PredictableMemOpt: Don't try to diagnose recursive value types.

They're invalid, and we don't want to blow the stack trying to decompose a type with infinite elements. Fixes rdar://problem/17920535.

Swift SVN r23775

include/swift/SIL/TypeLowering.h

@@ -155,6 +155,12 @@ public:
     return !isAddressOnly();
   }
   
+  /// True if the type was successfully lowered, false if there was an error
+  /// during type lowering.
+  virtual bool isValid() const {
+    return true;
+  }
+  
   /// isTrivial - Returns true if the type is trivial, meaning it is a loadable
   /// value type with no reference type members that require releasing.
   bool isTrivial() const {

lib/SIL/TypeLowering.cpp

@@ -895,7 +895,6 @@ namespace {
     AddressOnlyTypeLowering(SILType type)
       : TypeLowering(type, IsNotTrivial, IsAddressOnly) {}
 
-  public:
     void emitCopyInto(SILBuilder &B, SILLocation loc,
                       SILValue src, SILValue dest, IsTake_t isTake,
                       IsInitialization_t isInit) const override {
@@ -946,9 +945,15 @@ namespace {
     }
   };
   
-  /// A class that acts as a stand-in for unimplemented types.
-  class UnimplementedTypeLowering : public AddressOnlyTypeLowering {
-    using AddressOnlyTypeLowering::AddressOnlyTypeLowering;
+  /// A class that acts as a stand-in for improperly recursive types.
+  class RecursiveErrorTypeLowering : public AddressOnlyTypeLowering {
+  public:
+    RecursiveErrorTypeLowering(SILType type)
+      : AddressOnlyTypeLowering(type) {}
+    
+    bool isValid() const override {
+      return false;
+    }
   };
 
   /// Build the appropriate TypeLowering subclass for the given type.
@@ -1161,7 +1166,7 @@ const TypeLowering *TypeConverter::find(TypeKey k) {
                                          nomTy->getDeclaredTypeInContext());
     } else
       assert(false && "non-nominal types should not be recursive");
-    found->second = new (*this, k.isDependent()) UnimplementedTypeLowering(
+    found->second = new (*this, k.isDependent()) RecursiveErrorTypeLowering(
                                 SILType::getPrimitiveAddressType(k.SubstType));
   }
   return found->second;
@@ -1169,6 +1174,9 @@ const TypeLowering *TypeConverter::find(TypeKey k) {
 
 void TypeConverter::insert(TypeKey k, const TypeLowering *tl) {
   auto &Types = k.isDependent() ? DependentTypes : IndependentTypes;
+  // TODO: Types[k] should always be null at this point, except that we
+  // rely on type lowering to discover recursive value types right now.
+  if (!Types[k])
     Types[k] = tl;
 }
 

lib/SILPasses/PredictableMemOpt.cpp

@@ -31,6 +31,9 @@ STATISTIC(NumAllocRemoved, "Number of allocations completely removed");
 //===----------------------------------------------------------------------===//
 
 static unsigned getNumSubElements(SILType T, SILModule &M) {
+  if (!M.getTypeLowering(T).isValid())
+    return 0;
+
   if (auto TT = T.getAs<TupleType>()) {
     unsigned NumElements = 0;
     for (auto index : indices(TT.getElementTypes()))

test/SILGen/unsupported_recursive_value_type.swift

@@ -1,4 +1,4 @@
-// RUN: %swift -emit-silgen -verify %s
+// RUN: %swift -emit-sil -verify %s
 
 struct SelfRecursiveStruct { // expected-error{{recursive value type}}
   let a: SelfRecursiveStruct
@@ -37,3 +37,12 @@ enum RecursiveByGenericSubstitutionEnum<T> {
 struct RecursiveByGenericSubstitutionStruct { // expected-error{{recursive value type}}
   let a: RecursiveByGenericSubstitutionEnum<RecursiveByGenericSubstitutionStruct>
 }
+
+struct RecursiveWithLocal { // expected-error{{recursive value type 'RecursiveWithLocal' is not allowed}}
+  init(t: Local) { self.t = t }
+  struct Local {
+    init(s: RecursiveWithLocal) { self.s = s }
+    var s: RecursiveWithLocal
+  }
+  var t: Local
+}