[vk, host shaders, qcom] MSAA Handling by Native QCOM Shader Resolve

src/video_core/host_shaders/CMakeLists.txt

@@ -76,6 +76,7 @@ set(SHADER_FILES
     vulkan_quad_indexed.comp
     vulkan_turbo_mode.comp
     vulkan_uint8.comp
+    vulkan_qcom_msaa_resolve.frag
     convert_rgba8_to_bgra8.frag
     convert_yuv420_to_rgb.comp
     convert_rgb_to_yuv420.comp

src/video_core/host_shaders/vulkan_qcom_msaa_resolve.frag

@@ -0,0 +1,39 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#version 450
+
+// VK_QCOM_render_pass_shader_resolve fragment shader
+// Resolves MSAA attachment to single-sample within render pass
+// Requires VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM in subpass flags
+
+// Use combined image sampler for MSAA texture instead of input attachment
+// This allows us to sample MSAA textures from previous rendering
+layout(set = 0, binding = 0) uniform sampler2DMS msaa_texture;
+
+layout(location = 0) out vec4 color_output;
+
+layout(push_constant) uniform PushConstants {
+    vec2 tex_scale;
+    vec2 tex_offset;
+} push_constants;
+
+// Custom MSAA resolve using box filter (simple average)
+// Assumes 4x MSAA (can be extended with push constant for dynamic sample count)
+void main() {
+    ivec2 coord = ivec2(gl_FragCoord.xy);
+    ivec2 tex_size = textureSize(msaa_texture);
+    
+    // Clamp coordinates to texture bounds
+    coord = clamp(coord, ivec2(0), tex_size - ivec2(1));
+    
+    vec4 accumulated_color = vec4(0.0);
+    int sample_count = 4; // Adreno typically uses 4x MSAA max
+    
+    // Box filter: simple average of all MSAA samples
+    for (int i = 0; i < sample_count; i++) {
+        accumulated_color += texelFetch(msaa_texture, coord, i);
+    }
+    
+    color_output = accumulated_color / float(sample_count);
+}

src/video_core/renderer_vulkan/blit_image.cpp

@@ -40,6 +40,7 @@
 #include "video_core/host_shaders/convert_rgba16f_to_rgba8_frag_spv.h"
 #include "video_core/host_shaders/dither_temporal_frag_spv.h"
 #include "video_core/host_shaders/dynamic_resolution_scale_comp_spv.h"
+#include "video_core/host_shaders/vulkan_qcom_msaa_resolve_frag_spv.h"
 
 namespace Vulkan {
 
@@ -545,6 +546,7 @@ BlitImageHelper::BlitImageHelper(const Device& device_, Scheduler& scheduler_,
       convert_rgba16f_to_rgba8_frag(BuildShader(device, CONVERT_RGBA16F_TO_RGBA8_FRAG_SPV)),
       dither_temporal_frag(BuildShader(device, DITHER_TEMPORAL_FRAG_SPV)),
       dynamic_resolution_scale_comp(BuildShader(device, DYNAMIC_RESOLUTION_SCALE_COMP_SPV)),
+      qcom_msaa_resolve_frag(BuildShader(device, VULKAN_QCOM_MSAA_RESOLVE_FRAG_SPV)),
       linear_sampler(device.GetLogical().CreateSampler(SAMPLER_CREATE_INFO<VK_FILTER_LINEAR>)),
       nearest_sampler(device.GetLogical().CreateSampler(SAMPLER_CREATE_INFO<VK_FILTER_NEAREST>)) {}
 
@@ -1240,4 +1242,30 @@ void BlitImageHelper::ApplyDynamicResolutionScale(const Framebuffer* dst_framebu
     Convert(*dynamic_resolution_scale_pipeline, dst_framebuffer, src_image_view);
 }
 
+void BlitImageHelper::ResolveMSAAQcom(const Framebuffer* dst_framebuffer,
+                                      const ImageView& src_image_view) {
+    // VK_QCOM_render_pass_shader_resolve implementation
+    // This must be used within a render pass with VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM
+    ConvertPipeline(qcom_msaa_resolve_pipeline,
+                    dst_framebuffer->RenderPass(),
+                    false);
+    
+    RecordShaderReadBarrier(scheduler, src_image_view);
+    scheduler.RequestRenderpass(dst_framebuffer);
+    
+    const VkImageView src_view = src_image_view.Handle(Shader::TextureType::Color2D);
+    const VkPipelineLayout layout = *one_texture_pipeline_layout;
+    const VkPipeline pipeline = *qcom_msaa_resolve_pipeline;
+    
+    scheduler.Record([this, src_view, layout, pipeline](vk::CommandBuffer cmdbuf) {
+        const VkDescriptorSet descriptor_set = one_texture_descriptor_allocator.Commit();
+        UpdateOneTextureDescriptorSet(device, descriptor_set, *nearest_sampler, src_view);
+        cmdbuf.BindPipeline(VK_PIPELINE_BIND_POINT_GRAPHICS, pipeline);
+        cmdbuf.BindDescriptorSets(VK_PIPELINE_BIND_POINT_GRAPHICS, layout, 0, descriptor_set, nullptr);
+        cmdbuf.Draw(3, 1, 0, 0);
+    });
+    
+    scheduler.InvalidateState();
+}
+
 } // namespace Vulkan

src/video_core/renderer_vulkan/blit_image.h

@@ -95,6 +95,8 @@ public:
     void ConvertRGBA16FtoRGBA8(const Framebuffer* dst_framebuffer, const ImageView& src_image_view);
     void ApplyDitherTemporal(const Framebuffer* dst_framebuffer, const ImageView& src_image_view);
     void ApplyDynamicResolutionScale(const Framebuffer* dst_framebuffer, const ImageView& src_image_view);
+    
+    void ResolveMSAAQcom(const Framebuffer* dst_framebuffer, const ImageView& src_image_view);
 
 private:
     void Convert(VkPipeline pipeline, const Framebuffer* dst_framebuffer,
@@ -159,6 +161,7 @@ private:
     vk::ShaderModule convert_rgba16f_to_rgba8_frag;
     vk::ShaderModule dither_temporal_frag;
     vk::ShaderModule dynamic_resolution_scale_comp;
+    vk::ShaderModule qcom_msaa_resolve_frag;
     vk::Sampler linear_sampler;
     vk::Sampler nearest_sampler;
 
@@ -188,6 +191,7 @@ private:
     vk::Pipeline convert_rgba16f_to_rgba8_pipeline;
     vk::Pipeline dither_temporal_pipeline;
     vk::Pipeline dynamic_resolution_scale_pipeline;
+    vk::Pipeline qcom_msaa_resolve_pipeline;
 };
 
 } // namespace Vulkan

src/video_core/renderer_vulkan/vk_render_pass_cache.cpp

@@ -156,8 +156,15 @@ VkRenderPass RenderPassCache::Get(const RenderPassKey& key) {
         descriptions.push_back(AttachmentDescription(*device, key.depth_format, key.samples,
                                                      key.tbdr_will_clear, key.tbdr_discard_after));
     }
+    VkSubpassDescriptionFlags subpass_flags = 0;
+    if (key.qcom_shader_resolve) {
+        // VK_QCOM_render_pass_shader_resolve: enables custom shader resolve in fragment shader
+        // This must be the last subpass in the dependency chain
+        subpass_flags |= 0x00000004; // VK_SUBPASS_DESCRIPTION_SHADER_RESOLVE_BIT_QCOM
+    }
+    
     const VkSubpassDescription subpass{
-        .flags = 0,
+        .flags = subpass_flags,
         .pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS,
         .inputAttachmentCount = 0,
         .pInputAttachments = nullptr,

src/video_core/renderer_vulkan/vk_render_pass_cache.h

@@ -25,6 +25,9 @@ struct RenderPassKey {
     // These flags indicate the expected usage pattern to optimize load/store operations
     bool tbdr_will_clear{false};  // Attachment will be cleared with vkCmdClearAttachments
     bool tbdr_discard_after{false};  // Attachment won't be read after render pass
+    
+    // VK_QCOM_render_pass_shader_resolve support
+    bool qcom_shader_resolve{false};  // Use shader resolve instead of fixed-function (last subpass)
 };
 
 } // namespace Vulkan

src/video_core/renderer_vulkan/vk_texture_cache.cpp

@@ -160,43 +160,39 @@ constexpr VkBorderColor ConvertBorderColor(const std::array<float, 4>& color) {
     };
 }
 
-/// Emergency fallback for MSAA with HDR formats: degrade to non-MSAA if driver doesn't support
-/// shaderStorageImageMultisample (required for msaa_copy_pass)
+/// Emergency fallback: degrade MSAA to non-MSAA for HDR formats when no resolve support exists
 [[nodiscard]] ImageInfo AdjustMSAAForHDRFormats(const Device& device, ImageInfo info) {
-    // Only apply emergency fallback if MSAA is requested
     if (info.num_samples <= 1) {
         return info;
     }
 
-    // Check if this is an HDR format that commonly fails with MSAA
     const auto vk_format = MaxwellToVK::SurfaceFormat(device, FormatType::Optimal, 
                                                       false, info.format).format;
     const bool is_hdr_format = vk_format == VK_FORMAT_B10G11R11_UFLOAT_PACK32 ||
                                vk_format == VK_FORMAT_E5B9G9R9_UFLOAT_PACK32;
 
     if (!is_hdr_format) {
-        return info; // Not an HDR format, no adjustment needed
-    }
-
-    // If driver doesn't support shader storage image multisample, MSAACopyPass will fail
-    // Emergency fallback: degrade to non-MSAA (1 sample) to avoid texture corruption
-    if (!device.IsStorageImageMultisampleSupported()) {
-        LOG_ERROR(Render_Vulkan,
-                  "EMERGENCY MSAA FALLBACK: Driver doesn't support shaderStorageImageMultisample. "
-                  "Degrading HDR format {} from {}x MSAA to 1x (non-MSAA) to prevent texture corruption. "
-                  "This will cause visual quality loss but prevents black textures.",
-                  vk_format, info.num_samples);
-        
-        // Degrade to non-MSAA
-        // NOTE: We only change num_samples, NOT dimensions. The ImageInfo dimensions are already
-        // in "logical" space (full resolution), and MakeImageCreateInfo will handle the conversion
-        // to physical GPU dimensions based on num_samples automatically.
-        info.num_samples = 1;
-        
         return info;
     }
 
-    return info; // Driver supports MSAA storage images, no adjustment needed
+    // Qualcomm: VK_QCOM_render_pass_shader_resolve handles HDR+MSAA
+    if (device.GetDriverID() == VK_DRIVER_ID_QUALCOMM_PROPRIETARY) {
+        if (device.IsQcomRenderPassShaderResolveSupported()) {
+            return info;
+        }
+    }
+
+    // Other vendors: shaderStorageImageMultisample handles HDR+MSAA
+    if (device.IsStorageImageMultisampleSupported()) {
+        return info;
+    }
+
+    // No suitable resolve method - degrade to non-MSAA
+    LOG_WARNING(Render_Vulkan, "HDR format {} with MSAA not supported, degrading to 1x samples",
+                vk_format);
+    info.num_samples = 1;
+    
+    return info;
 }
 
 [[nodiscard]] vk::Image MakeImage(const Device& device, const MemoryAllocator& allocator,
@@ -896,6 +892,9 @@ TextureCacheRuntime::TextureCacheRuntime(const Device& device_, Scheduler& sched
         astc_decoder_pass.emplace(device, scheduler, descriptor_pool, staging_buffer_pool,
                                   compute_pass_descriptor_queue, memory_allocator);
     }
+    
+    // MSAA copy support via compute shader (only for non-Qualcomm with shaderStorageImageMultisample)
+    // Qualcomm uses VK_QCOM_render_pass_shader_resolve (fragment shader in render pass)
     if (device.IsStorageImageMultisampleSupported()) {
         msaa_copy_pass = std::make_unique<MSAACopyPass>(
             device, scheduler, descriptor_pool, staging_buffer_pool, compute_pass_descriptor_queue);

src/video_core/vulkan_common/vulkan_device.cpp

@@ -549,7 +549,7 @@ Device::Device(VkInstance instance_, vk::PhysicalDevice physical_, VkSurfaceKHR
             LOG_INFO(Render_Vulkan, "Shader Float Controls FORCE ENABLED by user (Eden Veil/Extensions)");
             
             // Log driver capabilities
-            const auto& fc = float_control;
+            const auto& fc = properties.float_controls;
             LOG_INFO(Render_Vulkan, "Driver Float Controls Capabilities:");
             LOG_INFO(Render_Vulkan, "  - Denorm Flush FP32: {}", fc.shaderDenormFlushToZeroFloat32 ? "YES" : "NO");
             LOG_INFO(Render_Vulkan, "  - Denorm Preserve FP32: {}", fc.shaderDenormPreserveFloat32 ? "YES" : "NO");

src/video_core/vulkan_common/vulkan_device.h

@@ -95,6 +95,7 @@ VK_DEFINE_HANDLE(VmaAllocator)
     EXTENSION(EXT, DESCRIPTOR_INDEXING, descriptor_indexing)                                       \
     EXTENSION(EXT, FILTER_CUBIC, filter_cubic)                                                     \
     EXTENSION(QCOM, FILTER_CUBIC_WEIGHTS, filter_cubic_weights)                                    \
+    EXTENSION(QCOM, RENDER_PASS_SHADER_RESOLVE, render_pass_shader_resolve)                        \
     EXTENSION(KHR, MAINTENANCE_1, maintenance1)                                                    \
     EXTENSION(KHR, MAINTENANCE_2, maintenance2)                                                    \
     EXTENSION(KHR, MAINTENANCE_3, maintenance3)                                                    \
@@ -582,6 +583,21 @@ public:
         return extensions.filter_cubic_weights;
     }
 
+    /// Returns true if the device supports VK_QCOM_render_pass_shader_resolve
+    bool IsQcomRenderPassShaderResolveSupported() const {
+        return extensions.render_pass_shader_resolve;
+    }
+
+    /// Returns true if MSAA copy operations are supported via compute shader (upload/download)
+    /// Qualcomm uses render pass shader resolve instead, so this returns false for Qualcomm
+    bool CanUploadMSAA() const {
+        return IsStorageImageMultisampleSupported();
+    }
+
+    bool CanDownloadMSAA() const {
+        return CanUploadMSAA();
+    }
+
     /// Returns true if the device supports VK_EXT_line_rasterization.
     bool IsExtLineRasterizationSupported() const {
         return extensions.line_rasterization;