Index: lib/Target/WebAssembly/WebAssemblyISelLowering.h
===================================================================
--- lib/Target/WebAssembly/WebAssemblyISelLowering.h
+++ lib/Target/WebAssembly/WebAssemblyISelLowering.h
@@ -64,6 +64,13 @@
   bool allowsMisalignedMemoryAccesses(EVT, unsigned AddrSpace, unsigned Align,
                                       bool *Fast) const override;
   bool isIntDivCheap(EVT VT, AttributeList Attr) const override;
+  bool
+  shouldExpandBuildVectorWithShuffles(EVT,
+                                      unsigned DefinedValues) const override;
+  bool storeOfVectorConstantIsCheap(EVT MemVT, unsigned NumElem,
+                                    unsigned AddrSpace) const override;
+  bool shouldSplatInsEltVarIndex(EVT) const override;
+  bool isVectorShiftByScalarCheap(Type *Ty) const override;
 
   EVT getSetCCResultType(const DataLayout &DL, LLVMContext &Context,
                          EVT VT) const override;
Index: lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
===================================================================
--- lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -508,6 +508,28 @@
   return true;
 }
 
+bool WebAssemblyTargetLowering::shouldExpandBuildVectorWithShuffles(
+    EVT, unsigned DefinedValues) const {
+  // Shuffles are very large (18 bytes!), so we would rather not use them.
+  return false;
+}
+
+bool WebAssemblyTargetLowering::storeOfVectorConstantIsCheap(
+    EVT MemVT, unsigned NumElem, unsigned AddrSpace) const {
+  // The alternative is to store each element individually, which is more code.
+  return true;
+}
+
+bool WebAssemblyTargetLowering::shouldSplatInsEltVarIndex(EVT) const {
+  // WebAssembly has native splats.
+  return true;
+}
+
+bool WebAssemblyTargetLowering::isVectorShiftByScalarCheap(Type *Ty) const {
+  // Anything else is actually very expensive.
+  return true;
+}
+
 EVT WebAssemblyTargetLowering::getSetCCResultType(const DataLayout &DL,
                                                   LLVMContext &C,
                                                   EVT VT) const {