/** \file
 * \ingroup gpu
 */

#include "BLI_math_base.h"
#include "BLI_math_bits.h"

#include "GPU_framebuffer.h"

#include "mtl_context.hh"
#include "mtl_framebuffer.hh"
#include "mtl_state.hh"

namespace blender::gpu {

/* -------------------------------------------------------------------- */
/** \name MTLStateManager
 * \{ */

void MTLStateManager::mtl_state_init(void)
{
  BLI_assert(context_);
  context_->pipeline_state_init();
}

MTLStateManager::MTLStateManager(MTLContext *ctx) : StateManager()
{
  /* Initialize State. */
  context_ = ctx;
  mtl_state_init();

  /* Force update using default state. */
  current_ = ~state;
  current_mutable_ = ~mutable_state;
  set_state(state);
  set_mutable_state(mutable_state);
}

void MTLStateManager::apply_state(void)
{
  this->set_state(this->state);
  this->set_mutable_state(this->mutable_state);

  /* Apply active FrameBuffer state. */
  static_cast<MTLFrameBuffer *>(context_->active_fb)->apply_state();
};

void MTLStateManager::force_state(void)
{
  /* Little exception for clip distances since they need to keep the old count correct. */
  uint32_t clip_distances = current_.clip_distances;
  current_ = ~this->state;
  current_.clip_distances = clip_distances;
  current_mutable_ = ~this->mutable_state;
  this->set_state(this->state);
  this->set_mutable_state(this->mutable_state);
};

void MTLStateManager::set_state(const GPUState &state)
{
  GPUState changed = state ^ current_;

  if (changed.blend != 0) {
    set_blend((eGPUBlend)state.blend);
  }
  if (changed.write_mask != 0) {
    set_write_mask((eGPUWriteMask)state.write_mask);
  }
  if (changed.depth_test != 0) {
    set_depth_test((eGPUDepthTest)state.depth_test);
  }
  if (changed.stencil_test != 0 || changed.stencil_op != 0) {
    set_stencil_test((eGPUStencilTest)state.stencil_test, (eGPUStencilOp)state.stencil_op);
    set_stencil_mask((eGPUStencilTest)state.stencil_test, mutable_state);
  }
  if (changed.clip_distances != 0) {
    set_clip_distances(state.clip_distances, current_.clip_distances);
  }
  if (changed.culling_test != 0) {
    set_backface_culling((eGPUFaceCullTest)state.culling_test);
  }
  if (changed.logic_op_xor != 0) {
    set_logic_op(state.logic_op_xor);
  }
  if (changed.invert_facing != 0) {
    set_facing(state.invert_facing);
  }
  if (changed.provoking_vert != 0) {
    set_provoking_vert((eGPUProvokingVertex)state.provoking_vert);
  }
  if (changed.shadow_bias != 0) {
    set_shadow_bias(state.shadow_bias);
  }

  /* TODO remove (Following GLState). */
  if (changed.polygon_smooth) {
    /* NOTE: Unsupported in Metal. */
  }
  if (changed.line_smooth) {
    /* NOTE: Unsupported in Metal. */
  }

  current_ = state;
}

void MTLStateManager::mtl_depth_range(float near, float far)
{
  BLI_assert(context_);
  BLI_assert(near >= 0.0 && near < 1.0);
  BLI_assert(far > 0.0 && far <= 1.0);
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;
  MTLContextDepthStencilState &ds_state = pipeline_state.depth_stencil_state;

  ds_state.depth_range_near = near;
  ds_state.depth_range_far = far;
  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_VIEWPORT_FLAG;
}

void MTLStateManager::set_mutable_state(const GPUStateMutable &state)
{
  GPUStateMutable changed = state ^ current_mutable_;
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;

  if (float_as_uint(changed.point_size) != 0) {
    pipeline_state.point_size = state.point_size;
    pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_PSO_FLAG;
  }

  if (changed.line_width != 0) {
    pipeline_state.line_width = state.line_width;
    pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_PSO_FLAG;
  }

  if (changed.depth_range[0] != 0 || changed.depth_range[1] != 0) {
    /* TODO remove, should modify the projection matrix instead. */
    mtl_depth_range(state.depth_range[0], state.depth_range[1]);
  }

  if (changed.stencil_compare_mask != 0 || changed.stencil_reference != 0 ||
      changed.stencil_write_mask != 0) {
    set_stencil_mask((eGPUStencilTest)current_.stencil_test, state);
  }

  current_mutable_ = state;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name State setting functions
 * \{ */

void MTLStateManager::set_write_mask(const eGPUWriteMask value)
{
  BLI_assert(context_);
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;
  pipeline_state.depth_stencil_state.depth_write_enable = ((value & GPU_WRITE_DEPTH) != 0);
  pipeline_state.color_write_mask =
      (((value & GPU_WRITE_RED) != 0) ? MTLColorWriteMaskRed : MTLColorWriteMaskNone) |
      (((value & GPU_WRITE_GREEN) != 0) ? MTLColorWriteMaskGreen : MTLColorWriteMaskNone) |
      (((value & GPU_WRITE_BLUE) != 0) ? MTLColorWriteMaskBlue : MTLColorWriteMaskNone) |
      (((value & GPU_WRITE_ALPHA) != 0) ? MTLColorWriteMaskAlpha : MTLColorWriteMaskNone);
  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_PSO_FLAG;
}

static MTLCompareFunction gpu_depth_function_to_metal(eGPUDepthTest depth_func)
{
  switch (depth_func) {
    case GPU_DEPTH_NONE:
      return MTLCompareFunctionNever;
    case GPU_DEPTH_LESS:
      return MTLCompareFunctionLess;
    case GPU_DEPTH_EQUAL:
      return MTLCompareFunctionEqual;
    case GPU_DEPTH_LESS_EQUAL:
      return MTLCompareFunctionLessEqual;
    case GPU_DEPTH_GREATER:
      return MTLCompareFunctionGreater;
    case GPU_DEPTH_GREATER_EQUAL:
      return MTLCompareFunctionGreaterEqual;
    case GPU_DEPTH_ALWAYS:
      return MTLCompareFunctionAlways;
    default:
      BLI_assert(false && "Invalid eGPUDepthTest");
      break;
  }
  return MTLCompareFunctionAlways;
}

static MTLCompareFunction gpu_stencil_func_to_metal(eGPUStencilTest stencil_func)
{
  switch (stencil_func) {
    case GPU_STENCIL_NONE:
      return MTLCompareFunctionAlways;
    case GPU_STENCIL_EQUAL:
      return MTLCompareFunctionEqual;
    case GPU_STENCIL_NEQUAL:
      return MTLCompareFunctionNotEqual;
    case GPU_STENCIL_ALWAYS:
      return MTLCompareFunctionAlways;
    default:
      BLI_assert(false && "Unrecognised eGPUStencilTest function");
      break;
  }
  return MTLCompareFunctionAlways;
}

void MTLStateManager::set_depth_test(const eGPUDepthTest value)
{
  BLI_assert(context_);
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;
  MTLContextDepthStencilState &ds_state = pipeline_state.depth_stencil_state;

  ds_state.depth_test_enabled = (value != GPU_DEPTH_NONE);
  ds_state.depth_function = gpu_depth_function_to_metal(value);
  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_DEPTHSTENCIL_FLAG;
}

void MTLStateManager::mtl_stencil_mask(uint mask)
{
  BLI_assert(context_);
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;
  pipeline_state.depth_stencil_state.stencil_write_mask = mask;
  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_DEPTHSTENCIL_FLAG;
}

void MTLStateManager::mtl_stencil_set_func(eGPUStencilTest stencil_func, int ref, uint mask)
{
  BLI_assert(context_);
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;
  MTLContextDepthStencilState &ds_state = pipeline_state.depth_stencil_state;

  ds_state.stencil_func = gpu_stencil_func_to_metal(stencil_func);
  ds_state.stencil_ref = ref;
  ds_state.stencil_read_mask = mask;
  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_DEPTHSTENCIL_FLAG;
}

static void mtl_stencil_set_op_separate(MTLContext *context,
                                        eGPUFaceCullTest face,
                                        MTLStencilOperation stencil_fail,
                                        MTLStencilOperation depth_test_fail,
                                        MTLStencilOperation depthstencil_pass)
{
  BLI_assert(context);
  MTLContextGlobalShaderPipelineState &pipeline_state = context->pipeline_state;
  MTLContextDepthStencilState &ds_state = pipeline_state.depth_stencil_state;

  if (face == GPU_CULL_FRONT) {
    ds_state.stencil_op_front_stencil_fail = stencil_fail;
    ds_state.stencil_op_front_depth_fail = depth_test_fail;
    ds_state.stencil_op_front_depthstencil_pass = depthstencil_pass;
  }
  else if (face == GPU_CULL_BACK) {
    ds_state.stencil_op_back_stencil_fail = stencil_fail;
    ds_state.stencil_op_back_depth_fail = depth_test_fail;
    ds_state.stencil_op_back_depthstencil_pass = depthstencil_pass;
  }

  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_DEPTHSTENCIL_FLAG;
}

static void mtl_stencil_set_op(MTLContext *context,
                               MTLStencilOperation stencil_fail,
                               MTLStencilOperation depth_test_fail,
                               MTLStencilOperation depthstencil_pass)
{
  mtl_stencil_set_op_separate(
      context, GPU_CULL_FRONT, stencil_fail, depth_test_fail, depthstencil_pass);
  mtl_stencil_set_op_separate(
      context, GPU_CULL_BACK, stencil_fail, depth_test_fail, depthstencil_pass);
}

void MTLStateManager::set_stencil_test(const eGPUStencilTest test, const eGPUStencilOp operation)
{
  switch (operation) {
    case GPU_STENCIL_OP_REPLACE:
      mtl_stencil_set_op(
          context_, MTLStencilOperationKeep, MTLStencilOperationKeep, MTLStencilOperationReplace);
      break;
    case GPU_STENCIL_OP_COUNT_DEPTH_PASS:
      /* Winding inversed due to flipped Y coordinate system in Metal. */
      mtl_stencil_set_op_separate(context_,
                                  GPU_CULL_FRONT,
                                  MTLStencilOperationKeep,
                                  MTLStencilOperationKeep,
                                  MTLStencilOperationIncrementWrap);
      mtl_stencil_set_op_separate(context_,
                                  GPU_CULL_BACK,
                                  MTLStencilOperationKeep,
                                  MTLStencilOperationKeep,
                                  MTLStencilOperationDecrementWrap);
      break;
    case GPU_STENCIL_OP_COUNT_DEPTH_FAIL:
      /* Winding inversed due to flipped Y coordinate system in Metal. */
      mtl_stencil_set_op_separate(context_,
                                  GPU_CULL_FRONT,
                                  MTLStencilOperationKeep,
                                  MTLStencilOperationDecrementWrap,
                                  MTLStencilOperationKeep);
      mtl_stencil_set_op_separate(context_,
                                  GPU_CULL_BACK,
                                  MTLStencilOperationKeep,
                                  MTLStencilOperationIncrementWrap,
                                  MTLStencilOperationKeep);
      break;
    case GPU_STENCIL_OP_NONE:
    default:
      mtl_stencil_set_op(
          context_, MTLStencilOperationKeep, MTLStencilOperationKeep, MTLStencilOperationKeep);
  }

  BLI_assert(context_);
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;
  pipeline_state.depth_stencil_state.stencil_test_enabled = (test != GPU_STENCIL_NONE);
  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_DEPTHSTENCIL_FLAG;
}

void MTLStateManager::set_stencil_mask(const eGPUStencilTest test, const GPUStateMutable state)
{
  if (test == GPU_STENCIL_NONE) {
    mtl_stencil_mask(0x00);
    mtl_stencil_set_func(GPU_STENCIL_ALWAYS, 0x00, 0x00);
  }
  else {
    mtl_stencil_mask(state.stencil_write_mask);
    mtl_stencil_set_func(test, state.stencil_reference, state.stencil_compare_mask);
  }
}

void MTLStateManager::set_clip_distances(const int new_dist_len, const int old_dist_len)
{
  /* TODO(Metal): Support Clip distances in METAL. Clip distance
   * assignment via shader is supported, but global clip-states require
   * support. */
}

void MTLStateManager::set_logic_op(const bool enable)
{
  /* NOTE(Metal): Logic Operations not directly supported. */
}

void MTLStateManager::set_facing(const bool invert)
{
  /* Check Current Context. */
  BLI_assert(context_);
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;

  /* Apply State -- opposite of GL, as METAL default is GPU_CLOCKWISE, GL default is
   * COUNTERCLOCKWISE. This needs to be the inverse of the default. */
  pipeline_state.front_face = (invert) ? GPU_COUNTERCLOCKWISE : GPU_CLOCKWISE;

  /* Mark Dirty - Ensure context updates state between draws. */
  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_FRONT_FACING_FLAG;
  pipeline_state.dirty = true;
}

void MTLStateManager::set_backface_culling(const eGPUFaceCullTest test)
{
  /* Check Current Context. */
  BLI_assert(context_);
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;

  /* Apply State. */
  pipeline_state.culling_enabled = (test != GPU_CULL_NONE);
  pipeline_state.cull_mode = test;

  /* Mark Dirty - Ensure context updates state between draws. */
  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_CULLMODE_FLAG;
  pipeline_state.dirty = true;
}

void MTLStateManager::set_provoking_vert(const eGPUProvokingVertex vert)
{
  /* NOTE(Metal): Provoking vertex is not a feature in the Metal API.
   * Shaders are handled on a case-by-case basis using a modified vertex shader.
   * For example, wireframe rendering and edit-mesh shaders utilize an SSBO-based
   * vertex fetching mechanism which considers the inverse convention for flat
   * shading, to ensure consistent results with OpenGL. */
}

void MTLStateManager::set_shadow_bias(const bool enable)
{
  /* Check Current Context. */
  BLI_assert(context_);
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;
  MTLContextDepthStencilState &ds_state = pipeline_state.depth_stencil_state;

  /* Apply State. */
  if (enable) {
    ds_state.depth_bias_enabled_for_lines = true;
    ds_state.depth_bias_enabled_for_tris = true;
    ds_state.depth_bias = 2.0f;
    ds_state.depth_slope_scale = 1.0f;
  }
  else {
    ds_state.depth_bias_enabled_for_lines = false;
    ds_state.depth_bias_enabled_for_tris = false;
    ds_state.depth_bias = 0.0f;
    ds_state.depth_slope_scale = 0.0f;
  }

  /* Mark Dirty - Ensure context updates depth-stencil state between draws. */
  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_DEPTHSTENCIL_FLAG;
  pipeline_state.dirty = true;
}

void MTLStateManager::set_blend(const eGPUBlend value)
{
  /**
   * Factors to the equation.
   * SRC is fragment shader output.
   * DST is framebuffer color.
   * final.rgb = SRC.rgb * src_rgb + DST.rgb * dst_rgb;
   * final.a = SRC.a * src_alpha + DST.a * dst_alpha;
   **/
  MTLBlendFactor src_rgb;
  MTLBlendFactor dst_rgb;
  MTLBlendFactor src_alpha;
  MTLBlendFactor dst_alpha;
  switch (value) {
    default:
    case GPU_BLEND_ALPHA: {
      src_rgb = MTLBlendFactorSourceAlpha;
      dst_rgb = MTLBlendFactorOneMinusSourceAlpha;
      src_alpha = MTLBlendFactorOne;
      dst_alpha = MTLBlendFactorOneMinusSourceAlpha;
      break;
    }
    case GPU_BLEND_ALPHA_PREMULT: {
      src_rgb = MTLBlendFactorOne;
      dst_rgb = MTLBlendFactorOneMinusSourceAlpha;
      src_alpha = MTLBlendFactorOne;
      dst_alpha = MTLBlendFactorOneMinusSourceAlpha;
      break;
    }
    case GPU_BLEND_ADDITIVE: {
      /* Do not let alpha accumulate but pre-multiply the source RGB by it. */
      src_rgb = MTLBlendFactorSourceAlpha;
      dst_rgb = MTLBlendFactorOne;
      src_alpha = MTLBlendFactorZero;
      dst_alpha = MTLBlendFactorOne;
      break;
    }
    case GPU_BLEND_SUBTRACT:
    case GPU_BLEND_ADDITIVE_PREMULT: {
      /* Let alpha accumulate. */
      src_rgb = MTLBlendFactorOne;
      dst_rgb = MTLBlendFactorOne;
      src_alpha = MTLBlendFactorOne;
      dst_alpha = MTLBlendFactorOne;
      break;
    }
    case GPU_BLEND_MULTIPLY: {
      src_rgb = MTLBlendFactorDestinationColor;
      dst_rgb = MTLBlendFactorZero;
      src_alpha = MTLBlendFactorDestinationAlpha;
      dst_alpha = MTLBlendFactorZero;
      break;
    }
    case GPU_BLEND_INVERT: {
      src_rgb = MTLBlendFactorOneMinusDestinationColor;
      dst_rgb = MTLBlendFactorZero;
      src_alpha = MTLBlendFactorZero;
      dst_alpha = MTLBlendFactorOne;
      break;
    }
    case GPU_BLEND_OIT: {
      src_rgb = MTLBlendFactorOne;
      dst_rgb = MTLBlendFactorOne;
      src_alpha = MTLBlendFactorZero;
      dst_alpha = MTLBlendFactorOneMinusSourceAlpha;
      break;
    }
    case GPU_BLEND_BACKGROUND: {
      src_rgb = MTLBlendFactorOneMinusDestinationAlpha;
      dst_rgb = MTLBlendFactorSourceAlpha;
      src_alpha = MTLBlendFactorZero;
      dst_alpha = MTLBlendFactorSourceAlpha;
      break;
    }
    case GPU_BLEND_ALPHA_UNDER_PREMUL: {
      src_rgb = MTLBlendFactorOneMinusDestinationAlpha;
      dst_rgb = MTLBlendFactorOne;
      src_alpha = MTLBlendFactorOneMinusDestinationAlpha;
      dst_alpha = MTLBlendFactorOne;
      break;
    }
    case GPU_BLEND_CUSTOM: {
      src_rgb = MTLBlendFactorOne;
      dst_rgb = MTLBlendFactorSource1Color;
      src_alpha = MTLBlendFactorOne;
      dst_alpha = MTLBlendFactorSource1Alpha;
      break;
    }
  }

  /* Check Current Context. */
  BLI_assert(context_);
  MTLContextGlobalShaderPipelineState &pipeline_state = context_->pipeline_state;

  if (value == GPU_BLEND_SUBTRACT) {
    pipeline_state.rgb_blend_op = MTLBlendOperationReverseSubtract;
    pipeline_state.alpha_blend_op = MTLBlendOperationReverseSubtract;
  }
  else {
    pipeline_state.rgb_blend_op = MTLBlendOperationAdd;
    pipeline_state.alpha_blend_op = MTLBlendOperationAdd;
  }

  /* Apply State. */
  pipeline_state.blending_enabled = (value != GPU_BLEND_NONE);
  pipeline_state.src_rgb_blend_factor = src_rgb;
  pipeline_state.dest_rgb_blend_factor = dst_rgb;
  pipeline_state.src_alpha_blend_factor = src_alpha;
  pipeline_state.dest_alpha_blend_factor = dst_alpha;

  /* Mark Dirty - Ensure context updates PSOs between draws. */
  pipeline_state.dirty_flags |= MTL_PIPELINE_STATE_PSO_FLAG;
  pipeline_state.dirty = true;
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Memory barrier
 * \{ */

/* NOTE(Metal): Granular option for specifying before/after stages for a barrier
 * Would be a useful feature. */
#if 0
void MTLStateManager::issue_barrier(eGPUBarrier barrier_bits,
                                    eGPUStageBarrierBits before_stages,
                                    eGPUStageBarrierBits after_stages)
#endif
void MTLStateManager::issue_barrier(eGPUBarrier barrier_bits)
{
  /* NOTE(Metal): The Metal API implicitly tracks dependencies between resources.
   * Memory barriers and execution barriers (Fences/Events) can be used to coordinate
   * this explicitly, however, in most cases, the driver will be able to
   * resolve these dependencies automatically.
   * For untracked resources, such as MTLHeap's, explicit barriers are necessary. */
  eGPUStageBarrierBits before_stages = GPU_BARRIER_STAGE_ANY;
  eGPUStageBarrierBits after_stages = GPU_BARRIER_STAGE_ANY;

  MTLContext *ctx = reinterpret_cast<MTLContext *>(GPU_context_active_get());
  BLI_assert(ctx);

  /* Apple Silicon does not support memory barriers.
   * We do not currently need these due to implicit API guarantees.
   * Note(Metal): MTLFence/MTLEvent may be required to synchronize work if
   * untracked resources are ever used. */
  if ([ctx->device hasUnifiedMemory]) {
    return;
  }

  ctx->main_command_buffer.insert_memory_barrier(barrier_bits, before_stages, after_stages);
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Texture State Management
 * \{ */

void MTLStateManager::texture_unpack_row_length_set(uint len)
{
  /* Set source image row data stride when uploading image data to the GPU. */
  MTLContext *ctx = static_cast<MTLContext *>(unwrap(GPU_context_active_get()));
  ctx->pipeline_state.unpack_row_length = len;
}

void MTLStateManager::texture_bind(Texture *tex_, eGPUSamplerState sampler_type, int unit)
{
  BLI_assert(tex_);
  gpu::MTLTexture *mtl_tex = static_cast<gpu::MTLTexture *>(tex_);
  BLI_assert(mtl_tex);

  MTLContext *ctx = static_cast<MTLContext *>(unwrap(GPU_context_active_get()));
  if (unit >= 0) {
    ctx->texture_bind(mtl_tex, unit);

    /* Fetching textures default sampler configuration and applying
     * eGPUSampler State on top. This path exists to support
     * Any of the sampler state which is associated with the
     * texture itself such as min/max mip levels. */
    MTLSamplerState sampler = mtl_tex->get_sampler_state();
    sampler.state = sampler_type;

    ctx->sampler_bind(sampler, unit);
  }
}

void MTLStateManager::texture_unbind(Texture *tex_)
{
  BLI_assert(tex_);
  gpu::MTLTexture *mtl_tex = static_cast<gpu::MTLTexture *>(tex_);
  BLI_assert(mtl_tex);
  MTLContext *ctx = static_cast<MTLContext *>(unwrap(GPU_context_active_get()));
  ctx->texture_unbind(mtl_tex);
}

void MTLStateManager::texture_unbind_all(void)
{
  MTLContext *ctx = static_cast<MTLContext *>(unwrap(GPU_context_active_get()));
  BLI_assert(ctx);
  ctx->texture_unbind_all();
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Image Binding (from image load store)
 * \{ */

void MTLStateManager::image_bind(Texture *tex_, int unit)
{
  this->texture_bind(tex_, GPU_SAMPLER_DEFAULT, unit);
}

void MTLStateManager::image_unbind(Texture *tex_)
{
  this->texture_unbind(tex_);
}

void MTLStateManager::image_unbind_all(void)
{
  this->texture_unbind_all();
}

/** \} */

}  // blender::gpu