[Definite initialization] Recognize delegation to a C function imported as an initializer.

Add yet one more flavor of hack to DI to recognize where we are
delegating the initialization of 'self'. The existing hack in this
area (for Objective-C factory initializers) is based on recognizing
the value_metatype instruction that feeds into the application of the
factory initializer. C functions imported as initializers don't have a
metatype argument, so instead tag the assignment into the self box as
the initialization of self.

As a minor cleanup in this area, don't emit the dead value_metatype
instruction when invoking a C-imported factory initializer.

Author: DougGregor

lib/SILGen/SILGenApply.cpp

@@ -1372,7 +1372,7 @@ class SILGenApply : public Lowering::ExprVisitor<SILGenApply> {
     auto nominal = ctorRef->getDecl()->getDeclContext()
                      ->getAsNominalTypeOrNominalTypeExtensionContext();
     bool useAllocatingCtor;
-    
+
     // Value types only have allocating initializers.
     if (isa<StructDecl>(nominal) || isa<EnumDecl>(nominal))
       useAllocatingCtor = true;
@@ -1406,7 +1406,11 @@ class SILGenApply : public Lowering::ExprVisitor<SILGenApply> {
       selfFormalType = CanMetatypeType::get(
           selfFormalType->getInOutObjectType()->getCanonicalType());
 
-      if (SGF.AllocatorMetatype)
+      // If the initializer is a C function imported as a member,
+      // there is no 'self' parameter. Mark it undef.
+      if (ctorRef->getDecl()->isImportAsMember())
+        self = SGF.emitUndef(expr, selfFormalType);
+      else if (SGF.AllocatorMetatype)
         self = emitCorrespondingSelfValue(
                  ManagedValue::forUnmanaged(SGF.AllocatorMetatype),
                  arg);

lib/SILOptimizer/Mandatory/DIMemoryUseCollector.cpp

@@ -1279,11 +1279,23 @@ void ElementUseCollector::collectDelegatingClassInitSelfUses() {
     if (isa<StoreInst>(User) && UI->getOperandNumber() == 1)
       continue;
 
-    // For class initializers, the assign into the self box is captured as
-    // a SelfInit or SuperInit elsewhere.
+    // For class initializers, the assign into the self box may be
+    // captured as SelfInit or SuperInit elsewhere.
     if (TheMemory.isClassInitSelf() &&
-        isa<AssignInst>(User) && UI->getOperandNumber() == 1)
+        isa<AssignInst>(User) && UI->getOperandNumber() == 1) {
+      // If the source of the assignment is an application of a C
+      // function, there is no metatype argument, so treat the
+      // assignment to the self box as the initialization.
+      if (auto apply = dyn_cast<ApplyInst>(cast<AssignInst>(User)->getSrc())) {
+        if (auto fn = apply->getCalleeFunction()) {
+          if (fn->getRepresentation()
+                == SILFunctionTypeRepresentation::CFunctionPointer)
+            Uses.push_back(DIMemoryUse(User, DIUseKind::SelfInit, 0, 1));
+        }
+      }
+
       continue;
+    }
 
     // Stores *to* the allocation are writes.  If the value being stored is a
     // call to self.init()... then we have a self.init call.

test/SILGen/import_as_member.swift

@@ -39,6 +39,7 @@ public func useClass(d: Double, opts: SomeClass.Options) {
 extension SomeClass {
   // SIL-LABEL: sil hidden @_TFE16import_as_memberCSo9SomeClasscfT6doubleSd_S0_
   // SIL: bb0([[DOUBLE:%[0-9]+]] : $Double
+  // SIL-NOT: value_metatype
   // SIL: [[FNREF:%[0-9]+]] = function_ref @MakeIAMSomeClass
   // SIL: apply [[FNREF]]([[DOUBLE]])
   convenience init(double: Double) {

test/SILOptimizer/definite_init_objc_factory_init.swift

@@ -1,8 +1,9 @@
-// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) %s -emit-sil | FileCheck %s
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -I %S/../IDE/Inputs/custom-modules %s -emit-sil | FileCheck %s
 
 // REQUIRES: objc_interop
 
 import Foundation
+import ImportAsMember.Class
 
 // CHECK-LABEL: sil shared [thunk] @_TTOFCSo4HiveCfT5queenGSQCSo3Bee__GSQS__ : $@convention(thin) (@owned ImplicitlyUnwrappedOptional<Bee>, @thick Hive.Type) -> @owned ImplicitlyUnwrappedOptional<Hive>
 func testInstanceTypeFactoryMethod(queen: Bee) {
@@ -39,3 +40,14 @@ extension Hive {
     try self.init(flakyQueen: other)
   }
 }
+
+extension SomeClass {
+  // SIL-LABEL: sil hidden @_TFE16import_as_memberCSo9SomeClasscfT6doubleSd_S0_
+  // SIL: bb0([[DOUBLE:%[0-9]+]] : $Double
+  // SIL-NOT: value_metatype
+  // SIL: [[FNREF:%[0-9]+]] = function_ref @MakeIAMSomeClass
+  // SIL: apply [[FNREF]]([[DOUBLE]])
+  convenience init(double: Double) {
+    self.init(value: double)
+  }
+}