diff --git a/libcxx/include/__memory_resource/memory_resource.h b/libcxx/include/__memory_resource/memory_resource.h
--- a/libcxx/include/__memory_resource/memory_resource.h
+++ b/libcxx/include/__memory_resource/memory_resource.h
@@ -32,11 +32,13 @@
 public:
   virtual ~memory_resource() = default;
 
-  _LIBCPP_HIDE_FROM_ABI void* allocate(size_t __bytes, size_t __align = __max_align) {
+  [[using __gnu__: __returns_nonnull__, __alloc_size__(2), __alloc_align__(3)]] _LIBCPP_HIDE_FROM_ABI void*
+  allocate(size_t __bytes, size_t __align = __max_align) {
     return do_allocate(__bytes, __align);
   }
 
-  _LIBCPP_HIDE_FROM_ABI void deallocate(void* __p, size_t __bytes, size_t __align = __max_align) {
+  [[__gnu__::__nonnull__]] _LIBCPP_HIDE_FROM_ABI void
+  deallocate(void* __p, size_t __bytes, size_t __align = __max_align) {
     do_deallocate(__p, __bytes, __align);
   }
 
@@ -61,10 +63,14 @@
 
 // [mem.res.global]
 
-_LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource* get_default_resource() noexcept;
-_LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource* set_default_resource(memory_resource*) noexcept;
-_LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource* new_delete_resource() noexcept;
-_LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource* null_memory_resource() noexcept;
+[[using __gnu__: __returns_nonnull__, __pure__]] _LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource*
+get_default_resource() noexcept;
+[[using __gnu__: __returns_nonnull__, __pure__]] _LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource*
+set_default_resource(memory_resource*) noexcept;
+[[using __gnu__: __returns_nonnull__, __const__]] _LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource*
+new_delete_resource() noexcept;
+[[using __gnu__: __returns_nonnull__, __const__]] _LIBCPP_AVAILABILITY_MEMORY_RESOURCE _LIBCPP_FUNC_VIS memory_resource*
+null_memory_resource() noexcept;
 
 } // namespace pmr
 
diff --git a/libcxx/include/__memory_resource/unsynchronized_pool_resource.h b/libcxx/include/__memory_resource/unsynchronized_pool_resource.h
--- a/libcxx/include/__memory_resource/unsynchronized_pool_resource.h
+++ b/libcxx/include/__memory_resource/unsynchronized_pool_resource.h
@@ -75,11 +75,11 @@
 
   unsynchronized_pool_resource& operator=(const unsynchronized_pool_resource&) = delete;
 
-  _LIBCPP_AVAILABILITY_MEMORY_RESOURCE void release();
+  [[__gnu__::__pure__]] _LIBCPP_AVAILABILITY_MEMORY_RESOURCE void release();
 
   _LIBCPP_HIDE_FROM_ABI memory_resource* upstream_resource() const { return __res_; }
 
-  _LIBCPP_AVAILABILITY_MEMORY_RESOURCE pool_options options() const;
+  [[__gnu__::__pure__]] _LIBCPP_AVAILABILITY_MEMORY_RESOURCE pool_options options() const;
 
 protected:
   _LIBCPP_AVAILABILITY_MEMORY_RESOURCE void* do_allocate(size_t __bytes, size_t __align) override; // key function