LoadableByAddress: Must be able to materialize undef operands

rdar://145092298

Author: aschwaighofer

lib/IRGen/LoadableByAddress.cpp

@@ -1883,7 +1883,14 @@ void LoadableStorageAllocation::replaceLoad(LoadInst *load) {
 
 static void allocateAndSet(StructLoweringState &pass,
                            LoadableStorageAllocation &allocator,
-                           SILValue operand, SILInstruction *user) {
+                           SILValue operand, SILInstruction *user,
+                           Operand &opd) {
+  if (isa<SILUndef>(operand)) {
+    auto alloc = allocate(pass, operand->getType());
+    opd.set(alloc);
+    return;
+  }
+
   auto inst = operand->getDefiningInstruction();
   if (!inst) {
     allocateAndSetForArgument(pass, cast<SILArgument>(operand), user);