chromium/third_party/dawn/src/dawn/native/CacheRequest.h

// Copyright 2022 The Dawn & Tint Authors
//
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#ifndef SRC_DAWN_NATIVE_CACHEREQUEST_H_
#define SRC_DAWN_NATIVE_CACHEREQUEST_H_

#include <memory>
#include <string>
#include <utility>

#include "dawn/common/Assert.h"
#include "dawn/common/Compiler.h"
#include "dawn/native/Blob.h"
#include "dawn/native/BlobCache.h"
#include "dawn/native/CacheKey.h"
#include "dawn/native/CacheResult.h"
#include "dawn/native/Device.h"
#include "dawn/native/Error.h"
#include "dawn/native/VisitableMembers.h"
#include "dawn/platform/metrics/HistogramMacros.h"

namespace dawn::native {

namespace detail {

void LogCacheHitError(std::unique_ptr<ErrorData> error);

}  // namespace detail

// Implementation of a CacheRequest which provides a LoadOrRun friend function which can be found
// via argument-dependent lookup. So, it doesn't need to be called with a fully qualified function
// name.
//
// Example usage:
//   Request r = { ... };
//   ResultOrError<CacheResult<T>> cacheResult =
//       LoadOrRun(device, std::move(r),
//                 [](Blob blob) -> T { /* handle cache hit */ },
//                 [](Request r) -> ResultOrError<T> { /* handle cache miss */ }
//       );
// Or with free functions:
///  T OnCacheHit(Blob blob) { ... }
//   ResultOrError<T> OnCacheMiss(Request r) { ... }
//   // ...
//   Request r = { ... };
//   auto result = LoadOrRun(device, std::move(r), OnCacheHit, OnCacheMiss);
//
// LoadOrRun generates a CacheKey from the request and loads from the device's BlobCache. On cache
// hit, calls CacheHitFn and returns a CacheResult<T>. On cache miss or if CacheHitFn returned an
// Error, calls CacheMissFn -> ResultOrError<T> with the request data and returns a
// ResultOrError<CacheResult<T>>. CacheHitFn must return the same unwrapped type as CacheMissFn.
// i.e. it doesn't need to be wrapped in ResultOrError.
//
// CacheMissFn may not have any additional data bound to it. It may not be a lambda or std::function
// which captures additional information, so it can only operate on the request data. This is
// enforced with a compile-time static_assert, and ensures that the result created from the
// computation is exactly the data included in the CacheKey.
template <typename Request>
class CacheRequestImpl { … };

}  // namespace dawn::native

// Helper for X macro to declare a struct member.
#define DAWN_INTERNAL_CACHE_REQUEST_DECL_STRUCT_MEMBER(type, name) …

// Helper for X macro for recording cache request fields into a CacheKey.
#define DAWN_INTERNAL_CACHE_REQUEST_RECORD_KEY(type, name) …

// Helper X macro to define a CacheRequest struct.
// Example usage:
//   #define REQUEST_MEMBERS(X) \
//       X(int, a)              \
//       X(float, b)            \
//       X(Foo, foo)            \
//       X(Bar, bar)
//   DAWN_MAKE_CACHE_REQUEST(MyCacheRequest, REQUEST_MEMBERS)
//   #undef REQUEST_MEMBERS
#define DAWN_MAKE_CACHE_REQUEST(Request, MEMBERS) …

// Helper macro for the common pattern of DAWN_TRY_ASSIGN around LoadOrRun.
// Requires an #include of dawn/native/Error.h
#define DAWN_TRY_LOAD_OR_RUN(var, ...) …

#endif  // SRC_DAWN_NATIVE_CACHEREQUEST_H_