src/dawn_native/metal/ShaderModuleMTL.mm

// Copyright 2017 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "dawn_native/metal/ShaderModuleMTL.h"

#include "dawn_native/BindGroupLayout.h"
#include "dawn_native/SpirvUtils.h"
#include "dawn_native/metal/DeviceMTL.h"
#include "dawn_native/metal/PipelineLayoutMTL.h"
#include "dawn_native/metal/RenderPipelineMTL.h"

#include <spirv_msl.hpp>

#include <sstream>

namespace dawn_native { namespace metal {

    // static
    ResultOrError<ShaderModule*> ShaderModule::Create(Device* device,
                                                      const ShaderModuleDescriptor* descriptor) {
        Ref<ShaderModule> module = AcquireRef(new ShaderModule(device, descriptor));
        DAWN_TRY(module->Initialize());
        return module.Detach();
    }

    ShaderModule::ShaderModule(Device* device, const ShaderModuleDescriptor* descriptor)
        : ShaderModuleBase(device, descriptor) {
    }

    MaybeError ShaderModule::Initialize() {
        return InitializeBase();
    }

    MaybeError ShaderModule::CreateFunction(const char* entryPointName,
                                            SingleShaderStage stage,
                                            const PipelineLayout* layout,
                                            ShaderModule::MetalFunctionData* out,
                                            uint32_t sampleMask,
                                            const RenderPipeline* renderPipeline) {
        ASSERT(!IsError());
        ASSERT(out);
        const std::vector<uint32_t>* spirv = &GetSpirv();
        spv::ExecutionModel executionModel = ShaderStageToExecutionModel(stage);

#ifdef DAWN_ENABLE_WGSL
        // Use set 4 since it is bigger than what users can access currently
        static const uint32_t kPullingBufferBindingSet = 4;
        std::vector<uint32_t> pullingSpirv;
        if (GetDevice()->IsToggleEnabled(Toggle::MetalEnableVertexPulling) &&
            stage == SingleShaderStage::Vertex) {
            DAWN_TRY_ASSIGN(pullingSpirv,
                            GeneratePullingSpirv(*renderPipeline->GetVertexStateDescriptor(),
                                                 entryPointName, kPullingBufferBindingSet));
            spirv = &pullingSpirv;
        }
#endif

        // If these options are changed, the values in DawnSPIRVCrossMSLFastFuzzer.cpp need to
        // be updated.
        spirv_cross::CompilerMSL::Options options_msl;

        // Disable PointSize builtin for https://bugs.chromium.org/p/dawn/issues/detail?id=146
        // Because Metal will reject PointSize builtin if the shader is compiled into a render
        // pipeline that uses a non-point topology.
        // TODO (hao.x.li@intel.com): Remove this once WebGPU requires there is no
        // gl_PointSize builtin (https://github.com/gpuweb/gpuweb/issues/332).
        options_msl.enable_point_size_builtin = false;

        // Always use vertex buffer 30 (the last one in the vertex buffer table) to contain
        // the shader storage buffer lengths.
        options_msl.buffer_size_buffer_index = kBufferLengthBufferSlot;

        options_msl.additional_fixed_sample_mask = sampleMask;

        spirv_cross::CompilerMSL compiler(*spirv);
        compiler.set_msl_options(options_msl);
        compiler.set_entry_point(entryPointName, executionModel);

        // By default SPIRV-Cross will give MSL resources indices in increasing order.
        // To make the MSL indices match the indices chosen in the PipelineLayout, we build
        // a table of MSLResourceBinding to give to SPIRV-Cross.

        // Create one resource binding entry per stage per binding.
        for (BindGroupIndex group : IterateBitSet(layout->GetBindGroupLayoutsMask())) {
            const BindGroupLayoutBase::BindingMap& bindingMap =
                layout->GetBindGroupLayout(group)->GetBindingMap();

            for (const auto& it : bindingMap) {
                BindingNumber bindingNumber = it.first;
                BindingIndex bindingIndex = it.second;

                const BindingInfo& bindingInfo =
                    layout->GetBindGroupLayout(group)->GetBindingInfo(bindingIndex);

                if (!(bindingInfo.visibility & StageBit(stage))) {
                    continue;
                }

                uint32_t shaderIndex = layout->GetBindingIndexInfo(stage)[group][bindingIndex];

                spirv_cross::MSLResourceBinding mslBinding;
                mslBinding.stage = executionModel;
                mslBinding.desc_set = static_cast<uint32_t>(group);
                mslBinding.binding = static_cast<uint32_t>(bindingNumber);
                mslBinding.msl_buffer = mslBinding.msl_texture = mslBinding.msl_sampler =
                    shaderIndex;

                compiler.add_msl_resource_binding(mslBinding);
            }
        }

#ifdef DAWN_ENABLE_WGSL
        // Add vertex buffers bound as storage buffers
        if (GetDevice()->IsToggleEnabled(Toggle::MetalEnableVertexPulling) &&
            stage == SingleShaderStage::Vertex) {
            for (uint32_t dawnIndex : IterateBitSet(renderPipeline->GetVertexBufferSlotsUsed())) {
                uint32_t metalIndex = renderPipeline->GetMtlVertexBufferIndex(dawnIndex);

                spirv_cross::MSLResourceBinding mslBinding;

                mslBinding.stage = spv::ExecutionModelVertex;
                mslBinding.desc_set = kPullingBufferBindingSet;
                mslBinding.binding = dawnIndex;
                mslBinding.msl_buffer = metalIndex;
                compiler.add_msl_resource_binding(mslBinding);
            }
        }
#endif

        {
            // SPIRV-Cross also supports re-ordering attributes but it seems to do the correct thing
            // by default.
            NSString* mslSource;
            std::string msl = compiler.compile();

            // Some entry point names are forbidden in MSL so SPIRV-Cross modifies them. Query the
            // modified entryPointName from it.
            const std::string& modifiedEntryPointName =
                compiler.get_entry_point(entryPointName, executionModel).name;

            // Metal uses Clang to compile the shader as C++14. Disable everything in the -Wall
            // category. -Wunused-variable in particular comes up a lot in generated code, and some
            // (old?) Metal drivers accidentally treat it as a MTLLibraryErrorCompileError instead
            // of a warning.
            msl = R"(\
#ifdef __clang__
#pragma clang diagnostic ignored "-Wall"
#endif
)" + msl;
            mslSource = [[NSString alloc] initWithUTF8String:msl.c_str()];

            auto mtlDevice = ToBackend(GetDevice())->GetMTLDevice();
            NSError* error = nil;
            id<MTLLibrary> library = [mtlDevice newLibraryWithSource:mslSource
                                                             options:nil
                                                               error:&error];
            if (error != nil) {
                if (error.code != MTLLibraryErrorCompileWarning) {
                    const char* errorString = [error.localizedDescription UTF8String];
                    return DAWN_VALIDATION_ERROR(std::string("Unable to create library object: ") +
                                                 errorString);
                }
            }

            NSString* name = [[NSString alloc] initWithUTF8String:modifiedEntryPointName.c_str()];
            out->function = [library newFunctionWithName:name];
            [library release];
        }

        out->needsStorageBufferLength = compiler.needs_buffer_size_buffer();

        if (GetDevice()->IsToggleEnabled(Toggle::MetalEnableVertexPulling) &&
            GetEntryPoint(entryPointName, stage).usedVertexAttributes.any()) {
            out->needsStorageBufferLength = true;
        }

        return {};
    }
}}  // namespace dawn_native::metal