[Impeller] Patch the compiler to account for subpass inputs and PSO metadata. (#45739)

Towards flutter/flutter#128911

Drive by fixes flutter/flutter#123795

Author: chinmaygarde

impeller/aiks/aiks_unittests.cc

@@ -1636,7 +1636,7 @@ TEST_P(AiksTest, ColorWheel) {
   auto callback = [&](AiksContext& renderer) -> std::optional<Picture> {
     // UI state.
     static bool cache_the_wheel = true;
-    static int current_blend_index = 3;
+    static int current_blend_index = 14;
     static float dst_alpha = 1;
     static float src_alpha = 1;
     static Color color0 = Color::Red();

impeller/compiler/code_gen_template.h

@@ -173,20 +173,30 @@ std::move({{ arg.argument_name }}){% if not loop.is_last %}, {% endif %}
   // ===========================================================================
   // Metadata for Vulkan =======================================================
   // ===========================================================================
-  static constexpr std::array<DescriptorSetLayout,{{length(buffers)+length(sampled_images)}}> kDescriptorSetLayouts{
+  static constexpr std::array<DescriptorSetLayout,{{length(buffers)+length(sampled_images)+length(subpass_inputs)}}> kDescriptorSetLayouts{
 {% for buffer in buffers %}
     DescriptorSetLayout{
       {{buffer.binding}}, // binding = {{buffer.binding}}
+      {{buffer.input_attachment_index}}, // input_attachment_index = {{buffer.input_attachment_index}}
       {{buffer.descriptor_type}}, // descriptor_type = {{buffer.descriptor_type}}
       {{to_shader_stage(shader_stage)}}, // shader_stage = {{to_shader_stage(shader_stage)}}
     },
 {% endfor %}
 {% for sampled_image in sampled_images %}
     DescriptorSetLayout{
       {{sampled_image.binding}}, // binding = {{sampled_image.binding}}
+      {{sampled_image.input_attachment_index}}, // input_attachment_index = {{sampled_image.input_attachment_index}}
       {{sampled_image.descriptor_type}}, // descriptor_type = {{sampled_image.descriptor_type}}
       {{to_shader_stage(shader_stage)}}, // shader_stage = {{to_shader_stage(shader_stage)}}
     },
+{% endfor %}
+{% for subpass_input in subpass_inputs %}
+    DescriptorSetLayout{
+      {{subpass_input.binding}}, // binding = {{subpass_input.binding}}
+      {{subpass_input.input_attachment_index}}, // input_attachment_index = {{subpass_input.input_attachment_index}}
+      {{subpass_input.descriptor_type}}, // descriptor_type = {{subpass_input.descriptor_type}}
+      {{to_shader_stage(shader_stage)}}, // shader_stage = {{to_shader_stage(shader_stage)}}
+    },
 {% endfor %}
   };
 

impeller/compiler/compiler.cc

@@ -115,15 +115,13 @@ static CompilerBackend CreateMSLCompiler(
 static CompilerBackend CreateVulkanCompiler(
     const spirv_cross::ParsedIR& ir,
     const SourceOptions& source_options) {
-  // TODO(dnfield): It seems like what we'd want is a CompilerGLSL with
-  // vulkan_semantics set to true, but that has regressed some things on GLES
-  // somehow. In the mean time, go back to using CompilerMSL, but set the Metal
-  // Language version to something really high so that we don't get weird
-  // complaints about using Metal features while trying to build Vulkan shaders.
-  // https://github.com/flutter/flutter/issues/123795
-  return CreateMSLCompiler(
-      ir, source_options,
-      spirv_cross::CompilerMSL::Options::make_msl_version(3, 0, 0));
+  auto vk_compiler = std::make_shared<spirv_cross::CompilerGLSL>(ir);
+  spirv_cross::CompilerGLSL::Options sl_options;
+  sl_options.vulkan_semantics = true;
+  sl_options.force_zero_initialized_variables = true;
+  sl_options.es = false;
+  vk_compiler->set_common_options(sl_options);
+  return CompilerBackend(vk_compiler);
 }
 
 static CompilerBackend CreateGLSLCompiler(const spirv_cross::ParsedIR& ir,
@@ -218,6 +216,7 @@ static CompilerBackend CreateCompiler(const spirv_cross::ParsedIR& ir,
       break;
     case TargetPlatform::kSkSL:
       compiler = CreateSkSLCompiler(ir, source_options);
+      break;
   }
   if (!compiler) {
     return {};

impeller/compiler/compiler_backend.cc

@@ -4,6 +4,8 @@
 
 #include "impeller/compiler/compiler_backend.h"
 
+#include <limits>
+
 #include "impeller/base/comparable.h"
 
 namespace impeller {
@@ -44,8 +46,7 @@ uint32_t CompilerBackend::GetExtendedMSLResourceBinding(
   if (auto compiler = GetGLSLCompiler()) {
     return compiler->get_decoration(id, spv::Decoration::DecorationBinding);
   }
-  const auto kOOBIndex = static_cast<uint32_t>(-1);
-  return kOOBIndex;
+  return std::numeric_limits<uint32_t>::max();
 }
 
 const spirv_cross::Compiler* CompilerBackend::GetCompiler() const {

impeller/compiler/reflector.cc

@@ -7,6 +7,7 @@
 #include "impeller/compiler/reflector.h"
 
 #include <atomic>
+#include <limits>
 #include <optional>
 #include <set>
 #include <sstream>
@@ -216,9 +217,9 @@ std::optional<nlohmann::json> Reflector::GenerateTemplateArguments() const {
     if (auto storage_buffers_json =
             ReflectResources(shader_resources.storage_buffers);
         storage_buffers_json.has_value()) {
-      for (auto uniform_buffer : storage_buffers_json.value()) {
-        uniform_buffer["descriptor_type"] = "DescriptorType::kStorageBuffer";
-        buffers.emplace_back(std::move(uniform_buffer));
+      for (auto storage_buffer : storage_buffers_json.value()) {
+        storage_buffer["descriptor_type"] = "DescriptorType::kStorageBuffer";
+        buffers.emplace_back(std::move(storage_buffer));
       }
     } else {
       return std::nullopt;
@@ -261,6 +262,19 @@ std::optional<nlohmann::json> Reflector::GenerateTemplateArguments() const {
     }
   }
 
+  {
+    if (auto inputs = ReflectResources(shader_resources.subpass_inputs);
+        inputs.has_value()) {
+      auto& subpass_inputs = root["subpass_inputs"] = nlohmann::json::array_t{};
+      for (auto input : inputs.value()) {
+        input["descriptor_type"] = "DescriptorType::kSubpassInput";
+        subpass_inputs.emplace_back(std::move(input));
+      }
+    } else {
+      return std::nullopt;
+    }
+  }
+
   if (auto stage_outputs = ReflectResources(shader_resources.stage_outputs);
       stage_outputs.has_value()) {
     root["stage_outputs"] = std::move(stage_outputs.value());
@@ -431,6 +445,14 @@ std::vector<size_t> Reflector::ComputeOffsets(
   return offsets;
 }
 
+static uint32_t GetResourceDecorationIfPresent(const CompilerBackend& compiler,
+                                               spirv_cross::ID id,
+                                               spv::Decoration decoration) {
+  return compiler->has_decoration(id, decoration)
+             ? compiler->get_decoration(id, decoration)
+             : std::numeric_limits<uint32_t>::max();
+}
+
 std::optional<nlohmann::json::object_t> Reflector::ReflectResource(
     const spirv_cross::Resource& resource,
     std::optional<size_t> offset) const {
@@ -445,6 +467,8 @@ std::optional<nlohmann::json::object_t> Reflector::ReflectResource(
       resource.id, spv::Decoration::DecorationDescriptorSet);
   result["location"] = compiler_->get_decoration(
       resource.id, spv::Decoration::DecorationLocation);
+  result["input_attachment_index"] = GetResourceDecorationIfPresent(
+      compiler_, resource.id, spv::Decoration::DecorationInputAttachmentIndex);
   result["index"] =
       compiler_->get_decoration(resource.id, spv::Decoration::DecorationIndex);
   result["ext_res_0"] = compiler_.GetExtendedMSLResourceBinding(

impeller/core/shader_types.h

@@ -5,6 +5,7 @@
 #pragma once
 
 #include <cstddef>
+#include <limits>
 #include <optional>
 #include <string_view>
 #include <vector>
@@ -144,12 +145,21 @@ enum class DescriptorType {
   kSampledImage,
   kImage,
   kSampler,
+  kSubpassInput,
 };
 
 struct DescriptorSetLayout {
   uint32_t binding;
+  uint32_t input_attachment_index;
   DescriptorType descriptor_type;
   ShaderStage shader_stage;
+
+  constexpr std::optional<uint32_t> GetInputAttachmentIndexIfValid() const {
+    if (std::numeric_limits<uint32_t>::max() == input_attachment_index) {
+      return std::nullopt;
+    }
+    return input_attachment_index;
+  }
 };
 
 template <size_t Size>

impeller/playground/backend/vulkan/playground_impl_vk.cc

@@ -13,6 +13,7 @@
 #include "flutter/fml/logging.h"
 #include "flutter/fml/mapping.h"
 #include "impeller/entity/vk/entity_shaders_vk.h"
+#include "impeller/entity/vk/framebuffer_blend_shaders_vk.h"
 #include "impeller/entity/vk/modern_shaders_vk.h"
 #include "impeller/fixtures/vk/fixtures_shaders_vk.h"
 #include "impeller/playground/imgui/vk/imgui_shaders_vk.h"
@@ -33,6 +34,9 @@ ShaderLibraryMappingsForPlayground() {
                                              impeller_entity_shaders_vk_length),
       std::make_shared<fml::NonOwnedMapping>(impeller_modern_shaders_vk_data,
                                              impeller_modern_shaders_vk_length),
+      std::make_shared<fml::NonOwnedMapping>(
+          impeller_framebuffer_blend_shaders_vk_data,
+          impeller_framebuffer_blend_shaders_vk_length),
       std::make_shared<fml::NonOwnedMapping>(
           impeller_fixtures_shaders_vk_data,
           impeller_fixtures_shaders_vk_length),

impeller/renderer/backend/vulkan/descriptor_pool_vk.cc

@@ -24,7 +24,9 @@ static vk::UniqueDescriptorPool CreatePool(const vk::Device& device,
   std::vector<vk::DescriptorPoolSize> pools = {
       {vk::DescriptorType::eCombinedImageSampler, pool_count},
       {vk::DescriptorType::eUniformBuffer, pool_count},
-      {vk::DescriptorType::eStorageBuffer, pool_count}};
+      {vk::DescriptorType::eStorageBuffer, pool_count},
+      {vk::DescriptorType::eInputAttachment, pool_count},
+  };
 
   vk::DescriptorPoolCreateInfo pool_info;
   pool_info.setMaxSets(pools.size() * pool_count);

impeller/renderer/backend/vulkan/formats_vk.h

@@ -274,21 +274,17 @@ constexpr vk::DescriptorType ToVKDescriptorType(DescriptorType type) {
   switch (type) {
     case DescriptorType::kSampledImage:
       return vk::DescriptorType::eCombinedImageSampler;
-      break;
     case DescriptorType::kUniformBuffer:
       return vk::DescriptorType::eUniformBuffer;
-      break;
     case DescriptorType::kStorageBuffer:
       return vk::DescriptorType::eStorageBuffer;
-      break;
     case DescriptorType::kImage:
       return vk::DescriptorType::eSampledImage;
-      break;
     case DescriptorType::kSampler:
       return vk::DescriptorType::eSampler;
-      break;
+    case DescriptorType::kSubpassInput:
+      return vk::DescriptorType::eInputAttachment;
   }
-
   FML_UNREACHABLE();
 }
 

shell/platform/embedder/embedder_surface_metal_impeller.mm

@@ -11,7 +11,7 @@
 #include "flutter/fml/synchronization/sync_switch.h"
 #include "flutter/shell/gpu/gpu_surface_metal_delegate.h"
 #include "flutter/shell/gpu/gpu_surface_metal_impeller.h"
-#import "flutter/shell/platform/darwin/graphics/FlutterDarwinContextMetalImpeller.h"
+#include "flutter/shell/platform/darwin/graphics/FlutterDarwinContextMetalImpeller.h"
 #include "impeller/entity/mtl/entity_shaders.h"
 #include "impeller/entity/mtl/framebuffer_blend_shaders.h"
 #include "impeller/entity/mtl/modern_shaders.h"