Vulkan: implement D24S8 <-> RGBA8 convertions.

src/video_core/host_shaders/CMakeLists.txt

@@ -10,6 +10,8 @@ set(SHADER_FILES
     astc_decoder.comp
     block_linear_unswizzle_2d.comp
     block_linear_unswizzle_3d.comp
+    convert_abgr8_to_d24s8.frag
+    convert_d24s8_to_abgr8.frag
     convert_depth_to_float.frag
     convert_float_to_depth.frag
     full_screen_triangle.vert

src/video_core/host_shaders/convert_abgr8_to_d24s8.frag

@@ -0,0 +1,17 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#version 450
+// #extension GL_ARB_shader_stencil_export : require
+
+layout(binding = 0) uniform sampler2D color_texture;
+
+void main() {
+    ivec2 coord = ivec2(gl_FragCoord.xy);
+    uvec4 color = uvec4(texelFetch(color_texture, coord, 0).rgba * (exp2(8) - 1.0f));
+    uint depth_unorm = (color.r << 16) | (color.g << 8) | color.b;
+
+    gl_FragDepth = float(depth_unorm) / (exp2(24.0) - 1.0f);
+    // gl_FragStencilRefARB = int(color.a);
+}

src/video_core/host_shaders/convert_d24s8_to_abgr8.frag

@@ -0,0 +1,21 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#version 450
+
+layout(binding = 0) uniform sampler2D depth_tex;
+layout(binding = 1) uniform isampler2D stencil_tex;
+
+layout(location = 0) out vec4 color;
+
+void main() {
+    ivec2 coord = ivec2(gl_FragCoord.xy);
+    uint depth = uint(textureLod(depth_tex, coord, 0).r * (exp2(24.0) - 1.0f));
+    uint stencil = uint(textureLod(stencil_tex, coord, 0).r);
+
+    color.r = float(depth >> 16) / (exp2(8) - 1.0);
+    color.g = float((depth >> 8) & 0x00FF) / (exp2(8) - 1.0);
+    color.b = float(depth & 0x00FF) / (exp2(8) - 1.0);
+    color.a = float(stencil) / (exp2(8) - 1.0);
+}