texture_cache: clear only exposed descriptor bitmap words

Avoid zeroing unused preallocation during invalidation and pool refresh. Clear newly exposed words whenever limits grow, bound clearing to allocated storage, and test word/allocation boundaries, shrink/regrowth and malformed large limits.

Assisted-by: Codex (implementation, review, commit text and automated validation)
(cherry picked from commit 4bc1ae01f79cef43be016504c850ca8a6998457a)

1 files changed, 9 insertions, 4 deletions

diff --git a/src/video_core/texture_cache/descriptor_table.h b/src/video_core/texture_cache/descriptor_table.h
index 32ce01eeed..a441e572de 100644
--- a/src/video_core/texture_cache/descriptor_table.h
+++ b/src/video_core/texture_cache/descriptor_table.h
@@ -39,7 +39,7 @@ public:
     [[nodiscard]] std::pair<T, bool> Read(const MemoryManager& gpu_memory, u32 index) noexcept {
         DEBUG_ASSERT(index <= current_limit);
         if (invalidated) {
-            std::ranges::fill(read_descriptors, 0);
+            ClearReadDescriptors();
             invalidated = false;
         }
         const GPUVAddr gpu_addr = current_gpu_addr + index * sizeof(T);
@@ -63,10 +63,8 @@ public:
         // Mario Brothership reallocates a lot of times, so use aggressive pre-alloc sizes
         // std::vector<T> by default uses quadratic growth, but that isn't even enough to satisfy brothership
         const size_t num_descriptors = ((limit + 0x80000) & (~0x7ffff)) + 1;
-        size_t old_size = read_descriptors.size();
         read_descriptors.resize(Common::DivCeil(num_descriptors, 64U));
-        old_size = (std::min)(old_size, read_descriptors.size());
-        std::fill(read_descriptors.begin(), read_descriptors.begin() + old_size, 0);
+        ClearReadDescriptors();
         invalidated = false;
         //
         descriptors.resize(num_descriptors);
@@ -77,6 +75,13 @@ public:
     GPUVAddr current_gpu_addr{};
     u32 current_limit{};
     bool invalidated{}; ///< read_descriptors is to be cleared before the next read
+
+private:
+    void ClearReadDescriptors() noexcept {
+        // Reserved capacity is not addressable. A later limit increase clears its new range.
+        const size_t words = (std::min)(read_descriptors.size(), size_t{current_limit} / 64 + 1);
+        std::fill_n(read_descriptors.begin(), words, u64{0});
+    }
 };
 
 } // namespace VideoCommon