src/dawn/native/BlitColorToColorWithDraw.cpp - dawn.git - Git at Google

 // Copyright 2023 The Dawn & Tint Authors
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are met:
 //
 // 1. Redistributions of source code must retain the above copyright notice, this
 //    list of conditions and the following disclaimer.
 //
 // 2. Redistributions in binary form must reproduce the above copyright notice,
 //    this list of conditions and the following disclaimer in the documentation
 //    and/or other materials provided with the distribution.
 //
 // 3. Neither the name of the copyright holder nor the names of its
 //    contributors may be used to endorse or promote products derived from
 //    this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 #include "dawn/native/BlitColorToColorWithDraw.h"

 #include <sstream>
 #include <string>

 #include "absl/container/inlined_vector.h"
 #include "dawn/common/Assert.h"
 #include "dawn/common/Enumerator.h"
 #include "dawn/common/HashUtils.h"
 #include "dawn/native/BindGroup.h"
 #include "dawn/native/ChainUtils.h"
 #include "dawn/native/CommandEncoder.h"
 #include "dawn/native/Device.h"
 #include "dawn/native/InternalPipelineStore.h"
 #include "dawn/native/RenderPassEncoder.h"
 #include "dawn/native/RenderPipeline.h"
 #include "dawn/native/utils/WGPUHelpers.h"
 #include "dawn/native/webgpu_absl_format.h"

 namespace dawn::native {

 namespace {

 constexpr char kBlitToColorVS[] = R"(

 @vertex fn vert_fullscreen_quad(
   @builtin(vertex_index) vertex_index : u32,
 ) -> @builtin(position) vec4f {
   const pos = array(
       vec2f(-1.0, -1.0),
       vec2f( 3.0, -1.0),
       vec2f(-1.0,  3.0));
   return vec4f(pos[vertex_index], 0.0, 1.0);
 }
 )";

 std::string GenerateExpandFS(const BlitColorToColorWithDrawPipelineKey& pipelineKey) {
     std::ostringstream outputStructStream;
     std::ostringstream assignOutputsStream;
     std::ostringstream finalStream;

     for (auto i : IterateBitSet(pipelineKey.attachmentsToExpandResolve)) {
         finalStream << absl::StrFormat("@group(0) @binding(%u) var srcTex%u : texture_2d<f32>;\n",
                                        i, i);

         outputStructStream << absl::StrFormat("@location(%u) output%u : vec4f,\n", i, i);

         assignOutputsStream << absl::StrFormat(
             "\toutputColor.output%u = textureLoad(srcTex%u, vec2u(position.xy), 0);\n", i, i);
     }

     finalStream << "struct OutputColor {\n" << outputStructStream.str() << "}\n\n";
     finalStream << R"(
 @fragment fn expand_multisample(@builtin(position) position : vec4f) -> OutputColor {
     var outputColor : OutputColor;
 )" << assignOutputsStream.str()
                 << R"(
     return outputColor;
 })";

     return finalStream.str();
 }

 // Generate the fragment shader to average multiple samples into one.
 std::string GenerateResolveFS(uint32_t sampleCount) {
     std::ostringstream ss;

     ss << R"(
 @group(0) @binding(0) var srcTex : texture_multisampled_2d<f32>;

 @fragment
 fn resolve_multisample(@builtin(position) position : vec4f) -> @location(0) vec4f {
     var sum = vec4f(0.0, 0.0, 0.0, 0.0);)";
     ss << "\n";
     for (uint32_t sample = 0; sample < sampleCount; ++sample) {
         ss << absl::StrFormat("    sum += textureLoad(srcTex, vec2u(position.xy), %u);\n", sample);
     }
     ss << absl::StrFormat("    return sum / %u;\n", sampleCount) << "}\n";

     return ss.str();
 }

 ResultOrError<Ref<RenderPipelineBase>> GetOrCreateExpandMultisamplePipeline(
     DeviceBase* device,
     const BlitColorToColorWithDrawPipelineKey& pipelineKey,
     uint8_t colorAttachmentCount) {
     InternalPipelineStore* store = device->GetInternalPipelineStore();
     {
         auto it = store->expandResolveTexturePipelines.find(pipelineKey);
         if (it != store->expandResolveTexturePipelines.end()) {
             return it->second;
         }
     }

     // vertex shader's source.
     ShaderSourceWGSL wgslDesc = {};
     ShaderModuleDescriptor shaderModuleDesc = {};
     shaderModuleDesc.nextInChain = &wgslDesc;
     wgslDesc.code = kBlitToColorVS;

     Ref<ShaderModuleBase> vshaderModule;
     DAWN_TRY_ASSIGN(vshaderModule, device->CreateShaderModule(&shaderModuleDesc));

     // fragment shader's source will depend on pipeline key.
     std::string fsCode = GenerateExpandFS(pipelineKey);
     wgslDesc.code = fsCode.c_str();
     Ref<ShaderModuleBase> fshaderModule;
     DAWN_TRY_ASSIGN(fshaderModule, device->CreateShaderModule(&shaderModuleDesc));

     FragmentState fragmentState = {};
     fragmentState.module = fshaderModule.Get();
     fragmentState.entryPoint = "expand_multisample";

     // Color target states.
     PerColorAttachment<ColorTargetState> colorTargets = {};
     PerColorAttachment<wgpu::ColorTargetStateExpandResolveTextureDawn> msaaExpandResolveStates;

     for (auto [i, target] : Enumerate(colorTargets)) {
         target.format = pipelineKey.colorTargetFormats[i];
         // We shouldn't change the color targets that are not involved in.
         if (pipelineKey.resolveTargetsMask[i]) {
             target.nextInChain = &msaaExpandResolveStates[i];
             msaaExpandResolveStates[i].enabled = pipelineKey.attachmentsToExpandResolve[i];
             if (msaaExpandResolveStates[i].enabled) {
                 target.writeMask = wgpu::ColorWriteMask::All;
             } else {
                 target.writeMask = wgpu::ColorWriteMask::None;
             }
         } else {
             target.writeMask = wgpu::ColorWriteMask::None;
         }
     }

     fragmentState.targetCount = colorAttachmentCount;
     fragmentState.targets = colorTargets.data();

     RenderPipelineDescriptor renderPipelineDesc = {};
     renderPipelineDesc.label = "expand_multisample";
     renderPipelineDesc.vertex.module = vshaderModule.Get();
     renderPipelineDesc.vertex.entryPoint = "vert_fullscreen_quad";
     renderPipelineDesc.fragment = &fragmentState;

     // Depth stencil state.
     DepthStencilState depthStencilState = {};
     if (pipelineKey.depthStencilFormat != wgpu::TextureFormat::Undefined) {
         depthStencilState.format = pipelineKey.depthStencilFormat;
         depthStencilState.depthWriteEnabled = wgpu::OptionalBool::False;
         depthStencilState.depthCompare = wgpu::CompareFunction::Always;

         renderPipelineDesc.depthStencil = &depthStencilState;
     }

     // Multisample state.
     DAWN_ASSERT(pipelineKey.sampleCount > 1);
     renderPipelineDesc.multisample.count = pipelineKey.sampleCount;

     // Bind group layout.
     absl::InlinedVector<BindGroupLayoutEntry, kMaxColorAttachments> bglEntries;
     for (auto colorIdx : IterateBitSet(pipelineKey.attachmentsToExpandResolve)) {
         bglEntries.push_back({});
         auto& bglEntry = bglEntries.back();
         bglEntry.binding = static_cast<uint8_t>(colorIdx);
         bglEntry.visibility = wgpu::ShaderStage::Fragment;
         bglEntry.texture.sampleType = kInternalResolveAttachmentSampleType;
         bglEntry.texture.viewDimension = wgpu::TextureViewDimension::e2D;
     }
     BindGroupLayoutDescriptor bglDesc = {};
     bglDesc.entries = bglEntries.data();
     bglDesc.entryCount = bglEntries.size();

     Ref<BindGroupLayoutBase> bindGroupLayout;
     DAWN_TRY_ASSIGN(bindGroupLayout,
                     device->CreateBindGroupLayout(&bglDesc, /* allowInternalBinding */ true));

     Ref<PipelineLayoutBase> pipelineLayout;
     DAWN_TRY_ASSIGN(pipelineLayout, utils::MakeBasicPipelineLayout(device, bindGroupLayout));
     renderPipelineDesc.layout = pipelineLayout.Get();

     Ref<RenderPipelineBase> pipeline;
     DAWN_TRY_ASSIGN(pipeline, device->CreateRenderPipeline(&renderPipelineDesc));

     store->expandResolveTexturePipelines.emplace(pipelineKey, pipeline);
     return pipeline;
 }

 ResultOrError<Ref<RenderPipelineBase>> GetOrCreateResolveMultisamplePipeline(
     DeviceBase* device,
     const ResolveMultisampleWithDrawPipelineKey& pipelineKey) {
     // Try finding the pipeline from the cache.
     InternalPipelineStore* store = device->GetInternalPipelineStore();
     {
         auto it = store->resolveMultisamplePipelines.find(pipelineKey);
         if (it != store->resolveMultisamplePipelines.end()) {
             return it->second;
         }
     }

     // vertex shader's source.
     ShaderSourceWGSL wgslDesc = {};
     ShaderModuleDescriptor shaderModuleDesc = {};
     shaderModuleDesc.nextInChain = &wgslDesc;
     wgslDesc.code = kBlitToColorVS;

     Ref<ShaderModuleBase> vshaderModule;
     DAWN_TRY_ASSIGN(vshaderModule, device->CreateShaderModule(&shaderModuleDesc));

     // fragment shader's source will depend on sample count.
     std::string fsCode = GenerateResolveFS(pipelineKey.sampleCount);
     wgslDesc.code = fsCode.c_str();
     Ref<ShaderModuleBase> fshaderModule;
     DAWN_TRY_ASSIGN(fshaderModule, device->CreateShaderModule(&shaderModuleDesc));

     FragmentState fragmentState = {};
     fragmentState.module = fshaderModule.Get();
     fragmentState.entryPoint = "resolve_multisample";

     // Color target states.
     ColorTargetState colorTarget = {};
     colorTarget.format = pipelineKey.colorTargetFormat;

     fragmentState.targetCount = 1;
     fragmentState.targets = &colorTarget;

     RenderPipelineDescriptor renderPipelineDesc = {};
     renderPipelineDesc.label = "resolve_multisample";
     renderPipelineDesc.vertex.module = vshaderModule.Get();
     renderPipelineDesc.vertex.entryPoint = "vert_fullscreen_quad";
     renderPipelineDesc.fragment = &fragmentState;

     Ref<RenderPipelineBase> pipeline;
     DAWN_TRY_ASSIGN(pipeline, device->CreateRenderPipeline(&renderPipelineDesc));

     store->resolveMultisamplePipelines.emplace(pipelineKey, pipeline);
     return pipeline;
 }

 }  // namespace

 MaybeError ExpandResolveTextureWithDraw(
     DeviceBase* device,
     RenderPassEncoder* renderEncoder,
     const UnpackedPtr<RenderPassDescriptor>& renderPassDescriptor) {
     DAWN_ASSERT(device->IsLockedByCurrentThreadIfNeeded());
     DAWN_ASSERT(device->CanTextureLoadResolveTargetInTheSameRenderpass());

     BlitColorToColorWithDrawPipelineKey pipelineKey;
     for (uint8_t i = 0; i < renderPassDescriptor->colorAttachmentCount; ++i) {
         ColorAttachmentIndex colorIdx(i);
         const auto& colorAttachment = renderPassDescriptor->colorAttachments[i];
         TextureViewBase* view = colorAttachment.view;
         if (!view) {
             continue;
         }
         const Format& format = view->GetFormat();
         TextureComponentType baseType = format.GetAspectInfo(Aspect::Color).baseType;
         // TODO(dawn:1710): blitting integer textures are not currently supported.
         DAWN_ASSERT(baseType == TextureComponentType::Float);

         if (colorAttachment.loadOp == wgpu::LoadOp::ExpandResolveTexture) {
             DAWN_ASSERT(colorAttachment.resolveTarget->GetLayerCount() == 1u);
             DAWN_ASSERT(colorAttachment.resolveTarget->GetDimension() ==
                         wgpu::TextureViewDimension::e2D);
             pipelineKey.attachmentsToExpandResolve.set(colorIdx);
         }
         pipelineKey.resolveTargetsMask.set(colorIdx, colorAttachment.resolveTarget);

         pipelineKey.colorTargetFormats[colorIdx] = format.format;
         pipelineKey.sampleCount = view->GetTexture()->GetSampleCount();
     }

     if (!pipelineKey.attachmentsToExpandResolve.any()) {
         return {};
     }

     pipelineKey.depthStencilFormat = wgpu::TextureFormat::Undefined;
     if (renderPassDescriptor->depthStencilAttachment != nullptr) {
         pipelineKey.depthStencilFormat =
             renderPassDescriptor->depthStencilAttachment->view->GetFormat().format;
     }

     Ref<RenderPipelineBase> pipeline;
     DAWN_TRY_ASSIGN(pipeline, GetOrCreateExpandMultisamplePipeline(
                                   device, pipelineKey, renderPassDescriptor->colorAttachmentCount));

     Ref<BindGroupLayoutBase> bgl;
     DAWN_TRY_ASSIGN(bgl, pipeline->GetBindGroupLayout(0));

     Ref<BindGroupBase> bindGroup;
     {
         absl::InlinedVector<BindGroupEntry, kMaxColorAttachments> bgEntries = {};

         for (auto colorIdx : IterateBitSet(pipelineKey.attachmentsToExpandResolve)) {
             uint8_t i = static_cast<uint8_t>(colorIdx);
             const auto& colorAttachment = renderPassDescriptor->colorAttachments[i];
             bgEntries.push_back({});
             auto& bgEntry = bgEntries.back();
             bgEntry.binding = i;
             bgEntry.textureView = colorAttachment.resolveTarget;
         }

         BindGroupDescriptor bgDesc = {};
         bgDesc.layout = bgl.Get();
         bgDesc.entryCount = bgEntries.size();
         bgDesc.entries = bgEntries.data();
         DAWN_TRY_ASSIGN(bindGroup, device->CreateBindGroup(&bgDesc, UsageValidationMode::Internal));
     }

     // Draw to perform the blit.
     renderEncoder->APISetBindGroup(0, bindGroup.Get());
     renderEncoder->APISetPipeline(pipeline.Get());

     if (const auto* rect = renderPassDescriptor.Get<RenderPassDescriptorExpandResolveRect>()) {
         // TODO(chromium:344814092): Prevent the scissor to be reset to outside of this region by
         // passing the scissor bound to the render pass creation.
         renderEncoder->APISetScissorRect(rect->x, rect->y, rect->width, rect->height);
     }

     renderEncoder->APIDraw(3);

     return {};
 }

 size_t BlitColorToColorWithDrawPipelineKey::HashFunc::operator()(
     const BlitColorToColorWithDrawPipelineKey& key) const {
     size_t hash = 0;

     HashCombine(&hash, key.attachmentsToExpandResolve);
     HashCombine(&hash, key.resolveTargetsMask);

     for (auto format : key.colorTargetFormats) {
         HashCombine(&hash, format);
     }

     HashCombine(&hash, key.depthStencilFormat);
     HashCombine(&hash, key.sampleCount);

     return hash;
 }

 bool BlitColorToColorWithDrawPipelineKey::EqualityFunc::operator()(
     const BlitColorToColorWithDrawPipelineKey& a,
     const BlitColorToColorWithDrawPipelineKey& b) const {
     if (a.attachmentsToExpandResolve != b.attachmentsToExpandResolve) {
         return false;
     }
     if (a.resolveTargetsMask != b.resolveTargetsMask) {
         return false;
     }

     for (auto [i, format] : Enumerate(a.colorTargetFormats)) {
         if (format != b.colorTargetFormats[i]) {
             return false;
         }
     }

     return a.depthStencilFormat == b.depthStencilFormat && a.sampleCount == b.sampleCount;
 }

 MaybeError ResolveMultisampleWithDraw(DeviceBase* device,
                                       CommandEncoder* encoder,
                                       Rect2D rect,
                                       TextureViewBase* src,
                                       TextureViewBase* dst) {
     DAWN_ASSERT(device->IsLockedByCurrentThreadIfNeeded());

     ResolveMultisampleWithDrawPipelineKey pipelineKey{dst->GetFormat().format,
                                                       src->GetTexture()->GetSampleCount()};
     Ref<RenderPipelineBase> pipeline;
     DAWN_TRY_ASSIGN(pipeline, GetOrCreateResolveMultisamplePipeline(device, pipelineKey));

     Ref<BindGroupLayoutBase> bindGroupLayout;
     DAWN_TRY_ASSIGN(bindGroupLayout, pipeline->GetBindGroupLayout(0));

     Ref<BindGroupBase> bindGroup;
     DAWN_TRY_ASSIGN(bindGroup, utils::MakeBindGroup(device, bindGroupLayout, {{0, src}},
                                                     UsageValidationMode::Internal));

     // Color attachment descriptor.
     RenderPassColorAttachment colorAttachmentDesc;
     colorAttachmentDesc.view = dst;
     colorAttachmentDesc.loadOp = wgpu::LoadOp::Load;
     colorAttachmentDesc.storeOp = wgpu::StoreOp::Store;

     // Create render pass.
     RenderPassDescriptor renderPassDesc;
     renderPassDesc.colorAttachmentCount = 1;
     renderPassDesc.colorAttachments = &colorAttachmentDesc;
     Ref<RenderPassEncoder> renderEncoder = encoder->BeginRenderPass(&renderPassDesc);

     // Draw to perform the resolve.
     renderEncoder->APISetBindGroup(0, bindGroup.Get(), 0, nullptr);
     renderEncoder->APISetPipeline(pipeline.Get());
     renderEncoder->APISetScissorRect(rect.x, rect.y, rect.width, rect.height);
     renderEncoder->APIDraw(3);
     renderEncoder->End();

     return {};
 }

 size_t ResolveMultisampleWithDrawPipelineKey::HashFunc::operator()(
     const ResolveMultisampleWithDrawPipelineKey& key) const {
     size_t hash = 0;

     HashCombine(&hash, key.colorTargetFormat);
     HashCombine(&hash, key.sampleCount);

     return hash;
 }

 bool ResolveMultisampleWithDrawPipelineKey::EqualityFunc::operator()(
     const ResolveMultisampleWithDrawPipelineKey& a,
     const ResolveMultisampleWithDrawPipelineKey& b) const {
     return a.colorTargetFormat == b.colorTargetFormat && a.sampleCount == b.sampleCount;
 }

 }  // namespace dawn::native
	// Copyright 2023 The Dawn & Tint Authors
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are met:
	//
	// 1. Redistributions of source code must retain the above copyright notice, this
	// list of conditions and the following disclaimer.
	//
	// 2. Redistributions in binary form must reproduce the above copyright notice,
	// this list of conditions and the following disclaimer in the documentation
	// and/or other materials provided with the distribution.
	//
	// 3. Neither the name of the copyright holder nor the names of its
	// contributors may be used to endorse or promote products derived from
	// this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
	// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
	// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	#include "dawn/native/BlitColorToColorWithDraw.h"

	#include <sstream>
	#include <string>

	#include "absl/container/inlined_vector.h"
	#include "dawn/common/Assert.h"
	#include "dawn/common/Enumerator.h"
	#include "dawn/common/HashUtils.h"
	#include "dawn/native/BindGroup.h"
	#include "dawn/native/ChainUtils.h"
	#include "dawn/native/CommandEncoder.h"
	#include "dawn/native/Device.h"
	#include "dawn/native/InternalPipelineStore.h"
	#include "dawn/native/RenderPassEncoder.h"
	#include "dawn/native/RenderPipeline.h"
	#include "dawn/native/utils/WGPUHelpers.h"
	#include "dawn/native/webgpu_absl_format.h"

	namespace dawn::native {

	namespace {

	constexpr char kBlitToColorVS[] = R"(

	@vertex fn vert_fullscreen_quad(
	@builtin(vertex_index) vertex_index : u32,
	) -> @builtin(position) vec4f {
	const pos = array(
	vec2f(-1.0, -1.0),
	vec2f( 3.0, -1.0),
	vec2f(-1.0, 3.0));
	return vec4f(pos[vertex_index], 0.0, 1.0);
	}
	)";

	std::string GenerateExpandFS(const BlitColorToColorWithDrawPipelineKey& pipelineKey) {
	std::ostringstream outputStructStream;
	std::ostringstream assignOutputsStream;
	std::ostringstream finalStream;

	for (auto i : IterateBitSet(pipelineKey.attachmentsToExpandResolve)) {
	finalStream << absl::StrFormat("@group(0) @binding(%u) var srcTex%u : texture_2d<f32>;\n",
	i, i);

	outputStructStream << absl::StrFormat("@location(%u) output%u : vec4f,\n", i, i);

	assignOutputsStream << absl::StrFormat(
	"\toutputColor.output%u = textureLoad(srcTex%u, vec2u(position.xy), 0);\n", i, i);
	}

	finalStream << "struct OutputColor {\n" << outputStructStream.str() << "}\n\n";
	finalStream << R"(
	@fragment fn expand_multisample(@builtin(position) position : vec4f) -> OutputColor {
	var outputColor : OutputColor;
	)" << assignOutputsStream.str()
	<< R"(
	return outputColor;
	})";

	return finalStream.str();
	}

	// Generate the fragment shader to average multiple samples into one.
	std::string GenerateResolveFS(uint32_t sampleCount) {
	std::ostringstream ss;

	ss << R"(
	@group(0) @binding(0) var srcTex : texture_multisampled_2d<f32>;

	@fragment
	fn resolve_multisample(@builtin(position) position : vec4f) -> @location(0) vec4f {
	var sum = vec4f(0.0, 0.0, 0.0, 0.0);)";
	ss << "\n";
	for (uint32_t sample = 0; sample < sampleCount; ++sample) {
	ss << absl::StrFormat(" sum += textureLoad(srcTex, vec2u(position.xy), %u);\n", sample);
	}
	ss << absl::StrFormat(" return sum / %u;\n", sampleCount) << "}\n";

	return ss.str();
	}

	ResultOrError<Ref<RenderPipelineBase>> GetOrCreateExpandMultisamplePipeline(
	DeviceBase* device,
	const BlitColorToColorWithDrawPipelineKey& pipelineKey,
	uint8_t colorAttachmentCount) {
	InternalPipelineStore* store = device->GetInternalPipelineStore();
	{
	auto it = store->expandResolveTexturePipelines.find(pipelineKey);
	if (it != store->expandResolveTexturePipelines.end()) {
	return it->second;
	}
	}

	// vertex shader's source.
	ShaderSourceWGSL wgslDesc = {};
	ShaderModuleDescriptor shaderModuleDesc = {};
	shaderModuleDesc.nextInChain = &wgslDesc;
	wgslDesc.code = kBlitToColorVS;

	Ref<ShaderModuleBase> vshaderModule;
	DAWN_TRY_ASSIGN(vshaderModule, device->CreateShaderModule(&shaderModuleDesc));

	// fragment shader's source will depend on pipeline key.
	std::string fsCode = GenerateExpandFS(pipelineKey);
	wgslDesc.code = fsCode.c_str();
	Ref<ShaderModuleBase> fshaderModule;
	DAWN_TRY_ASSIGN(fshaderModule, device->CreateShaderModule(&shaderModuleDesc));

	FragmentState fragmentState = {};
	fragmentState.module = fshaderModule.Get();
	fragmentState.entryPoint = "expand_multisample";

	// Color target states.
	PerColorAttachment<ColorTargetState> colorTargets = {};
	PerColorAttachment<wgpu::ColorTargetStateExpandResolveTextureDawn> msaaExpandResolveStates;

	for (auto [i, target] : Enumerate(colorTargets)) {
	target.format = pipelineKey.colorTargetFormats[i];
	// We shouldn't change the color targets that are not involved in.
	if (pipelineKey.resolveTargetsMask[i]) {
	target.nextInChain = &msaaExpandResolveStates[i];
	msaaExpandResolveStates[i].enabled = pipelineKey.attachmentsToExpandResolve[i];
	if (msaaExpandResolveStates[i].enabled) {
	target.writeMask = wgpu::ColorWriteMask::All;
	} else {
	target.writeMask = wgpu::ColorWriteMask::None;
	}
	} else {
	target.writeMask = wgpu::ColorWriteMask::None;
	}
	}

	fragmentState.targetCount = colorAttachmentCount;
	fragmentState.targets = colorTargets.data();

	RenderPipelineDescriptor renderPipelineDesc = {};
	renderPipelineDesc.label = "expand_multisample";
	renderPipelineDesc.vertex.module = vshaderModule.Get();
	renderPipelineDesc.vertex.entryPoint = "vert_fullscreen_quad";
	renderPipelineDesc.fragment = &fragmentState;

	// Depth stencil state.
	DepthStencilState depthStencilState = {};
	if (pipelineKey.depthStencilFormat != wgpu::TextureFormat::Undefined) {
	depthStencilState.format = pipelineKey.depthStencilFormat;
	depthStencilState.depthWriteEnabled = wgpu::OptionalBool::False;
	depthStencilState.depthCompare = wgpu::CompareFunction::Always;

	renderPipelineDesc.depthStencil = &depthStencilState;
	}

	// Multisample state.
	DAWN_ASSERT(pipelineKey.sampleCount > 1);
	renderPipelineDesc.multisample.count = pipelineKey.sampleCount;

	// Bind group layout.
	absl::InlinedVector<BindGroupLayoutEntry, kMaxColorAttachments> bglEntries;
	for (auto colorIdx : IterateBitSet(pipelineKey.attachmentsToExpandResolve)) {
	bglEntries.push_back({});
	auto& bglEntry = bglEntries.back();
	bglEntry.binding = static_cast<uint8_t>(colorIdx);
	bglEntry.visibility = wgpu::ShaderStage::Fragment;
	bglEntry.texture.sampleType = kInternalResolveAttachmentSampleType;
	bglEntry.texture.viewDimension = wgpu::TextureViewDimension::e2D;
	}
	BindGroupLayoutDescriptor bglDesc = {};
	bglDesc.entries = bglEntries.data();
	bglDesc.entryCount = bglEntries.size();

	Ref<BindGroupLayoutBase> bindGroupLayout;
	DAWN_TRY_ASSIGN(bindGroupLayout,
	device->CreateBindGroupLayout(&bglDesc, /* allowInternalBinding */ true));

	Ref<PipelineLayoutBase> pipelineLayout;
	DAWN_TRY_ASSIGN(pipelineLayout, utils::MakeBasicPipelineLayout(device, bindGroupLayout));
	renderPipelineDesc.layout = pipelineLayout.Get();

	Ref<RenderPipelineBase> pipeline;
	DAWN_TRY_ASSIGN(pipeline, device->CreateRenderPipeline(&renderPipelineDesc));

	store->expandResolveTexturePipelines.emplace(pipelineKey, pipeline);
	return pipeline;
	}

	ResultOrError<Ref<RenderPipelineBase>> GetOrCreateResolveMultisamplePipeline(
	DeviceBase* device,
	const ResolveMultisampleWithDrawPipelineKey& pipelineKey) {
	// Try finding the pipeline from the cache.
	InternalPipelineStore* store = device->GetInternalPipelineStore();
	{
	auto it = store->resolveMultisamplePipelines.find(pipelineKey);
	if (it != store->resolveMultisamplePipelines.end()) {
	return it->second;
	}
	}

	// vertex shader's source.
	ShaderSourceWGSL wgslDesc = {};
	ShaderModuleDescriptor shaderModuleDesc = {};
	shaderModuleDesc.nextInChain = &wgslDesc;
	wgslDesc.code = kBlitToColorVS;

	Ref<ShaderModuleBase> vshaderModule;
	DAWN_TRY_ASSIGN(vshaderModule, device->CreateShaderModule(&shaderModuleDesc));

	// fragment shader's source will depend on sample count.
	std::string fsCode = GenerateResolveFS(pipelineKey.sampleCount);
	wgslDesc.code = fsCode.c_str();
	Ref<ShaderModuleBase> fshaderModule;
	DAWN_TRY_ASSIGN(fshaderModule, device->CreateShaderModule(&shaderModuleDesc));

	FragmentState fragmentState = {};
	fragmentState.module = fshaderModule.Get();
	fragmentState.entryPoint = "resolve_multisample";

	// Color target states.
	ColorTargetState colorTarget = {};
	colorTarget.format = pipelineKey.colorTargetFormat;

	fragmentState.targetCount = 1;
	fragmentState.targets = &colorTarget;

	RenderPipelineDescriptor renderPipelineDesc = {};
	renderPipelineDesc.label = "resolve_multisample";
	renderPipelineDesc.vertex.module = vshaderModule.Get();
	renderPipelineDesc.vertex.entryPoint = "vert_fullscreen_quad";
	renderPipelineDesc.fragment = &fragmentState;

	Ref<RenderPipelineBase> pipeline;
	DAWN_TRY_ASSIGN(pipeline, device->CreateRenderPipeline(&renderPipelineDesc));

	store->resolveMultisamplePipelines.emplace(pipelineKey, pipeline);
	return pipeline;
	}

	} // namespace

	MaybeError ExpandResolveTextureWithDraw(
	DeviceBase* device,
	RenderPassEncoder* renderEncoder,
	const UnpackedPtr<RenderPassDescriptor>& renderPassDescriptor) {
	DAWN_ASSERT(device->IsLockedByCurrentThreadIfNeeded());
	DAWN_ASSERT(device->CanTextureLoadResolveTargetInTheSameRenderpass());

	BlitColorToColorWithDrawPipelineKey pipelineKey;
	for (uint8_t i = 0; i < renderPassDescriptor->colorAttachmentCount; ++i) {
	ColorAttachmentIndex colorIdx(i);
	const auto& colorAttachment = renderPassDescriptor->colorAttachments[i];
	TextureViewBase* view = colorAttachment.view;
	if (!view) {
	continue;
	}
	const Format& format = view->GetFormat();
	TextureComponentType baseType = format.GetAspectInfo(Aspect::Color).baseType;
	// TODO(dawn:1710): blitting integer textures are not currently supported.
	DAWN_ASSERT(baseType == TextureComponentType::Float);

	if (colorAttachment.loadOp == wgpu::LoadOp::ExpandResolveTexture) {
	DAWN_ASSERT(colorAttachment.resolveTarget->GetLayerCount() == 1u);
	DAWN_ASSERT(colorAttachment.resolveTarget->GetDimension() ==
	wgpu::TextureViewDimension::e2D);
	pipelineKey.attachmentsToExpandResolve.set(colorIdx);
	}
	pipelineKey.resolveTargetsMask.set(colorIdx, colorAttachment.resolveTarget);

	pipelineKey.colorTargetFormats[colorIdx] = format.format;
	pipelineKey.sampleCount = view->GetTexture()->GetSampleCount();
	}

	if (!pipelineKey.attachmentsToExpandResolve.any()) {
	return {};
	}

	pipelineKey.depthStencilFormat = wgpu::TextureFormat::Undefined;
	if (renderPassDescriptor->depthStencilAttachment != nullptr) {
	pipelineKey.depthStencilFormat =
	renderPassDescriptor->depthStencilAttachment->view->GetFormat().format;
	}

	Ref<RenderPipelineBase> pipeline;
	DAWN_TRY_ASSIGN(pipeline, GetOrCreateExpandMultisamplePipeline(
	device, pipelineKey, renderPassDescriptor->colorAttachmentCount));

	Ref<BindGroupLayoutBase> bgl;
	DAWN_TRY_ASSIGN(bgl, pipeline->GetBindGroupLayout(0));

	Ref<BindGroupBase> bindGroup;
	{
	absl::InlinedVector<BindGroupEntry, kMaxColorAttachments> bgEntries = {};

	for (auto colorIdx : IterateBitSet(pipelineKey.attachmentsToExpandResolve)) {
	uint8_t i = static_cast<uint8_t>(colorIdx);
	const auto& colorAttachment = renderPassDescriptor->colorAttachments[i];
	bgEntries.push_back({});
	auto& bgEntry = bgEntries.back();
	bgEntry.binding = i;
	bgEntry.textureView = colorAttachment.resolveTarget;
	}

	BindGroupDescriptor bgDesc = {};
	bgDesc.layout = bgl.Get();
	bgDesc.entryCount = bgEntries.size();
	bgDesc.entries = bgEntries.data();
	DAWN_TRY_ASSIGN(bindGroup, device->CreateBindGroup(&bgDesc, UsageValidationMode::Internal));
	}

	// Draw to perform the blit.
	renderEncoder->APISetBindGroup(0, bindGroup.Get());
	renderEncoder->APISetPipeline(pipeline.Get());

	if (const auto* rect = renderPassDescriptor.Get<RenderPassDescriptorExpandResolveRect>()) {
	// TODO(chromium:344814092): Prevent the scissor to be reset to outside of this region by
	// passing the scissor bound to the render pass creation.
	renderEncoder->APISetScissorRect(rect->x, rect->y, rect->width, rect->height);
	}

	renderEncoder->APIDraw(3);

	return {};
	}

	size_t BlitColorToColorWithDrawPipelineKey::HashFunc::operator()(
	const BlitColorToColorWithDrawPipelineKey& key) const {
	size_t hash = 0;

	HashCombine(&hash, key.attachmentsToExpandResolve);
	HashCombine(&hash, key.resolveTargetsMask);

	for (auto format : key.colorTargetFormats) {
	HashCombine(&hash, format);
	}

	HashCombine(&hash, key.depthStencilFormat);
	HashCombine(&hash, key.sampleCount);

	return hash;
	}

	bool BlitColorToColorWithDrawPipelineKey::EqualityFunc::operator()(
	const BlitColorToColorWithDrawPipelineKey& a,
	const BlitColorToColorWithDrawPipelineKey& b) const {
	if (a.attachmentsToExpandResolve != b.attachmentsToExpandResolve) {
	return false;
	}
	if (a.resolveTargetsMask != b.resolveTargetsMask) {
	return false;
	}

	for (auto [i, format] : Enumerate(a.colorTargetFormats)) {
	if (format != b.colorTargetFormats[i]) {
	return false;
	}
	}

	return a.depthStencilFormat == b.depthStencilFormat && a.sampleCount == b.sampleCount;
	}

	MaybeError ResolveMultisampleWithDraw(DeviceBase* device,
	CommandEncoder* encoder,
	Rect2D rect,
	TextureViewBase* src,
	TextureViewBase* dst) {
	DAWN_ASSERT(device->IsLockedByCurrentThreadIfNeeded());

	ResolveMultisampleWithDrawPipelineKey pipelineKey{dst->GetFormat().format,
	src->GetTexture()->GetSampleCount()};
	Ref<RenderPipelineBase> pipeline;
	DAWN_TRY_ASSIGN(pipeline, GetOrCreateResolveMultisamplePipeline(device, pipelineKey));

	Ref<BindGroupLayoutBase> bindGroupLayout;
	DAWN_TRY_ASSIGN(bindGroupLayout, pipeline->GetBindGroupLayout(0));

	Ref<BindGroupBase> bindGroup;
	DAWN_TRY_ASSIGN(bindGroup, utils::MakeBindGroup(device, bindGroupLayout, {{0, src}},
	UsageValidationMode::Internal));

	// Color attachment descriptor.
	RenderPassColorAttachment colorAttachmentDesc;
	colorAttachmentDesc.view = dst;
	colorAttachmentDesc.loadOp = wgpu::LoadOp::Load;
	colorAttachmentDesc.storeOp = wgpu::StoreOp::Store;

	// Create render pass.
	RenderPassDescriptor renderPassDesc;
	renderPassDesc.colorAttachmentCount = 1;
	renderPassDesc.colorAttachments = &colorAttachmentDesc;
	Ref<RenderPassEncoder> renderEncoder = encoder->BeginRenderPass(&renderPassDesc);

	// Draw to perform the resolve.
	renderEncoder->APISetBindGroup(0, bindGroup.Get(), 0, nullptr);
	renderEncoder->APISetPipeline(pipeline.Get());
	renderEncoder->APISetScissorRect(rect.x, rect.y, rect.width, rect.height);
	renderEncoder->APIDraw(3);
	renderEncoder->End();

	return {};
	}

	size_t ResolveMultisampleWithDrawPipelineKey::HashFunc::operator()(
	const ResolveMultisampleWithDrawPipelineKey& key) const {
	size_t hash = 0;

	HashCombine(&hash, key.colorTargetFormat);
	HashCombine(&hash, key.sampleCount);

	return hash;
	}

	bool ResolveMultisampleWithDrawPipelineKey::EqualityFunc::operator()(
	const ResolveMultisampleWithDrawPipelineKey& a,
	const ResolveMultisampleWithDrawPipelineKey& b) const {
	return a.colorTargetFormat == b.colorTargetFormat && a.sampleCount == b.sampleCount;
	}

	} // namespace dawn::native