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// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#ifndef LIB_JXL_BASE_CACHE_ALIGNED_H_
#define LIB_JXL_BASE_CACHE_ALIGNED_H_
// Memory allocator with support for alignment + misalignment.
#include <stddef.h>
#include <stdint.h>
#include <memory>
namespace jxl {
// Functions that depend on the cache line size.
class CacheAligned {
public:
static void PrintStats();
static constexpr size_t kPointerSize = sizeof(void*);
static constexpr size_t kCacheLineSize = 64;
// To avoid RFOs, match L2 fill size (pairs of lines).
static constexpr size_t kAlignment = 2 * kCacheLineSize;
// Minimum multiple for which cache set conflicts and/or loads blocked by
// preceding stores can occur.
static constexpr size_t kAlias = 2048;
// Returns a 'random' (cyclical) offset suitable for Allocate.
static size_t NextOffset();
// Returns null or memory whose address is congruent to `offset` (mod kAlias).
// This reduces cache conflicts and load/store stalls, especially with large
// allocations that would otherwise have similar alignments. At least
// `payload_size` (which can be zero) bytes will be accessible.
static void* Allocate(size_t payload_size, size_t offset);
static void* Allocate(const size_t payload_size) {
return Allocate(payload_size, NextOffset());
}
static void Free(const void* aligned_pointer);
};
// Avoids the need for a function pointer (deleter) in CacheAlignedUniquePtr.
struct CacheAlignedDeleter {
void operator()(uint8_t* aligned_pointer) const {
CacheAligned::Free(aligned_pointer);
}
};
using CacheAlignedUniquePtr = std::unique_ptr<uint8_t[], CacheAlignedDeleter>;
// Does not invoke constructors.
static inline CacheAlignedUniquePtr AllocateArray(const size_t bytes) {
return CacheAlignedUniquePtr(
static_cast<uint8_t*>(CacheAligned::Allocate(bytes)),
CacheAlignedDeleter());
}
} // namespace jxl
#endif // LIB_JXL_BASE_CACHE_ALIGNED_H_
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