DI: Track of initialization state of trivial fields in root class initializers

While we don't need to destroy these fields, we still need to know
when the class is _semantically_ fully initialized, since this will
determine if we're going to release the class, running the deinitializer,
or if we're going to deallocate the memory for the instance directly.

Author: slavapestov

lib/SILOptimizer/Mandatory/DIMemoryUseCollector.h

@@ -176,6 +176,11 @@ class DIMemoryObjectInfo {
            MemoryInst->isDerivedClassSelfOnly();
   }
 
+  /// True if this memory object is the 'self' of a root class init method.
+  bool isRootClassSelf() const {
+    return isClassInitSelf() && MemoryInst->isRootSelf();
+  }
+
   /// True if this memory object is the 'self' of a non-root class init method.
   bool isNonRootClassSelf() const {
     return isClassInitSelf() && !MemoryInst->isRootSelf();

lib/SILOptimizer/Mandatory/DefiniteInitialization.cpp

@@ -1071,7 +1071,13 @@ void LifetimeChecker::handleStoreUse(unsigned UseID) {
     // it for later.   Once we've collected all of the conditional init/assigns,
     // we can insert a single control variable for the memory object for the
     // whole function.
-    if (!Use.onlyTouchesTrivialElements(TheMemory))
+    //
+    // For root class initializers, we must keep track of initializations of
+    // trivial stored properties also, since we need to know when the object
+    // has been fully initialized when deciding if a strong_release should
+    // lower to a partial_dealloc_ref.
+    if (TheMemory.isRootClassSelf() ||
+        !Use.onlyTouchesTrivialElements(TheMemory))
       HasConditionalInitAssign = true;
     return;
   }
@@ -2276,7 +2282,13 @@ SILValue LifetimeChecker::handleConditionalInitAssign() {
     // If this ambiguous store is only of trivial types, then we don't need to
     // do anything special.  We don't even need keep the init bit for the
     // element precise.
-    if (Use.onlyTouchesTrivialElements(TheMemory))
+    //
+    // For root class initializers, we must keep track of initializations of
+    // trivial stored properties also, since we need to know when the object
+    // has been fully initialized when deciding if a strong_release should
+    // lower to a partial_dealloc_ref.
+    if (!TheMemory.isRootClassSelf() &&
+        Use.onlyTouchesTrivialElements(TheMemory))
       continue;
 
     B.setInsertionPoint(Use.Inst);