[vulkan] Implement push descriptors for compute pipelines

Implements push descriptor for compute pipelines along with a bug fix, the increment logic was, offset += sizeof(DescriptorUpdateEntry); 
This only advances the byte offset by a single descriptor slot, regardless of the array's size (descriptorCount).Now suppose if a shader utilized an array of descriptors (eg, layout(binding = 0) uniform sampler2D textures[4]) and if this happened to fit within the MaxPushDescriptors limit, the template would consume 4 * sizeof(DescriptorUpdateEntry) bytes, but the offset for the next binding would only advance by 1 slot.

src/video_core/renderer_vulkan/pipeline_helper.h

@@ -61,7 +61,8 @@ public:
             .pDescriptorUpdateEntries = entries.data(),
             .templateType = type,
             .descriptorSetLayout = descriptor_set_layout,
-            .pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS,
+            .pipelineBindPoint =
+                is_compute ? VK_PIPELINE_BIND_POINT_COMPUTE : VK_PIPELINE_BIND_POINT_GRAPHICS,
             .pipelineLayout = pipeline_layout,
             .set = 0,
         });
@@ -122,7 +123,7 @@ private:
             });
             ++binding;
             num_descriptors += descriptors[i].count;
-            offset += sizeof(DescriptorUpdateEntry);
+            offset += sizeof(DescriptorUpdateEntry) * descriptors[i].count;
         }
     }
 

src/video_core/renderer_vulkan/vk_compute_pipeline.cpp

@@ -50,11 +50,14 @@ ComputePipeline::ComputePipeline(const Device& device_, vk::PipelineCache& pipel
         DescriptorLayoutBuilder builder{device};
         builder.Add(info, VK_SHADER_STAGE_COMPUTE_BIT);
 
-        descriptor_set_layout = builder.CreateDescriptorSetLayout(false);
+        uses_push_descriptor = builder.CanUsePushDescriptor();
+        descriptor_set_layout = builder.CreateDescriptorSetLayout(uses_push_descriptor);
         pipeline_layout = builder.CreatePipelineLayout(*descriptor_set_layout);
         descriptor_update_template =
-            builder.CreateTemplate(*descriptor_set_layout, *pipeline_layout, false);
-        descriptor_allocator = descriptor_pool.Allocator(*descriptor_set_layout, info);
+            builder.CreateTemplate(*descriptor_set_layout, *pipeline_layout, uses_push_descriptor);
+        if (!uses_push_descriptor) {
+            descriptor_allocator = descriptor_pool.Allocator(*descriptor_set_layout, info);
+        }
         const VkPipelineShaderStageRequiredSubgroupSizeCreateInfoEXT subgroup_size_ci{
             .sType = VK_STRUCTURE_TYPE_PIPELINE_SHADER_STAGE_REQUIRED_SUBGROUP_SIZE_CREATE_INFO_EXT,
             .pNext = nullptr,
@@ -241,11 +244,16 @@ void ComputePipeline::Configure(Tegra::Engines::KeplerCompute& kepler_compute,
                                  RESCALING_LAYOUT_WORDS_OFFSET, sizeof(rescaling_data),
                                  rescaling_data.data());
         }
-        const VkDescriptorSet descriptor_set{descriptor_allocator.Commit()};
-        const vk::Device& dev{device.GetLogical()};
-        dev.UpdateDescriptorSet(descriptor_set, *descriptor_update_template, descriptor_data);
-        cmdbuf.BindDescriptorSets(VK_PIPELINE_BIND_POINT_COMPUTE, *pipeline_layout, 0,
-                                  descriptor_set, nullptr);
+        if (uses_push_descriptor) {
+            cmdbuf.PushDescriptorSetWithTemplateKHR(*descriptor_update_template, *pipeline_layout,
+                                                    0, descriptor_data);
+        } else {
+            const VkDescriptorSet descriptor_set{descriptor_allocator.Commit()};
+            const vk::Device& dev{device.GetLogical()};
+            dev.UpdateDescriptorSet(descriptor_set, *descriptor_update_template, descriptor_data);
+            cmdbuf.BindDescriptorSets(VK_PIPELINE_BIND_POINT_COMPUTE, *pipeline_layout, 0,
+                                      descriptor_set, nullptr);
+        }
     });
 }
 

src/video_core/renderer_vulkan/vk_compute_pipeline.h

@@ -55,6 +55,7 @@ private:
 
     vk::ShaderModule spv_module;
     vk::DescriptorSetLayout descriptor_set_layout;
+    bool uses_push_descriptor{false};
     DescriptorAllocator descriptor_allocator;
     vk::PipelineLayout pipeline_layout;
     vk::DescriptorUpdateTemplate descriptor_update_template;