[SIL Opaque Value] Fix SILGen to not generate store_borrow for +0 opaque values (#42488)

Author: meg-gupta

lib/SILGen/ManagedValue.cpp

@@ -206,13 +206,21 @@ ManagedValue ManagedValue::materialize(SILGenFunction &SGF,
                                   StoreOwnershipQualifier::Init);
 
     // SEMANTIC SIL TODO: This should really be called a temporary LValue.
-    return ManagedValue::forOwnedAddressRValue(temporary,
-                                          SGF.enterDestroyCleanup(temporary));
-  } else {
-    auto object = SGF.emitManagedBeginBorrow(loc, getValue());
-    SGF.emitManagedStoreBorrow(loc, object.getValue(), temporary);
-    return ManagedValue::forBorrowedAddressRValue(temporary);
+    return ManagedValue::forOwnedAddressRValue(
+        temporary, SGF.enterDestroyCleanup(temporary));
+  }
+  auto &lowering = SGF.getTypeLowering(getType());
+  if (lowering.isAddressOnly()) {
+    assert(!SGF.silConv.useLoweredAddresses());
+    auto copy = SGF.B.createCopyValue(loc, getValue());
+    SGF.B.emitStoreValueOperation(loc, copy, temporary,
+                                  StoreOwnershipQualifier::Init);
+    return ManagedValue::forOwnedAddressRValue(
+        temporary, SGF.enterDestroyCleanup(temporary));
   }
+  auto object = SGF.emitManagedBeginBorrow(loc, getValue());
+  SGF.emitManagedStoreBorrow(loc, object.getValue(), temporary);
+  return ManagedValue::forBorrowedAddressRValue(temporary);
 }
 
 void ManagedValue::print(raw_ostream &os) const {

test/SILGen/opaque_values_silgen.swift

@@ -62,12 +62,14 @@ func forEachStmt() {
 // ---
 // CHECK-LABEL: sil hidden [ossa] @$s20opaque_values_silgen12openExistBoxySSs5Error_pF : $@convention(thin) (@guaranteed Error) -> @owned String {
 // CHECK: bb0([[ARG:%.*]] : @guaranteed $Error):
-// HECK:   [[OPAQUE_ARG:%.*]] = open_existential_box_value [[ARG]] : $Error to $@opened({{.*}}) Error
-// HECK:   [[ALLOC_OPEN:%.*]] = alloc_stack $@opened({{.*}}) Error
-// HECK:   store_borrow [[OPAQUE_ARG]] to [[ALLOC_OPEN]]
-// HECK:   dealloc_stack [[ALLOC_OPEN]]
+// CHECK:   [[OPAQUE_ARG:%.*]] = open_existential_box_value [[ARG]] : $Error to $@opened({{.*}}) Error
+// CHECK:   [[ALLOC_OPEN:%.*]] = alloc_stack $@opened({{.*}}) Error
+// CHECK:   [[COPY:%.*]] = copy_value [[OPAQUE_ARG]]
+// CHECK:   store [[COPY]] to [init] [[ALLOC_OPEN]]
+// CHECK:   destroy_addr [[ALLOC_OPEN]]
+// CHECK:   dealloc_stack [[ALLOC_OPEN]]
 // CHECK-NOT:   destroy_value [[ARG]] : $Error
-// HECK:   return {{.*}} : $String
+// CHECK:   return {{.*}} : $String
 // CHECK-LABEL: } // end sil function '$s20opaque_values_silgen12openExistBoxySSs5Error_pF'
 func openExistBox(_ x: Error) -> String {
   return x._domain