Swift SIL: escape effects for function arguments.

Store a list of argument effects in a function, which specify if and how arguments escape.
Such effects can be specified in the Swift source code (for details see docs/ReferenceGuides/UnderscoredAttributes.md) or derived in an optimization pass.

For details see the documentation in SwiftCompilerSources/Sources/SIL/Effects.swift.

include/swift/SIL/SILFunction.h

@@ -150,8 +150,9 @@ class SILFunction
   : public llvm::ilist_node<SILFunction>, public SILAllocated<SILFunction>,
     public SwiftObjectHeader {
     
-  static SwiftMetatype registeredMetatype;
-    
+private:
+  void *libswiftSpecificData[1];
+
 public:
   using BlockListType = llvm::iplist<SILBasicBlock>;
 
@@ -418,10 +419,6 @@ private:
   void setHasOwnership(bool newValue) { HasOwnership = newValue; }
 
 public:
-  static void registerBridgedMetatype(SwiftMetatype metatype) {
-    registeredMetatype = metatype;
-  }
-
   ~SILFunction();
 
   SILModule &getModule() const { return Module; }
@@ -943,6 +940,19 @@ public:
     EffectsKindAttr = unsigned(E);
   }
   
+  enum class ArgEffectKind {
+    Unknown,
+    Escape
+  };
+  
+  std::pair<const char *, int>  parseEffects(StringRef attrs, bool fromSIL,
+                                             bool isDerived,
+                                             ArrayRef<StringRef> paramNames);
+  void writeEffect(llvm::raw_ostream &OS, int effectIdx) const;
+  void copyEffects(SILFunction *from);
+  bool hasArgumentEffects() const;
+  void visitArgEffects(std::function<void(int, bool, ArgEffectKind)> c) const;
+
   Purpose getSpecialPurpose() const { return specialPurpose; }
 
   /// Get this function's global_init attribute.