src/dawn/native/BlitColorToColorWithDraw.cpp - dawn - 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