[GPU] Avoid stale texture state after invalidation

Check shared memory validity before marking textures up to date and installing watches. If the backing range was invalidated, leave the texture outdated so it can be reloaded later.

src/xenia/gpu/shared_memory.cc

@@ -416,6 +416,34 @@ bool SharedMemory::RequestRange(uint32_t start, uint32_t length) {
   return UploadRanges(uploads, current_upload_range);
 }
 
+bool SharedMemory::IsRangeValid(uint32_t start, uint32_t length) const {
+  if (!length) {
+    return true;
+  }
+  if (start > kBufferSize || (kBufferSize - start) < length) {
+    return false;
+  }
+
+  const uint32_t page_first = start >> page_size_log2_;
+  const uint32_t page_last = (start + length - 1) >> page_size_log2_;
+  const uint32_t block_first = page_first >> 6;
+  const uint32_t block_last = page_last >> 6;
+
+  for (uint32_t i = block_first; i <= block_last; ++i) {
+    uint64_t valid_mask = UINT64_MAX;
+    if (i == block_first) {
+      valid_mask &= ~((uint64_t(1) << (page_first & 63)) - 1);
+    }
+    if (i == block_last && (page_last & 63) != 63) {
+      valid_mask &= (uint64_t(1) << ((page_last & 63) + 1)) - 1;
+    }
+    if ((system_page_flags_valid_[i] & valid_mask) != valid_mask) {
+      return false;
+    }
+  }
+  return true;
+}
+
 template <typename T>
 XE_FORCEINLINE XE_NOALIAS static T mod_shift_left(T value, uint32_t by) {
 #if XE_ARCH_AMD64 == 1