iree/hal/buffer_view.c

// Copyright 2020 The IREE Authors
//
// Licensed under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#include "iree/hal/buffer_view.h"

#include <inttypes.h>
#include <stdbool.h>

#include "iree/base/api.h"
#include "iree/base/tracing.h"
#include "iree/hal/allocator.h"
#include "iree/hal/resource.h"
#include "iree/hal/string_util.h"

struct iree_hal_buffer_view_t {
  iree_atomic_ref_count_t ref_count;
  iree_hal_buffer_t* buffer;
  iree_hal_element_type_t element_type;
  iree_hal_encoding_type_t encoding_type;
  iree_device_size_t byte_length;
  iree_host_size_t shape_rank;
  iree_hal_dim_t shape[];
};

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_create(
    iree_hal_buffer_t* buffer, const iree_hal_dim_t* shape,
    iree_host_size_t shape_rank, iree_hal_element_type_t element_type,
    iree_hal_encoding_type_t encoding_type,
    iree_hal_buffer_view_t** out_buffer_view) {
  IREE_ASSERT_ARGUMENT(buffer);
  IREE_ASSERT_ARGUMENT(out_buffer_view);

  *out_buffer_view = NULL;
  if (IREE_UNLIKELY(shape_rank > 0 && !shape)) {
    return iree_make_status(IREE_STATUS_INVALID_ARGUMENT,
                            "no shape dimensions specified");
  }

  IREE_TRACE_ZONE_BEGIN(z0);

  iree_allocator_t host_allocator =
      iree_hal_allocator_host_allocator(iree_hal_buffer_allocator(buffer));

  // Allocate and initialize the iree_hal_buffer_view_t struct.
  // Note that we have the dynamically-sized shape dimensions on the end.
  iree_hal_buffer_view_t* buffer_view = NULL;
  iree_status_t status = iree_allocator_malloc(
      host_allocator,
      sizeof(*buffer_view) + sizeof(iree_hal_dim_t) * shape_rank,
      (void**)&buffer_view);
  if (iree_status_is_ok(status)) {
    iree_atomic_ref_count_init(&buffer_view->ref_count);
    buffer_view->buffer = buffer;
    iree_hal_buffer_retain(buffer_view->buffer);
    buffer_view->element_type = element_type;
    buffer_view->encoding_type = encoding_type;
    buffer_view->byte_length =
        iree_hal_element_byte_count(buffer_view->element_type);
    buffer_view->shape_rank = shape_rank;
    for (iree_host_size_t i = 0; i < shape_rank; ++i) {
      buffer_view->shape[i] = shape[i];
      buffer_view->byte_length *= shape[i];
    }
    *out_buffer_view = buffer_view;
  }

  IREE_TRACE_ZONE_END(z0);
  return status;
}

IREE_API_EXPORT void iree_hal_buffer_view_retain(
    iree_hal_buffer_view_t* buffer_view) {
  if (IREE_LIKELY(buffer_view)) {
    iree_atomic_ref_count_inc(&buffer_view->ref_count);
  }
}

IREE_API_EXPORT void iree_hal_buffer_view_release(
    iree_hal_buffer_view_t* buffer_view) {
  if (IREE_LIKELY(buffer_view) &&
      iree_atomic_ref_count_dec(&buffer_view->ref_count) == 1) {
    iree_hal_buffer_view_destroy(buffer_view);
  }
}

IREE_API_EXPORT void iree_hal_buffer_view_destroy(
    iree_hal_buffer_view_t* buffer_view) {
  iree_allocator_t host_allocator = iree_hal_allocator_host_allocator(
      iree_hal_buffer_allocator(buffer_view->buffer));
  iree_hal_buffer_release(buffer_view->buffer);
  iree_allocator_free(host_allocator, buffer_view);
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_allocate_buffer(
    iree_hal_allocator_t* allocator, const iree_hal_dim_t* shape,
    iree_host_size_t shape_rank, iree_hal_element_type_t element_type,
    iree_hal_encoding_type_t encoding_type, iree_hal_memory_type_t memory_type,
    iree_hal_buffer_usage_t allowed_usage,
    iree_hal_buffer_view_t** out_buffer_view) {
  IREE_ASSERT_ARGUMENT(allocator);
  IREE_ASSERT_ARGUMENT(out_buffer_view);
  IREE_TRACE_ZONE_BEGIN(z0);

  iree_device_size_t allocation_size = 0;
  iree_status_t status = iree_hal_buffer_compute_view_size(
      shape, shape_rank, element_type, encoding_type, &allocation_size);

  iree_hal_buffer_t* buffer = NULL;
  if (iree_status_is_ok(status)) {
    status = iree_hal_allocator_allocate_buffer(
        allocator, memory_type, allowed_usage, allocation_size, &buffer);
  }

  if (iree_status_is_ok(status)) {
    status =
        iree_hal_buffer_view_create(buffer, shape, shape_rank, element_type,
                                    encoding_type, out_buffer_view);
  }

  iree_hal_buffer_release(buffer);
  IREE_TRACE_ZONE_END(z0);
  return status;
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_clone_heap_buffer(
    iree_hal_allocator_t* allocator, const iree_hal_dim_t* shape,
    iree_host_size_t shape_rank, iree_hal_element_type_t element_type,
    iree_hal_encoding_type_t encoding_type, iree_hal_memory_type_t memory_type,
    iree_hal_buffer_usage_t allowed_usage, iree_const_byte_span_t data,
    iree_hal_buffer_view_t** out_buffer_view) {
  IREE_ASSERT_ARGUMENT(allocator);
  IREE_ASSERT_ARGUMENT(out_buffer_view);
  IREE_TRACE_ZONE_BEGIN(z0);

  // Allocate the buffer.
  iree_hal_buffer_view_t* buffer_view = NULL;
  IREE_RETURN_AND_END_ZONE_IF_ERROR(
      z0, iree_hal_buffer_view_allocate_buffer(
              allocator, shape, shape_rank, element_type, encoding_type,
              memory_type, allowed_usage, &buffer_view));

  // Copy all of the data into it in the worst way possible.
  // If you find yourself coming here from profiling:
  //   Don't clone data. Allocate and then populate it in-place.
  //   -or-
  //   Schedule sequences of DMA transfers using iree_hal_command_buffer_t.
  iree_status_t status = iree_hal_buffer_write_data(
      iree_hal_buffer_view_buffer(buffer_view), 0, data.data, data.data_length);

  if (iree_status_is_ok(status)) {
    *out_buffer_view = buffer_view;
  } else {
    iree_hal_buffer_view_release(buffer_view);
  }
  IREE_TRACE_ZONE_END(z0);
  return status;
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_wrap_heap_buffer(
    iree_hal_allocator_t* allocator, const iree_hal_dim_t* shape,
    iree_host_size_t shape_rank, iree_hal_element_type_t element_type,
    iree_hal_encoding_type_t encoding_type, iree_hal_memory_type_t memory_type,
    iree_hal_memory_access_t allowed_access,
    iree_hal_buffer_usage_t allowed_usage, iree_byte_span_t data,
    iree_allocator_t data_allocator, iree_hal_buffer_view_t** out_buffer_view) {
  IREE_ASSERT_ARGUMENT(allocator);
  IREE_ASSERT_ARGUMENT(out_buffer_view);
  IREE_TRACE_ZONE_BEGIN(z0);

  // NOTE: this will fail if the data cannot be imported into the allocator.
  iree_hal_buffer_t* buffer = NULL;
  iree_status_t status = iree_hal_allocator_wrap_buffer(
      allocator, memory_type, allowed_access, allowed_usage, data,
      data_allocator, &buffer);

  if (iree_status_is_ok(status)) {
    status =
        iree_hal_buffer_view_create(buffer, shape, shape_rank, element_type,
                                    encoding_type, out_buffer_view);
  }

  iree_hal_buffer_release(buffer);
  IREE_TRACE_ZONE_END(z0);
  return status;
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_wrap_or_clone_heap_buffer(
    iree_hal_allocator_t* allocator, const iree_hal_dim_t* shape,
    iree_host_size_t shape_rank, iree_hal_element_type_t element_type,
    iree_hal_encoding_type_t encoding_type, iree_hal_memory_type_t memory_type,
    iree_hal_memory_access_t allowed_access,
    iree_hal_buffer_usage_t allowed_usage, iree_byte_span_t data,
    iree_allocator_t data_allocator, iree_hal_buffer_view_t** out_buffer_view) {
  IREE_ASSERT_ARGUMENT(allocator);

  // Not all HAL implementations support wrapping buffers, and of those that do
  // some may only support it in special situations such as when the buffer is
  // not DEVICE_VISIBLE. The user application can query whether the wrapping is
  // possible and decide to use alternative means of upload if it is not; we
  // make no policy (other than validity) over what's best here.
  iree_hal_buffer_compatibility_t compatibility =
      iree_hal_allocator_query_buffer_compatibility(
          allocator, memory_type, allowed_usage, IREE_HAL_BUFFER_USAGE_MAPPING,
          (iree_device_size_t)data.data_length);
  bool wrap_allowed = iree_all_bits_set(
      compatibility, IREE_HAL_BUFFER_COMPATIBILITY_IMPORTABLE);
  if (wrap_allowed) {
    return iree_hal_buffer_view_wrap_heap_buffer(
        allocator, shape, shape_rank, element_type, encoding_type, memory_type,
        allowed_access, allowed_usage, data, data_allocator, out_buffer_view);
  } else {
    return iree_hal_buffer_view_clone_heap_buffer(
        allocator, shape, shape_rank, element_type, encoding_type, memory_type,
        allowed_usage, iree_make_const_byte_span(data.data, data.data_length),
        out_buffer_view);
  }
}

IREE_API_EXPORT iree_hal_buffer_t* iree_hal_buffer_view_buffer(
    const iree_hal_buffer_view_t* buffer_view) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  return buffer_view->buffer;
}

IREE_API_EXPORT iree_host_size_t
iree_hal_buffer_view_shape_rank(const iree_hal_buffer_view_t* buffer_view) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  return buffer_view->shape_rank;
}

IREE_API_EXPORT const iree_hal_dim_t* iree_hal_buffer_view_shape_dims(
    const iree_hal_buffer_view_t* buffer_view) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  return buffer_view->shape;
}

IREE_API_EXPORT iree_hal_dim_t iree_hal_buffer_view_shape_dim(
    const iree_hal_buffer_view_t* buffer_view, iree_host_size_t index) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  if (IREE_UNLIKELY(index > buffer_view->shape_rank)) {
    return 0;
  }
  return buffer_view->shape[index];
}

IREE_API_EXPORT iree_host_size_t
iree_hal_buffer_view_element_count(const iree_hal_buffer_view_t* buffer_view) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  iree_host_size_t element_count = 1;
  for (iree_host_size_t i = 0; i < buffer_view->shape_rank; ++i) {
    element_count *= buffer_view->shape[i];
  }
  return element_count;
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_shape(
    const iree_hal_buffer_view_t* buffer_view, iree_host_size_t rank_capacity,
    iree_hal_dim_t* out_shape, iree_host_size_t* out_shape_rank) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  IREE_ASSERT_ARGUMENT(out_shape);
  if (out_shape_rank) {
    *out_shape_rank = 0;
  }

  if (out_shape_rank) {
    *out_shape_rank = buffer_view->shape_rank;
  }
  if (rank_capacity < buffer_view->shape_rank) {
    // Not an error; just a size query.
    return iree_status_from_code(IREE_STATUS_OUT_OF_RANGE);
  }

  for (iree_host_size_t i = 0; i < buffer_view->shape_rank; ++i) {
    out_shape[i] = buffer_view->shape[i];
  }

  return iree_ok_status();
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_reshape(
    iree_hal_buffer_view_t* buffer_view, const iree_hal_dim_t* shape,
    iree_host_size_t shape_rank) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  IREE_ASSERT_ARGUMENT(shape);

  if (shape_rank != buffer_view->shape_rank) {
    return iree_make_status(IREE_STATUS_INVALID_ARGUMENT,
                            "buffer view reshapes must have the same rank; "
                            "target=%zu, existing=%zu",
                            shape_rank, buffer_view->shape_rank);
  }

  iree_device_size_t new_element_count = 1;
  for (iree_host_size_t i = 0; i < shape_rank; ++i) {
    new_element_count *= shape[i];
  }
  iree_device_size_t old_element_count =
      iree_hal_buffer_view_element_count(buffer_view);
  if (new_element_count != old_element_count) {
    return iree_make_status(IREE_STATUS_INVALID_ARGUMENT,
                            "buffer view reshapes must have the same element "
                            "count; target=%" PRIdsz ", existing=%" PRIdsz,
                            new_element_count, old_element_count);
  }

  for (iree_host_size_t i = 0; i < shape_rank; ++i) {
    buffer_view->shape[i] = shape[i];
  }

  return iree_ok_status();
}

IREE_API_EXPORT iree_hal_element_type_t
iree_hal_buffer_view_element_type(const iree_hal_buffer_view_t* buffer_view) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  return buffer_view->element_type;
}

IREE_API_EXPORT iree_host_size_t
iree_hal_buffer_view_element_size(const iree_hal_buffer_view_t* buffer_view) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  return iree_hal_element_byte_count(buffer_view->element_type);
}

IREE_API_EXPORT iree_hal_encoding_type_t
iree_hal_buffer_view_encoding_type(const iree_hal_buffer_view_t* buffer_view) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  return buffer_view->encoding_type;
}

IREE_API_EXPORT iree_device_size_t
iree_hal_buffer_view_byte_length(const iree_hal_buffer_view_t* buffer_view) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  return buffer_view->byte_length;
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_compute_offset(
    const iree_hal_buffer_view_t* buffer_view, const iree_hal_dim_t* indices,
    iree_host_size_t indices_count, iree_device_size_t* out_offset) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  return iree_hal_buffer_compute_view_offset(
      buffer_view->shape, buffer_view->shape_rank, buffer_view->element_type,
      buffer_view->encoding_type, indices, indices_count, out_offset);
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_compute_range(
    const iree_hal_buffer_view_t* buffer_view,
    const iree_hal_dim_t* start_indices, iree_host_size_t indices_count,
    const iree_hal_dim_t* lengths, iree_host_size_t lengths_count,
    iree_device_size_t* out_start_offset, iree_device_size_t* out_length) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  return iree_hal_buffer_compute_view_range(
      buffer_view->shape, buffer_view->shape_rank, buffer_view->element_type,
      buffer_view->encoding_type, start_indices, indices_count, lengths,
      lengths_count, out_start_offset, out_length);
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_compute_view_size(
    const iree_hal_dim_t* shape, iree_host_size_t shape_rank,
    iree_hal_element_type_t element_type,
    iree_hal_encoding_type_t encoding_type,
    iree_device_size_t* out_allocation_size) {
  IREE_ASSERT_ARGUMENT(shape);
  IREE_ASSERT_ARGUMENT(out_allocation_size);
  *out_allocation_size = 0;

  iree_device_size_t byte_length = 0;

  switch (encoding_type) {
    case IREE_HAL_ENCODING_TYPE_DENSE_ROW_MAJOR:
      byte_length = iree_hal_element_byte_count(element_type);
      for (iree_host_size_t i = 0; i < shape_rank; ++i) {
        byte_length *= shape[i];
      }
      break;
    default:
      return iree_make_status(IREE_STATUS_UNIMPLEMENTED,
                              "unimplemented encoding type size calculation");
  }

  *out_allocation_size = byte_length;
  return iree_ok_status();
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_compute_view_offset(
    const iree_hal_dim_t* shape, iree_host_size_t shape_rank,
    iree_hal_element_type_t element_type,
    iree_hal_encoding_type_t encoding_type, const iree_hal_dim_t* indices,
    iree_host_size_t indices_count, iree_device_size_t* out_offset) {
  IREE_ASSERT_ARGUMENT(shape);
  IREE_ASSERT_ARGUMENT(indices);
  IREE_ASSERT_ARGUMENT(out_offset);
  *out_offset = 0;
  if (encoding_type != IREE_HAL_ENCODING_TYPE_DENSE_ROW_MAJOR) {
    return iree_make_status(
        IREE_STATUS_INVALID_ARGUMENT,
        "only dense encodings support view range computation");
  }
  if (IREE_UNLIKELY(shape_rank != indices_count)) {
    return iree_make_status(IREE_STATUS_INVALID_ARGUMENT,
                            "shape rank/indices mismatch: %zu != %zu",
                            shape_rank, indices_count);
  }

  iree_device_size_t offset = 0;
  for (iree_host_size_t i = 0; i < indices_count; ++i) {
    if (IREE_UNLIKELY(indices[i] >= shape[i])) {
      return iree_make_status(IREE_STATUS_OUT_OF_RANGE,
                              "index[%zu] out of bounds: %d >= %d", i,
                              indices[i], shape[i]);
    }
    iree_device_size_t axis_offset = indices[i];
    for (iree_host_size_t j = i + 1; j < shape_rank; ++j) {
      axis_offset *= shape[j];
    }
    offset += axis_offset;
  }
  offset *= iree_hal_element_byte_count(element_type);

  *out_offset = offset;
  return iree_ok_status();
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_compute_view_range(
    const iree_hal_dim_t* shape, iree_host_size_t shape_rank,
    iree_hal_element_type_t element_type,
    iree_hal_encoding_type_t encoding_type, const iree_hal_dim_t* start_indices,
    iree_host_size_t indices_count, const iree_hal_dim_t* lengths,
    iree_host_size_t lengths_count, iree_device_size_t* out_start_offset,
    iree_device_size_t* out_length) {
  IREE_ASSERT_ARGUMENT(shape);
  IREE_ASSERT_ARGUMENT(start_indices);
  IREE_ASSERT_ARGUMENT(lengths);
  IREE_ASSERT_ARGUMENT(out_start_offset);
  IREE_ASSERT_ARGUMENT(out_length);
  *out_start_offset = 0;
  *out_length = 0;
  if (encoding_type != IREE_HAL_ENCODING_TYPE_DENSE_ROW_MAJOR) {
    return iree_make_status(
        IREE_STATUS_INVALID_ARGUMENT,
        "only dense encodings support view range computation");
  }
  if (IREE_UNLIKELY(indices_count != lengths_count)) {
    return iree_make_status(IREE_STATUS_INVALID_ARGUMENT,
                            "indices/lengths mismatch: %zu != %zu",
                            indices_count, lengths_count);
  }
  if (IREE_UNLIKELY(shape_rank != indices_count)) {
    return iree_make_status(IREE_STATUS_INVALID_ARGUMENT,
                            "shape rank/indices mismatch: %zu != %zu",
                            shape_rank, indices_count);
  }

  iree_hal_dim_t* end_indices =
      iree_alloca(shape_rank * sizeof(iree_hal_dim_t));
  iree_device_size_t element_size = iree_hal_element_byte_count(element_type);
  iree_device_size_t subspan_length = element_size;
  for (iree_host_size_t i = 0; i < lengths_count; ++i) {
    subspan_length *= lengths[i];
    end_indices[i] = start_indices[i] + lengths[i] - 1;
  }

  iree_device_size_t start_byte_offset = 0;
  IREE_RETURN_IF_ERROR(iree_hal_buffer_compute_view_offset(
      shape, shape_rank, element_type, encoding_type, start_indices,
      indices_count, &start_byte_offset));
  iree_device_size_t end_byte_offset = 0;
  IREE_RETURN_IF_ERROR(iree_hal_buffer_compute_view_offset(
      shape, shape_rank, element_type, encoding_type, end_indices, shape_rank,
      &end_byte_offset));

  // Non-contiguous regions not yet implemented. Will be easier to detect when
  // we have strides.
  iree_device_size_t offset_length =
      end_byte_offset - start_byte_offset + element_size;
  if (subspan_length != offset_length) {
    return iree_make_status(
        IREE_STATUS_UNIMPLEMENTED,
        "non-contiguous range region computation not implemented");
  }

  *out_start_offset = start_byte_offset;
  *out_length = subspan_length;
  return iree_ok_status();
}

static iree_status_t iree_hal_buffer_view_parse_impl(
    iree_string_view_t value, iree_hal_allocator_t* buffer_allocator,
    iree_hal_buffer_view_t** out_buffer_view) {
  // Strip whitespace that may come along (linefeeds/etc).
  value = iree_string_view_trim(value);
  value = iree_string_view_strip_prefix(value, IREE_SV("\""));
  value = iree_string_view_strip_suffix(value, IREE_SV("\""));
  if (iree_string_view_is_empty(value)) {
    // Empty lines are invalid; need at least the shape/type information.
    *out_buffer_view = NULL;
    return iree_make_status(IREE_STATUS_INVALID_ARGUMENT, "empty string input");
  }

  // The part of the string corresponding to the shape, e.g. 1x2x3.
  iree_string_view_t shape_str = iree_string_view_empty();
  // The part of the string corresponding to the type, e.g. f32
  iree_string_view_t type_str = iree_string_view_empty();
  // The part of the string corresponding to the buffer data, e.g. 1 2 3 4 5 6
  iree_string_view_t data_str = iree_string_view_empty();

  iree_string_view_t shape_and_type_str = value;
  iree_string_view_split(value, '=', &shape_and_type_str, &data_str);
  iree_host_size_t last_x_index = iree_string_view_find_last_of(
      shape_and_type_str, IREE_SV("x"), IREE_STRING_VIEW_NPOS);
  if (last_x_index == IREE_STRING_VIEW_NPOS) {
    // Scalar.
    type_str = shape_and_type_str;
  } else {
    // Has a shape.
    shape_str = iree_string_view_substr(shape_and_type_str, 0, last_x_index);
    type_str = iree_string_view_substr(shape_and_type_str, last_x_index + 1,
                                       IREE_STRING_VIEW_NPOS);
  }

  // AxBxC...
  iree_host_size_t shape_rank = 0;
  iree_status_t shape_result =
      iree_hal_parse_shape(shape_str, 0, NULL, &shape_rank);
  if (!iree_status_is_ok(shape_result) &&
      !iree_status_is_out_of_range(shape_result)) {
    return shape_result;
  } else if (shape_rank > 128) {
    return iree_make_status(
        IREE_STATUS_RESOURCE_EXHAUSTED,
        "a shape rank of %zu is just a little bit excessive, eh?", shape_rank);
  }
  shape_result = iree_status_ignore(shape_result);
  iree_hal_dim_t* shape =
      (iree_hal_dim_t*)iree_alloca(shape_rank * sizeof(iree_hal_dim_t));
  IREE_RETURN_IF_ERROR(
      iree_hal_parse_shape(shape_str, shape_rank, shape, &shape_rank));

  // f32, i32, etc
  iree_hal_element_type_t element_type = IREE_HAL_ELEMENT_TYPE_NONE;
  IREE_RETURN_IF_ERROR(iree_hal_parse_element_type(type_str, &element_type));

  // TODO(benvanik): allow specifying the encoding.
  iree_hal_encoding_type_t encoding_type =
      IREE_HAL_ENCODING_TYPE_DENSE_ROW_MAJOR;

  // Allocate the buffer we will parse into from the provided allocator.
  iree_device_size_t buffer_length = 0;
  IREE_RETURN_IF_ERROR(iree_hal_buffer_compute_view_size(
      shape, shape_rank, element_type, encoding_type, &buffer_length));
  iree_hal_buffer_t* buffer = NULL;
  IREE_RETURN_IF_ERROR(iree_hal_allocator_allocate_buffer(
      buffer_allocator,
      IREE_HAL_MEMORY_TYPE_HOST_LOCAL | IREE_HAL_MEMORY_TYPE_DEVICE_VISIBLE,
      IREE_HAL_BUFFER_USAGE_TRANSFER | IREE_HAL_BUFFER_USAGE_MAPPING |
          IREE_HAL_BUFFER_USAGE_DISPATCH,
      buffer_length, &buffer));

  // Parse the elements directly into the buffer.
  iree_hal_buffer_mapping_t buffer_mapping;
  iree_status_t status =
      iree_hal_buffer_map_range(buffer, IREE_HAL_MEMORY_ACCESS_DISCARD_WRITE, 0,
                                buffer_length, &buffer_mapping);
  if (!iree_status_is_ok(status)) {
    iree_hal_buffer_release(buffer);
    return status;
  }
  status = iree_hal_parse_buffer_elements(data_str, element_type,
                                          buffer_mapping.contents);
  iree_hal_buffer_unmap_range(&buffer_mapping);
  if (!iree_status_is_ok(status)) {
    iree_hal_buffer_release(buffer);
    return status;
  }

  // Wrap and pass ownership of the buffer to the buffer view.
  status = iree_hal_buffer_view_create(buffer, shape, shape_rank, element_type,
                                       encoding_type, out_buffer_view);
  iree_hal_buffer_release(buffer);
  return status;
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_parse(
    iree_string_view_t value, iree_hal_allocator_t* buffer_allocator,
    iree_hal_buffer_view_t** out_buffer_view) {
  IREE_ASSERT_ARGUMENT(buffer_allocator);
  IREE_ASSERT_ARGUMENT(out_buffer_view);
  *out_buffer_view = NULL;
  IREE_TRACE_ZONE_BEGIN(z0);
  iree_status_t status =
      iree_hal_buffer_view_parse_impl(value, buffer_allocator, out_buffer_view);
  IREE_TRACE_ZONE_END(z0);
  return status;
}

#define APPEND_CHAR(c)                           \
  {                                              \
    if (buffer) {                                \
      if (buffer_length < buffer_capacity - 1) { \
        buffer[buffer_length] = c;               \
        buffer[buffer_length + 1] = '\0';        \
      } else {                                   \
        buffer = NULL;                           \
      }                                          \
    }                                            \
    ++buffer_length;                             \
  }

static iree_status_t iree_hal_buffer_view_format_impl(
    const iree_hal_buffer_view_t* buffer_view,
    iree_host_size_t max_element_count, iree_host_size_t buffer_capacity,
    char* buffer, iree_host_size_t* out_buffer_length) {
  if (out_buffer_length) {
    *out_buffer_length = 0;
  }
  if (buffer && buffer_capacity) {
    buffer[0] = 0;
  }

  iree_host_size_t buffer_length = 0;
  if (iree_hal_buffer_view_shape_rank(buffer_view) > 0) {
    // Shape: 1x2x3
    iree_host_size_t shape_length = 0;
    iree_status_t status = iree_hal_format_shape(
        iree_hal_buffer_view_shape_dims(buffer_view),
        iree_hal_buffer_view_shape_rank(buffer_view),
        buffer ? buffer_capacity - buffer_length : 0,
        buffer ? buffer + buffer_length : NULL, &shape_length);
    buffer_length += shape_length;
    if (iree_status_is_out_of_range(status)) {
      status = iree_status_ignore(status);
      buffer = NULL;
    } else if (!iree_status_is_ok(status)) {
      return status;
    }

    // Separator: <shape>x<format>
    APPEND_CHAR('x');
  }

  // Element type: f32
  iree_host_size_t element_type_length = 0;
  iree_status_t status = iree_hal_format_element_type(
      iree_hal_buffer_view_element_type(buffer_view),
      buffer ? buffer_capacity - buffer_length : 0,
      buffer ? buffer + buffer_length : NULL, &element_type_length);
  buffer_length += element_type_length;
  if (iree_status_is_out_of_range(status)) {
    status = iree_status_ignore(status);
    buffer = NULL;
  } else if (!iree_status_is_ok(status)) {
    return status;
  }

  // TODO(benvanik): allow printing the encoding.

  // Separator: <meta>=<value>
  APPEND_CHAR('=');

  // Buffer contents: 0 1 2 3 ...
  iree_hal_buffer_mapping_t buffer_mapping;
  IREE_RETURN_IF_ERROR(iree_hal_buffer_map_range(
      iree_hal_buffer_view_buffer(buffer_view), IREE_HAL_MEMORY_ACCESS_READ, 0,
      IREE_WHOLE_BUFFER, &buffer_mapping));
  iree_host_size_t elements_length = 0;
  status = iree_hal_format_buffer_elements(
      iree_make_const_byte_span(buffer_mapping.contents.data,
                                buffer_mapping.contents.data_length),
      iree_hal_buffer_view_shape_dims(buffer_view),
      iree_hal_buffer_view_shape_rank(buffer_view),
      iree_hal_buffer_view_element_type(buffer_view), max_element_count,
      buffer ? buffer_capacity - buffer_length : 0,
      buffer ? buffer + buffer_length : NULL, &elements_length);
  buffer_length += elements_length;
  iree_hal_buffer_unmap_range(&buffer_mapping);
  if (iree_status_is_out_of_range(status)) {
    status = iree_status_ignore(status);
    buffer = NULL;
  } else if (!iree_status_is_ok(status)) {
    return status;
  }

  if (out_buffer_length) {
    *out_buffer_length = buffer_length;
  }
  return buffer ? iree_ok_status()
                : iree_status_from_code(IREE_STATUS_OUT_OF_RANGE);
}

IREE_API_EXPORT iree_status_t iree_hal_buffer_view_format(
    const iree_hal_buffer_view_t* buffer_view,
    iree_host_size_t max_element_count, iree_host_size_t buffer_capacity,
    char* buffer, iree_host_size_t* out_buffer_length) {
  IREE_ASSERT_ARGUMENT(buffer_view);
  IREE_TRACE_ZONE_BEGIN(z0);
  iree_status_t status = iree_hal_buffer_view_format_impl(
      buffer_view, max_element_count, buffer_capacity, buffer,
      out_buffer_length);
  IREE_TRACE_ZONE_END(z0);
  return status;
}

// TODO(benvanik): streaming all the way down (needs string_util updates).
IREE_API_EXPORT iree_status_t iree_hal_buffer_view_fprint(
    FILE* file, const iree_hal_buffer_view_t* buffer_view,
    iree_host_size_t max_element_count) {
  IREE_ASSERT_ARGUMENT(file);
  IREE_ASSERT_ARGUMENT(buffer_view);
  IREE_TRACE_ZONE_BEGIN(z0);

  // Query the string length (in characters).
  iree_host_size_t buffer_length = 0;
  iree_status_t status = iree_hal_buffer_view_format(
      buffer_view, max_element_count, 0, NULL, &buffer_length);
  if (!iree_status_is_out_of_range(status)) {
    IREE_TRACE_ZONE_END(z0);
    return status;
  }

  // Allocate scratch space to format in to.
  // We should be streaming.
  iree_allocator_t host_allocator = iree_hal_allocator_host_allocator(
      iree_hal_buffer_allocator(iree_hal_buffer_view_buffer(buffer_view)));
  iree_host_size_t buffer_capacity = buffer_length + 1;  // NUL
  char* buffer = NULL;
  status =
      iree_allocator_malloc(host_allocator, buffer_capacity, (void**)&buffer);

  // Format the buffer into the string storage.
  if (iree_status_is_ok(status)) {
    status =
        iree_hal_buffer_view_format(buffer_view, max_element_count,
                                    buffer_capacity, buffer, &buffer_length);
  }

  // Dump to the file.
  if (iree_status_is_ok(status)) {
    fprintf(file, "%.*s", (int)buffer_length, buffer);
  }

  iree_allocator_free(host_allocator, buffer);
  IREE_TRACE_ZONE_END(z0);
  return status;
}