// 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.

#include "lib/jxl/simd_util.h"

#include <algorithm>
#include <cstddef>

#undef HWY_TARGET_INCLUDE
#define HWY_TARGET_INCLUDE "lib/jxl/simd_util.cc"
#include <hwy/foreach_target.h>
#include <hwy/highway.h>

#include "lib/jxl/base/common.h"
#include "lib/jxl/base/status.h"
#include "lib/jxl/cache_aligned.h"

HWY_BEFORE_NAMESPACE();
namespace jxl {
namespace HWY_NAMESPACE {

size_t MaxVectorSize() {
  HWY_FULL(float) df;
  return Lanes(df) * sizeof(float);
}

// NOLINTNEXTLINE(google-readability-namespace-comments)
}  // namespace HWY_NAMESPACE
}  // namespace jxl
HWY_AFTER_NAMESPACE();

#if HWY_ONCE
namespace jxl {

HWY_EXPORT(MaxVectorSize);

size_t MaxVectorSize() {
  // Ideally HWY framework should provide us this value.
  // Less than ideal is to check all available targets and choose maximal.
  // As for now, we just ask current active target, assuming it won't change.
  return HWY_DYNAMIC_DISPATCH(MaxVectorSize)();
}

size_t BytesPerRow(const size_t xsize, const size_t sizeof_t) {
  // Special case: we don't allow any ops -> don't need extra padding/
  if (xsize == 0) {
    return 0;
  }

  const size_t vec_size = MaxVectorSize();
  size_t valid_bytes = xsize * sizeof_t;

  // Allow unaligned accesses starting at the last valid value.
  // Skip for the scalar case because no extra lanes will be loaded.
  if (vec_size != 0) {
    valid_bytes += vec_size - sizeof_t;
  }

  // Round up to vector and cache line size.
  const size_t align = std::max(vec_size, CacheAligned::kAlignment);
  size_t bytes_per_row = RoundUpTo(valid_bytes, align);

  // During the lengthy window before writes are committed to memory, CPUs
  // guard against read after write hazards by checking the address, but
  // only the lower 11 bits. We avoid a false dependency between writes to
  // consecutive rows by ensuring their sizes are not multiples of 2 KiB.
  // Avoid2K prevents the same problem for the planes of an Image3.
  if (bytes_per_row % CacheAligned::kAlias == 0) {
    bytes_per_row += align;
  }

  JXL_ASSERT(bytes_per_row % align == 0);
  return bytes_per_row;
}

}  // namespace jxl
#endif