[MOWTE] Visit undef values.

Such values' types may also also be move-only wrapped.

Author: nate-chandler

lib/SILOptimizer/Mandatory/MoveOnlyWrappedTypeEliminator.cpp

@@ -307,7 +307,11 @@ bool SILMoveOnlyWrappedTypeEliminator::process() {
     for (auto *use : value->getNonTypeDependentUses())
       touchedInsts.insert(use->getUser());
 
-    value->unsafelyEliminateMoveOnlyWrapper(fn);
+    if (isa<SILUndef>(value))
+      value->replaceAllUsesWith(
+          SILUndef::get(fn, value->getType().removingAnyMoveOnlyWrapping(fn)));
+    else
+      value->unsafelyEliminateMoveOnlyWrapper(fn);
 
     return true;
   };
@@ -342,6 +346,16 @@ bool SILMoveOnlyWrappedTypeEliminator::process() {
       madeChange = true;
     }
   }
+  // SILFunction::undefValues may grow during the loop.
+  SmallVector<std::pair<SILType, SILUndef *>, 4> originalUndefs(
+      fn->getUndefValues());
+  for (auto pair : originalUndefs) {
+    bool relevant = visitValue(pair.second);
+    if (!relevant)
+      continue;
+
+    madeChange = true;
+  }
 
   SILMoveOnlyWrappedTypeEliminatorVisitor visitor;
   while (!touchedInsts.empty()) {

test/SILOptimizer/moveonly_type_eliminator.sil

@@ -562,3 +562,19 @@ bb3(%result : @owned $@moveOnly FakeOptional<Klass>):
   %result2 = moveonlywrapper_to_copyable [owned] %result : $@moveOnly FakeOptional<Klass>
   return %result2 : $FakeOptional<Klass>
 }
+
+// CHECK-LABEL: sil [ossa] @debug_value_undef : {{.*}} {
+// CHECK:         debug_value [moveable_value_debuginfo] undef : $*Klass, var, name "s"
+// CHECK-LABEL: } // end sil function 'debug_value_undef'
+sil  [ossa] @debug_value_undef : $@convention(thin) (@owned Klass) -> () {
+bb0(%x : @owned $Klass):
+  %addr = alloc_stack $@moveOnly Klass
+  %unwrapped_addr = moveonlywrapper_to_copyable_addr %addr : $*@moveOnly Klass
+  store %x to [init] %unwrapped_addr : $*Klass
+  debug_value %addr : $*@moveOnly Klass, var, name "s", argno 1, expr op_deref
+  destroy_addr %addr : $*@moveOnly Klass
+  debug_value undef : $*@moveOnly Klass, var, name "s", argno 1, expr op_deref
+  dealloc_stack %addr : $*@moveOnly Klass
+  %retval = tuple ()
+  return %retval : $()
+}