pass human-readable microarchitecture name together with function
   * pointer. */
  class KernelInfo {
   public:
    KernelInfo() : KernelInfo("", nullptr) {}
 
    /* TODO(sergey): Use string view, to have higher-level functionality (i.e. comparison) without
     * memory allocation. */
    KernelInfo(const char *uarch_name, FunctionType kernel)
        : uarch_name(uarch_name), kernel(kernel)
    {
    }
 
    const char *uarch_name;
    FunctionType kernel;
  };
 
  KernelInfo get_best_kernel_info(FunctionType kernel_default,
                                  FunctionType kernel_sse42,
                                  FunctionType kernel_avx2)
  {
    /* Silence warnings about unused variables when compiling without some architectures. */
    (void)kernel_sse42;
    (void)kernel_avx2;
 
#ifdef WITH_CYCLES_OPTIMIZED_KERNEL_AVX2
    if (DebugFlags().cpu.has_avx2() && system_cpu_support_avx2()) {
      return KernelInfo("AVX2", kernel_avx2);
    }
#endif
 
#ifdef WITH_CYCLES_OPTIMIZED_KERNEL_SSE42
    if (DebugFlags().cpu.has_sse42() && system_cpu_support_sse42()) {
      return KernelInfo("SSE4.2", kernel_sse42);
    }
#endif
 
    return KernelInfo("default", kernel_default);
  }
 
  KernelInfo kernel_info_;
};
 
CCL_NAMESPACE_END