diff --git a/src/Pipeline/SpirvShader.cpp b/src/Pipeline/SpirvShader.cpp
index cf46147..75fe463 100644
--- a/src/Pipeline/SpirvShader.cpp
+++ b/src/Pipeline/SpirvShader.cpp
@@ -331,9 +331,9 @@
 				}
 				if (ptr.hasStaticSequentialOffsets(sizeof(float)))
 				{
-					return rr::MaskedLoad(rr::Pointer<T>(ptr.base + ptr.staticOffsets[0]), mask, alignment);
+					return rr::MaskedLoad(rr::Pointer<T>(ptr.base + ptr.staticOffsets[0]), mask, alignment, robust);
 				}
-				return rr::Gather(rr::Pointer<EL>(ptr.base), offsets, mask, alignment);
+				return rr::Gather(rr::Pointer<EL>(ptr.base), offsets, mask, alignment, robust);
 			}
 			else
 			{
diff --git a/src/Reactor/LLVMReactor.cpp b/src/Reactor/LLVMReactor.cpp
index af049c6..8d08ca4 100644
--- a/src/Reactor/LLVMReactor.cpp
+++ b/src/Reactor/LLVMReactor.cpp
@@ -1596,7 +1596,7 @@
 		}
 	}
 
-	Value *Nucleus::createMaskedLoad(Value *ptr, Type *elTy, Value *mask, unsigned int alignment)
+	Value *Nucleus::createMaskedLoad(Value *ptr, Type *elTy, Value *mask, unsigned int alignment, bool zeroMaskedLanes)
 	{
 		ASSERT(V(ptr)->getType()->isPointerTy());
 		ASSERT(V(mask)->getType()->isVectorTy());
@@ -1607,7 +1607,7 @@
 		auto elVecTy = ::llvm::VectorType::get(T(elTy), numEls);
 		auto elVecPtrTy = elVecTy->getPointerTo();
 		auto i8Mask = jit->builder->CreateIntCast(V(mask), ::llvm::VectorType::get(i1Ty, numEls), false); // vec<int, int, ...> -> vec<bool, bool, ...>
-		auto passthrough = ::llvm::Constant::getNullValue(elVecTy);
+		auto passthrough = zeroMaskedLanes ? ::llvm::Constant::getNullValue(elVecTy) : llvm::UndefValue::get(elVecTy);
 		auto align = ::llvm::ConstantInt::get(i32Ty, alignment);
 		auto func = ::llvm::Intrinsic::getDeclaration(jit->module.get(), llvm::Intrinsic::masked_load, { elVecTy, elVecPtrTy } );
 		return V(jit->builder->CreateCall(func, { V(ptr), align, i8Mask, passthrough }));
@@ -1630,7 +1630,7 @@
 		jit->builder->CreateCall(func, { V(val), V(ptr), align, i8Mask });
 	}
 
-	Value *Nucleus::createGather(Value *base, Type *elTy, Value *offsets, Value *mask, unsigned int alignment)
+	Value *Nucleus::createGather(Value *base, Type *elTy, Value *offsets, Value *mask, unsigned int alignment, bool zeroMaskedLanes)
 	{
 		ASSERT(V(base)->getType()->isPointerTy());
 		ASSERT(V(offsets)->getType()->isVectorTy());
@@ -1648,7 +1648,7 @@
 		auto i8Ptrs = jit->builder->CreateGEP(i8Base, V(offsets));
 		auto elPtrs = jit->builder->CreatePointerCast(i8Ptrs, elPtrVecTy);
 		auto i8Mask = jit->builder->CreateIntCast(V(mask), ::llvm::VectorType::get(i1Ty, numEls), false); // vec<int, int, ...> -> vec<bool, bool, ...>
-		auto passthrough = ::llvm::Constant::getNullValue(elVecTy);
+		auto passthrough = zeroMaskedLanes ? ::llvm::Constant::getNullValue(elVecTy) : llvm::UndefValue::get(elVecTy);
 		auto align = ::llvm::ConstantInt::get(i32Ty, alignment);
 		auto func = ::llvm::Intrinsic::getDeclaration(jit->module.get(), llvm::Intrinsic::masked_gather, { elVecTy, elPtrVecTy } );
 		return V(jit->builder->CreateCall(func, { elPtrs, align, i8Mask, passthrough }));
diff --git a/src/Reactor/Nucleus.hpp b/src/Reactor/Nucleus.hpp
index 1b4e2db..819d100 100644
--- a/src/Reactor/Nucleus.hpp
+++ b/src/Reactor/Nucleus.hpp
@@ -133,11 +133,11 @@
 		static Value *createGEP(Value *ptr, Type *type, Value *index, bool unsignedIndex);
 
 		// Masked Load / Store instructions
-		static Value *createMaskedLoad(Value *base, Type *elementType, Value *mask, unsigned int alignment);
+		static Value *createMaskedLoad(Value *base, Type *elementType, Value *mask, unsigned int alignment, bool zeroMaskedLanes);
 		static void createMaskedStore(Value *base, Value *value, Value *mask, unsigned int alignment);
 
 		// Scatter / Gather instructions
-		static Value *createGather(Value *base, Type *elementType, Value *offsets, Value *mask, unsigned int alignment);
+		static Value *createGather(Value *base, Type *elementType, Value *offsets, Value *mask, unsigned int alignment, bool zeroMaskedLanes);
 		static void createScatter(Value *base, Value *value, Value *offsets, Value *mask, unsigned int alignment);
 
 		// Barrier instructions
diff --git a/src/Reactor/Reactor.cpp b/src/Reactor/Reactor.cpp
index de39d4a..bb94cf5 100644
--- a/src/Reactor/Reactor.cpp
+++ b/src/Reactor/Reactor.cpp
@@ -4232,14 +4232,14 @@
 		Nucleus::setInsertBlock(bodyBB);
 	}
 
-	RValue<Float4> MaskedLoad(RValue<Pointer<Float4>> base, RValue<Int4> mask, unsigned int alignment)
+	RValue<Float4> MaskedLoad(RValue<Pointer<Float4>> base, RValue<Int4> mask, unsigned int alignment, bool zeroMaskedLanes /* = false */)
 	{
-		return RValue<Float4>(Nucleus::createMaskedLoad(base.value, Float::getType(), mask.value, alignment));
+		return RValue<Float4>(Nucleus::createMaskedLoad(base.value, Float::getType(), mask.value, alignment, zeroMaskedLanes));
 	}
 
-	RValue<Int4> MaskedLoad(RValue<Pointer<Int4>> base, RValue<Int4> mask, unsigned int alignment)
+	RValue<Int4> MaskedLoad(RValue<Pointer<Int4>> base, RValue<Int4> mask, unsigned int alignment, bool zeroMaskedLanes /* = false */)
 	{
-		return RValue<Int4>(Nucleus::createMaskedLoad(base.value, Int::getType(), mask.value, alignment));
+		return RValue<Int4>(Nucleus::createMaskedLoad(base.value, Int::getType(), mask.value, alignment, zeroMaskedLanes));
 	}
 
 	void MaskedStore(RValue<Pointer<Float4>> base, RValue<Float4> val, RValue<Int4> mask, unsigned int alignment)
@@ -4252,14 +4252,14 @@
 		Nucleus::createMaskedStore(base.value, val.value, mask.value, alignment);
 	}
 
-	RValue<Float4> Gather(RValue<Pointer<Float>> base, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment)
+	RValue<Float4> Gather(RValue<Pointer<Float>> base, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment, bool zeroMaskedLanes /* = false */)
 	{
-		return RValue<Float4>(Nucleus::createGather(base.value, Float::getType(), offsets.value, mask.value, alignment));
+		return RValue<Float4>(Nucleus::createGather(base.value, Float::getType(), offsets.value, mask.value, alignment, zeroMaskedLanes));
 	}
 
-	RValue<Int4> Gather(RValue<Pointer<Int>> base, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment)
+	RValue<Int4> Gather(RValue<Pointer<Int>> base, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment, bool zeroMaskedLanes /* = false */)
 	{
-		return RValue<Int4>(Nucleus::createGather(base.value, Int::getType(), offsets.value, mask.value, alignment));
+		return RValue<Int4>(Nucleus::createGather(base.value, Int::getType(), offsets.value, mask.value, alignment, zeroMaskedLanes));
 	}
 
 	void Scatter(RValue<Pointer<Float>> base, RValue<Float4> val, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment)
diff --git a/src/Reactor/Reactor.hpp b/src/Reactor/Reactor.hpp
index 53853c0..1391275 100644
--- a/src/Reactor/Reactor.hpp
+++ b/src/Reactor/Reactor.hpp
@@ -2369,13 +2369,13 @@
 	}
 
 	// TODO: Use SIMD to template these.
-	RValue<Float4> MaskedLoad(RValue<Pointer<Float4>> base, RValue<Int4> mask, unsigned int alignment);
-	RValue<Int4> MaskedLoad(RValue<Pointer<Int4>> base, RValue<Int4> mask, unsigned int alignment);
+	RValue<Float4> MaskedLoad(RValue<Pointer<Float4>> base, RValue<Int4> mask, unsigned int alignment, bool zeroMaskedLanes = false);
+	RValue<Int4> MaskedLoad(RValue<Pointer<Int4>> base, RValue<Int4> mask, unsigned int alignment, bool zeroMaskedLanes = false);
 	void MaskedStore(RValue<Pointer<Float4>> base, RValue<Float4> val, RValue<Int4> mask, unsigned int alignment);
 	void MaskedStore(RValue<Pointer<Int4>> base, RValue<Int4> val, RValue<Int4> mask, unsigned int alignment);
 
-	RValue<Float4> Gather(RValue<Pointer<Float>> base, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment);
-	RValue<Int4> Gather(RValue<Pointer<Int>> base, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment);
+	RValue<Float4> Gather(RValue<Pointer<Float>> base, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment, bool zeroMaskedLanes = false);
+	RValue<Int4> Gather(RValue<Pointer<Int>> base, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment, bool zeroMaskedLanes = false);
 	void Scatter(RValue<Pointer<Float>> base, RValue<Float4> val, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment);
 	void Scatter(RValue<Pointer<Int>> base, RValue<Int4> val, RValue<Int4> offsets, RValue<Int4> mask, unsigned int alignment);
 
diff --git a/src/Reactor/SubzeroReactor.cpp b/src/Reactor/SubzeroReactor.cpp
index e8cc581..bcc2f7e 100644
--- a/src/Reactor/SubzeroReactor.cpp
+++ b/src/Reactor/SubzeroReactor.cpp
@@ -3476,9 +3476,9 @@
 	// Below are functions currently unimplemented for the Subzero backend.
 	// They are stubbed to satisfy the linker.
 	void Nucleus::createFence(std::memory_order memoryOrder) { UNIMPLEMENTED("Subzero createFence()"); }
-	Value *Nucleus::createMaskedLoad(Value *ptr, Type *elTy, Value *mask, unsigned int alignment) { UNIMPLEMENTED("Subzero createMaskedLoad()"); return nullptr; }
+	Value *Nucleus::createMaskedLoad(Value *ptr, Type *elTy, Value *mask, unsigned int alignment, bool zeroMaskedLanes) { UNIMPLEMENTED("Subzero createMaskedLoad()"); return nullptr; }
 	void Nucleus::createMaskedStore(Value *ptr, Value *val, Value *mask, unsigned int alignment) { UNIMPLEMENTED("Subzero createMaskedStore()"); }
-	Value *Nucleus::createGather(Value *base, Type *elTy, Value *offsets, Value *mask, unsigned int alignment) { UNIMPLEMENTED("Subzero createGather()"); return nullptr; }
+	Value *Nucleus::createGather(Value *base, Type *elTy, Value *offsets, Value *mask, unsigned int alignment, bool zeroMaskedLanes) { UNIMPLEMENTED("Subzero createGather()"); return nullptr; }
 	void Nucleus::createScatter(Value *base, Value *val, Value *offsets, Value *mask, unsigned int alignment) { UNIMPLEMENTED("Subzero createScatter()"); }
 	RValue<Float4> Sin(RValue<Float4> x) { UNIMPLEMENTED("Subzero Sin()"); return Float4(0); }
 	RValue<Float4> Cos(RValue<Float4> x) { UNIMPLEMENTED("Subzero Cos()"); return Float4(0); }