Keep huge ASTC arrays from a lower mip on the host (title 1 terrain)

Title 1's terrain virtual textures are 8192x8192x68 ASTC 8x8 sRGB arrays with
12 levels: 1.5 GB in guest memory (fully backed) but 23 GB each as the RGBA8
Eden decodes ASTC to, so they were created unbacked and the near terrain
sampled black. A GPU-decoded ASTC 2D array over 1 GiB decoded now keeps only
the levels from the first one that fits in 512 MiB (here 3: 1024x1024, 380
MiB); host mip 0 is that guest level. Uploads read each layer's tail of the
mip chain into a compact buffer and decode only those levels, views shift
their level range, and these images are never downloaded. Normalized
coordinates and derivative LOD address the smaller image correctly; the
nearest terrain is lower resolution than on the console.

Also logs how unbacked images are used (views, render targets, blits, DMA).

1 files changed, 4 insertions, 0 deletions

diff --git a/src/video_core/texture_cache/image_base.h b/src/video_core/texture_cache/image_base.h
index 846a6f7fc1..d0af53631d 100644
--- a/src/video_core/texture_cache/image_base.h
+++ b/src/video_core/texture_cache/image_base.h
@@ -46,6 +46,9 @@ enum class ImageFlagBits : u32 {
     AsynchronousDecode = 1 << 16,
     IsDecoding = 1 << 17, ///< Is currently being decoded asynchronously.
     Unbacked = 1 << 18,   ///< Host image has no memory (too big to back); never upload/download.
+    /// The host image keeps only mip levels >= host_level_offset (its decoded copy would not fit
+    /// in VRAM); uploads skip the rest, downloads are never done.
+    TrimmedLevels = 1 << 19,
 };
 DECLARE_ENUM_FLAG_OPERATORS(ImageFlagBits)
 
@@ -94,6 +97,7 @@ struct ImageBase {
     u32 unswizzled_size_bytes = 0;
     u32 converted_size_bytes = 0;
     u32 scale_rating = 0;
+    u32 host_level_offset = 0; ///< Guest mip level held by host mip 0 (see TrimmedLevels).
     u64 scale_tick = 0;
     bool has_scaled = false;