host_shaders: More proper handling of x2 MSAA copies

src/video_core/host_shaders/convert_msaa_to_non_msaa.comp

@@ -15,11 +15,14 @@ void main() {
 
     // TODO: Specialization constants for num_samples?
     const int num_samples = imageSamples(msaa_in);
+    const ivec3 msaa_size = imageSize(msaa_in);
+    const ivec3 out_size = imageSize(output_img);
+    const ivec3 scale = out_size / msaa_size;
     for (int curr_sample = 0; curr_sample < num_samples; ++curr_sample) {
         const vec4 pixel = imageLoad(msaa_in, coords, curr_sample);
 
-        const int single_sample_x = 2 * coords.x + (curr_sample & 1);
-        const int single_sample_y = 2 * coords.y + ((curr_sample / 2) & 1);
+        const int single_sample_x = scale.x * coords.x + (curr_sample & 1);
+        const int single_sample_y = scale.y * coords.y + ((curr_sample / 2) & 1);
         const ivec3 dest_coords = ivec3(single_sample_x, single_sample_y, coords.z);
 
         if (any(greaterThanEqual(dest_coords, imageSize(output_img)))) {

src/video_core/host_shaders/convert_non_msaa_to_msaa.comp

@@ -15,9 +15,12 @@ void main() {
 
     // TODO: Specialization constants for num_samples?
     const int num_samples = imageSamples(output_msaa);
+    const ivec3 msaa_size = imageSize(output_msaa);
+    const ivec3 out_size = imageSize(img_in);
+    const ivec3 scale = out_size / msaa_size;
     for (int curr_sample = 0; curr_sample < num_samples; ++curr_sample) {
-        const int single_sample_x = 2 * coords.x + (curr_sample & 1);
-        const int single_sample_y = 2 * coords.y + ((curr_sample / 2) & 1);
+        const int single_sample_x = scale.x * coords.x + (curr_sample & 1);
+        const int single_sample_y = scale.y * coords.y + ((curr_sample / 2) & 1);
         const ivec3 single_coords = ivec3(single_sample_x, single_sample_y, coords.z);
 
         if (any(greaterThanEqual(single_coords, imageSize(img_in)))) {