diff --git a/Engine/Source/Editor/UnrealEd/Public/Layers/LayersSubsystem.h b/Engine/Source/Editor/UnrealEd/Public/Layers/LayersSubsystem.h
index 7fbded01fbb..80e507524f7 100644
--- a/Engine/Source/Editor/UnrealEd/Public/Layers/LayersSubsystem.h
+++ b/Engine/Source/Editor/UnrealEd/Public/Layers/LayersSubsystem.h
@@ -41,7 +41,7 @@ namespace ELayersAction
 }
 
 UCLASS()
-class UNREALED_API ULayersSubsystem : public UEditorSubsystem
+class UNREALED_API ULayersSubsystem final : public UEditorSubsystem
 {
 	GENERATED_BODY()
 
diff --git a/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/LinuxToolChain.cs b/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/LinuxToolChain.cs
index 1f856d789be..b4ffbeb2950 100644
--- a/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/LinuxToolChain.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/LinuxToolChain.cs
@@ -186,10 +186,10 @@ namespace UnrealBuildTool
 				throw new BuildException("Unable to build: no compatible clang version found. Please run Setup.sh");
 			}
 			// prevent unknown clangs since the build is likely to fail on too old or too new compilers
-			else if ((CompilerVersionMajor * 10 + CompilerVersionMinor) > 100 || (CompilerVersionMajor * 10 + CompilerVersionMinor) < 60)
+			else if ((CompilerVersionMajor * 10 + CompilerVersionMinor) > 111 || (CompilerVersionMajor * 10 + CompilerVersionMinor) < 60)
 			{
 				throw new BuildException(
-					string.Format("This version of the Unreal Engine can only be compiled with clang 10.0, 9.0, 8.0, 7.0 and 6.0. clang {0} may not build it - please use a different version.",
+					string.Format("This version of the Unreal Engine can only be compiled with clang 11.1, 10.0, 9.0, 8.0, 7.0 and 6.0. clang {0} may not build it - please use a different version.",
 						CompilerVersionString)
 					);
 			}
@@ -592,6 +592,12 @@ namespace UnrealBuildTool
 			}
 
 			Result += " -Wall -Werror";
+			
+			if(CompilerVersionGreaterOrEqual(11,0,0))
+			{
+				//instantiate templates once and reuse at compilation. Approximately 30% faster compile times
+				Result += " -fpch-instantiate-templates";
+			}
 
 			if (!CompileEnvironment.Architecture.StartsWith("x86_64") && !CompileEnvironment.Architecture.StartsWith("i686"))
 			{
diff --git a/Engine/Source/Runtime/Core/Public/GenericPlatform/GenericPlatformCriticalSection.h b/Engine/Source/Runtime/Core/Public/GenericPlatform/GenericPlatformCriticalSection.h
index 82dbd7f0c21..639a7cdcca7 100644
--- a/Engine/Source/Runtime/Core/Public/GenericPlatform/GenericPlatformCriticalSection.h
+++ b/Engine/Source/Runtime/Core/Public/GenericPlatform/GenericPlatformCriticalSection.h
@@ -39,6 +39,7 @@ template<class CriticalSection>
 class TGenericPlatformRWLock
 {
 public:
+	
 	FORCEINLINE TGenericPlatformRWLock()
 	{
 	}
diff --git a/Engine/Source/Runtime/Core/Public/HAL/PThreadCriticalSection.h b/Engine/Source/Runtime/Core/Public/HAL/PThreadCriticalSection.h
index ff9c2e10bb5..3f547f1ea0b 100644
--- a/Engine/Source/Runtime/Core/Public/HAL/PThreadCriticalSection.h
+++ b/Engine/Source/Runtime/Core/Public/HAL/PThreadCriticalSection.h
@@ -66,6 +66,11 @@ public:
 	{
 		pthread_mutex_unlock(&Mutex);
 	}
+	
+	FORCEINLINE pthread_mutex_t GetMutex() const
+	{
+		return this->Mutex;
+	}
 
 private:
 	FPThreadsCriticalSection(const FPThreadsCriticalSection&);
diff --git a/Engine/Source/Runtime/Core/Public/UObject/WeakObjectPtrTemplates.h b/Engine/Source/Runtime/Core/Public/UObject/WeakObjectPtrTemplates.h
index f2d367b57bd..771c337a209 100644
--- a/Engine/Source/Runtime/Core/Public/UObject/WeakObjectPtrTemplates.h
+++ b/Engine/Source/Runtime/Core/Public/UObject/WeakObjectPtrTemplates.h
@@ -382,4 +382,4 @@ void CopyFromWeakArray(DestArrayType& Dest, const SourceArrayType& Src)
 			Dest.Add(Value);
 		}
 	}
-}
\ No newline at end of file
+}
diff --git a/Engine/Source/Runtime/Foliage/Private/ProceduralFoliageSpawner.cpp b/Engine/Source/Runtime/Foliage/Private/ProceduralFoliageSpawner.cpp
index d6ffcf228cf..04e2ef2a316 100644
--- a/Engine/Source/Runtime/Foliage/Private/ProceduralFoliageSpawner.cpp
+++ b/Engine/Source/Runtime/Foliage/Private/ProceduralFoliageSpawner.cpp
@@ -80,7 +80,7 @@ const UProceduralFoliageTile* UProceduralFoliageSpawner::GetRandomTile(int32 X,
 		HashStream.Initialize(Y);
 		const double YRand = HashStream.FRand();
 		
-		const int32 RandomNumber = (RAND_MAX * XRand / (YRand + 0.01));
+		const int32 RandomNumber = (static_cast<double>(RAND_MAX) * XRand / (YRand + 0.01));
 		const int32 Idx = FMath::Clamp(RandomNumber % PrecomputedTiles.Num(), 0, PrecomputedTiles.Num() - 1);
 		return PrecomputedTiles[Idx].Get();
 	}
diff --git a/Engine/Source/ThirdParty/FBX/2020.1.1/include/fbxsdk/scene/geometry/fbxlayer.h b/Engine/Source/ThirdParty/FBX/2020.1.1/include/fbxsdk/scene/geometry/fbxlayer.h
index 42d703fb8a8..1619c09c79b 100644
--- a/Engine/Source/ThirdParty/FBX/2020.1.1/include/fbxsdk/scene/geometry/fbxlayer.h
+++ b/Engine/Source/ThirdParty/FBX/2020.1.1/include/fbxsdk/scene/geometry/fbxlayer.h
@@ -461,7 +461,7 @@ public:
       *	                                 deleted when the pointer is released or the object is destroyed. At the moment of 
       *                                  release or destruction, the values in this buffer are copied back into this object.
 	  */
-	template <class T> inline T* GetLocked(T*, ELockMode pLockMode=eReadWriteLock) {T v; return (T*)GetLocked(pLockMode, FbxTypeOf(v)); }
+	template <class T> inline T* GetLocked(T*, ELockMode pLockMode=eReadWriteLock) {T v = T(); return (T*)GetLocked(pLockMode, FbxTypeOf(v)); }
 
 	/** Unlock the data buffer.
 	  * \param pDataPtr                  The buffer to be released.