Avoid some redundant checks in GetLiveResource

* Historically we always expected a live resource, but with descriptors that can
  be stale we can have a lot of queries where it's fine to just get NULL back if
  the resource doesn't exist.

renderdoc/core/resource_manager.h

@@ -638,7 +638,7 @@ public:
   // Live resources to replace serialised IDs
   void AddLiveResource(ResourceId origid, WrappedResourceType livePtr);
   bool HasLiveResource(ResourceId origid);
-  WrappedResourceType GetLiveResource(ResourceId origid);
+  WrappedResourceType GetLiveResource(ResourceId origid, bool optional = false);
   void EraseLiveResource(ResourceId origid);
 
   // when asked for a given id, return the resource for a replacement id
@@ -1816,20 +1816,31 @@ bool ResourceManager<Configuration>::HasLiveResource(ResourceId origid)
 
 template <typename Configuration>
 typename Configuration::WrappedResourceType ResourceManager<Configuration>::GetLiveResource(
-    ResourceId origid)
+    ResourceId origid, bool optional)
 {
   SCOPED_LOCK_OPTIONAL(m_Lock, m_Capturing);
 
   if(origid == ResourceId())
     return (WrappedResourceType)RecordType::NullResource;
 
-  RDCASSERT(HasLiveResource(origid), origid);
+#if DISABLED(RDOC_RELEASE)
+  if(!optional)
+  {
+    RDCASSERT(HasLiveResource(origid), origid);
+  }
+#endif
 
-  if(m_Replacements.find(origid) != m_Replacements.end())
-    return GetLiveResource(m_Replacements[origid]);
+  {
+    auto it = m_Replacements.find(origid);
+    if(it != m_Replacements.end())
+      return GetLiveResource(it->second);
+  }
 
-  if(m_LiveResourceMap.find(origid) != m_LiveResourceMap.end())
-    return m_LiveResourceMap[origid];
+  {
+    auto it = m_LiveResourceMap.find(origid);
+    if(it != m_LiveResourceMap.end())
+      return it->second;
+  }
 
   return (WrappedResourceType)RecordType::NullResource;
 }

renderdoc/driver/d3d12/d3d12_manager.cpp

@@ -629,10 +629,8 @@ D3D12Descriptor *DescriptorFromPortableHandle(D3D12ResourceManager *manager, Por
   if(handle.heap == ResourceId())
     return NULL;
 
-  if(!manager->HasLiveResource(handle.heap))
-    return NULL;
-
-  WrappedID3D12DescriptorHeap *heap = manager->GetLiveAs<WrappedID3D12DescriptorHeap>(handle.heap);
+  WrappedID3D12DescriptorHeap *heap =
+      manager->GetLiveAs<WrappedID3D12DescriptorHeap>(handle.heap, true);
 
   if(heap)
     return heap->GetDescriptors() + handle.index;

renderdoc/driver/d3d12/d3d12_manager.h

@@ -693,9 +693,9 @@ public:
   {
   }
   template <class T>
-  T *GetLiveAs(ResourceId id)
+  T *GetLiveAs(ResourceId id, bool optional = false)
   {
-    return (T *)GetLiveResource(id);
+    return (T *)GetLiveResource(id, optional);
   }
 
   template <class T>