Revert "Simplify lifetime extension for async ObjC calls."

This reverts commit 01d470c.

Just to be safe, I'm reverting this part of #41571
as well, until it can be reimplemented in light of issues where a hop
can appear between a get_continuation and an await_continuation

resolves rdar://91502776

Author: kavon

lib/SILGen/ManagedValue.cpp

@@ -58,20 +58,20 @@ ManagedValue ManagedValue::copy(SILGenFunction &SGF, SILLocation loc) const {
 
 // Emit an unmanaged copy of this value
 // WARNING: Callers of this API should manage the cleanup of this value!
-SILValue ManagedValue::unmanagedCopy(SILGenFunction &SGF,
+ManagedValue ManagedValue::unmanagedCopy(SILGenFunction &SGF,
                                          SILLocation loc) const {
   auto &lowering = SGF.getTypeLowering(getType());
   if (lowering.isTrivial())
-    return getValue();
+    return *this;
 
   if (getType().isObject()) {
     auto copy = SGF.B.emitCopyValueOperation(loc, getValue());
-    return copy;
+    return ManagedValue::forUnmanaged(copy);
   }
 
   SILValue buf = SGF.emitTemporaryAllocation(loc, getType());
   SGF.B.createCopyAddr(loc, getValue(), buf, IsNotTake, IsInitialization);
-  return buf;
+  return ManagedValue::forUnmanaged(buf);
 }
 
 /// Emit a copy of this value with independent ownership.

lib/SILGen/ManagedValue.h

@@ -280,7 +280,7 @@ class ManagedValue {
 
   /// Returns an unmanaged copy of this value.
   /// WARNING: Callers of this API should manage the cleanup of this value!
-  SILValue unmanagedCopy(SILGenFunction &SGF, SILLocation loc) const;
+  ManagedValue unmanagedCopy(SILGenFunction &SGF, SILLocation loc) const;
 
   /// Emit a copy of this value with independent ownership into the current
   /// formal evaluation scope.

lib/SILGen/SILGenApply.cpp

@@ -4586,7 +4586,7 @@ RValue SILGenFunction::emitApply(
   // generates `await_async_continuation`.
   // Lifetime is extended by creating unmanaged copies here and by pushing the
   // cleanups required just before the result plan is generated.
-  SmallVector<SILValue, 8> unmanagedCopies;
+  SmallVector<ManagedValue, 8> unmanagedCopies;
   if (calleeTypeInfo.foreign.async) {
     for (auto arg : args) {
       if (arg.hasCleanup()) {
@@ -4673,22 +4673,29 @@ RValue SILGenFunction::emitApply(
                               *foreignError, calleeTypeInfo.foreign.async);
   }
 
-  // For objc async calls, push cleanup to be used on
-  // both result and throw paths prior to finishing the result plan.
-  if (calleeTypeInfo.foreign.async) {
-    for (auto unmanagedCopy : unmanagedCopies) {
-      Cleanups.pushCleanup<FixLifetimeDestroyCleanup>(unmanagedCopy);
-    }
-  } else {
-    assert(unmanagedCopies.empty());
+  // For objc async calls, push cleanup to be used on throw paths in the result
+  // planner.
+  for (unsigned i : indices(unmanagedCopies)) {
+    SILValue value = unmanagedCopies[i].getValue();
+    Cleanups.pushCleanup<FixLifetimeDestroyCleanup>(value);
+    unmanagedCopies[i] = ManagedValue(value, Cleanups.getTopCleanup());
   }
 
   auto directResultsArray = makeArrayRef(directResults);
   RValue result = resultPlan->finish(*this, loc, substResultType,
                                      directResultsArray, bridgedForeignError);
   assert(directResultsArray.empty() && "didn't claim all direct results");
 
+  // For objc async calls, generate cleanup on the resume path here and forward
+  // the previously pushed cleanups.
   if (calleeTypeInfo.foreign.async) {
+    for (auto unmanagedCopy : unmanagedCopies) {
+      auto value = unmanagedCopy.forward(*this);
+      B.emitFixLifetime(loc, value);
+      B.emitDestroyOperation(loc, value);
+    }
+
+    // hop back to the current executor
     breadcrumb.emit(*this, loc);
   }
 

test/SILGen/objc_async.swift

@@ -195,9 +195,9 @@ func testSlowServerFromMain(slowServer: SlowServer) async throws {
   // CHECK: await_async_continuation [[CONT]] {{.*}}, resume [[RESUME:bb[0-9]+]]
   // CHECK: [[RESUME]]:
   // CHECK: [[RESULT:%.*]] = load [trivial] [[RESUME_BUF]]
-  // CHECK: hop_to_executor %6 : $MainActor
   // CHECK: fix_lifetime [[COPY]]
   // CHECK: destroy_value [[COPY]]
+  // CHECK: hop_to_executor %6 : $MainActor
   // CHECK: dealloc_stack [[RESUME_BUF]]
   let _: Int = await slowServer.doSomethingSlow("mail")
 }