[AddressLowering] Handle weak copies.

Lower the `strong_copy_weak_value` and `weak_copy_value` to `load_weak`
and `store_weak` respectively.

Author: nate-chandler

lib/SILOptimizer/Mandatory/AddressLowering.cpp

@@ -3483,6 +3483,14 @@ class UseRewriter : SILInstructionVisitor<UseRewriter> {
     pass.deleter.forceDelete(sei);
   }
 
+  void visitStrongCopyWeakValueInst(StrongCopyWeakValueInst *scwvi) {
+    auto sourceAddr = addrMat.materializeAddress(use->get());
+    SILValue value =
+        builder.createLoadWeak(scwvi->getLoc(), sourceAddr, IsNotTake);
+    scwvi->replaceAllUsesWith(value);
+    pass.deleter.forceDelete(scwvi);
+  }
+
   // Extract from an opaque struct.
   void visitStructExtractInst(StructExtractInst *extractInst);
 
@@ -4094,6 +4102,15 @@ class DefRewriter : SILInstructionVisitor<DefRewriter> {
 
     rewriteUnconditionalCheckedCastInst(uncondCheckedCast, pass);
   }
+
+  void visitWeakCopyValueInst(WeakCopyValueInst *wcsvi) {
+    auto &storage = pass.valueStorageMap.getStorage(wcsvi);
+    auto destAddr = addrMat.recursivelyMaterializeStorage(
+        storage, /*intoPhiOperand=*/false);
+
+    builder.createStoreWeak(wcsvi->getLoc(), wcsvi->getOperand(), destAddr,
+                            IsInitialization);
+  }
 };
 } // end anonymous namespace
 

test/SILOptimizer/address_lowering_lib.sil

@@ -1,4 +1,4 @@
-// RUN: %target-sil-opt -address-lowering -enable-sil-opaque-values -sil-verify-all %s | %FileCheck %s
+// RUN: %target-sil-opt -address-lowering -emit-sorted-sil -enable-sil-opaque-values -sil-verify-all %s | %FileCheck %s
 //
 import Builtin
 import Swift
@@ -29,3 +29,34 @@ bb0(%0 : @owned $Error):
   %ret = tuple ()
   return %ret : $()
 }
+
+struct WeakBox<T : AnyObject> {
+  weak var t: T?
+}
+
+// CHECK-LABEL: sil [ossa] @test_strong_copy_weak_value : {{.*}} {
+// CHECK:       {{bb[0-9]+}}([[BOX_ADDR:%[^,]+]] :
+// CHECK:         [[VALUE_ADDR:%[^,]+]] = struct_element_addr [[BOX_ADDR]] : {{.*}}, #WeakBox.t
+// CHECK:         [[VALUE:%[^,]+]] = load_weak [[VALUE_ADDR]] : $*@sil_weak Optional<T>
+// CHECK:         return [[VALUE]] : $Optional<T>
+// CHECK-LABEL: } // end sil function 'test_strong_copy_weak_value'
+sil [ossa] @test_strong_copy_weak_value : $@convention(thin) <T where T : AnyObject> (@in_guaranteed WeakBox<T>) -> @owned Optional<T> {
+bb0(%instance : @guaranteed $WeakBox<T>):
+  %weak_optional = struct_extract %instance : $WeakBox<T>, #WeakBox.t
+  %strong_optional = strong_copy_weak_value %weak_optional : $@sil_weak Optional<T>
+  return %strong_optional : $Optional<T>
+}
+
+// CHECK-LABEL: sil [ossa] @test_weak_copy_value_1 : {{.*}} {
+// CHECK:       {{bb[0-9]+}}([[RETVAL:%[^,]+]] : $*WeakBox<T>, [[VALUE:%[^,]+]] :
+// CHECK:         [[VALUE_ADDR:%[^,]+]] = struct_element_addr [[RETVAL]] : {{.*}}, #WeakBox.t
+// CHECK:         store_weak [[VALUE]] to [init] [[VALUE_ADDR]]
+// CHECK:         destroy_value [[VALUE]]
+// CHECK-LABEL: } // end sil function 'test_weak_copy_value_1'
+sil [ossa] @test_weak_copy_value_1 : $@convention(thin) <T where T : AnyObject> (@owned Optional<T>) -> @out WeakBox<T> {
+bb0(%value : @owned $Optional<T>):
+  %weak_value = weak_copy_value %value : $Optional<T>
+  destroy_value %value : $Optional<T>
+  %retval = struct $WeakBox<T> (%weak_value : $@sil_weak Optional<T>)
+  return %retval : $WeakBox<T>
+}