Cleanup the simplify_type implementation.

As far as simplify_type is concerned, there are 3 kinds of smart pointers:

* const correct: A 'const MyPtr<int> &' produces a 'const int*'. A
'MyPtr<int> &' produces a 'int *'.
* always const: Even a 'MyPtr<int> &' produces a 'const int*'.
* no const: Even a 'const MyPtr<int> &' produces a 'int*'.

This patch then does the following:

* Removes the unused specializations. Since they are unused, it is hard
to know which kind should be implemented.
* Make sure we don't drop const.
* Fix the default forwarding so that const correct pointer only need
one specialization.
* Simplifies the existing specializations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178147 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 41 deletions

diff --git a/include/llvm/Support/ValueHandle.h b/include/llvm/Support/ValueHandle.h
index db44995d95..b49341c3ff 100644
--- a/include/llvm/Support/ValueHandle.h
+++ b/include/llvm/Support/ValueHandle.h
@@ -20,6 +20,7 @@
 
 namespace llvm {
 class ValueHandleBase;
+template<typename From> struct simplify_type;
 
 // ValueHandleBase** is only 4-byte aligned.
 template<>
@@ -162,14 +163,12 @@ public:
 
 // Specialize simplify_type to allow WeakVH to participate in
 // dyn_cast, isa, etc.
-template<typename From> struct simplify_type;
-template<> struct simplify_type<const WeakVH> {
+template<> struct simplify_type<WeakVH> {
   typedef Value* SimpleType;
-  static SimpleType getSimplifiedValue(const WeakVH &WVH) {
-    return static_cast<Value *>(WVH);
+  static SimpleType getSimplifiedValue(WeakVH &WVH) {
+    return WVH;
   }
 };
-template<> struct simplify_type<WeakVH> : public simplify_type<const WeakVH> {};
 
 /// AssertingVH - This is a Value Handle that points to a value and asserts out
 /// if the value is destroyed while the handle is still live.  This is very
@@ -236,18 +235,6 @@ public:
   ValueTy &operator*() const { return *getValPtr(); }
 };
 
-// Specialize simplify_type to allow AssertingVH to participate in
-// dyn_cast, isa, etc.
-template<typename From> struct simplify_type;
-template<> struct simplify_type<const AssertingVH<Value> > {
-  typedef Value* SimpleType;
-  static SimpleType getSimplifiedValue(const AssertingVH<Value> &AVH) {
-    return static_cast<Value *>(AVH);
-  }
-};
-template<> struct simplify_type<AssertingVH<Value> >
-  : public simplify_type<const AssertingVH<Value> > {};
-
 // Specialize DenseMapInfo to allow AssertingVH to participate in DenseMap.
 template<typename T>
 struct DenseMapInfo<AssertingVH<T> > {
@@ -345,18 +332,6 @@ public:
   ValueTy &operator*() const { return *getValPtr(); }
 };
 
-// Specialize simplify_type to allow TrackingVH to participate in
-// dyn_cast, isa, etc.
-template<typename From> struct simplify_type;
-template<> struct simplify_type<const TrackingVH<Value> > {
-  typedef Value* SimpleType;
-  static SimpleType getSimplifiedValue(const TrackingVH<Value> &AVH) {
-    return static_cast<Value *>(AVH);
-  }
-};
-template<> struct simplify_type<TrackingVH<Value> >
-  : public simplify_type<const TrackingVH<Value> > {};
-
 /// CallbackVH - This is a value handle that allows subclasses to define
 /// callbacks that run when the underlying Value has RAUW called on it or is
 /// destroyed.  This class can be used as the key of a map, as long as the user
@@ -399,18 +374,6 @@ public:
   virtual void allUsesReplacedWith(Value *);
 };
 
-// Specialize simplify_type to allow CallbackVH to participate in
-// dyn_cast, isa, etc.
-template<typename From> struct simplify_type;
-template<> struct simplify_type<const CallbackVH> {
-  typedef Value* SimpleType;
-  static SimpleType getSimplifiedValue(const CallbackVH &CVH) {
-    return static_cast<Value *>(CVH);
-  }
-};
-template<> struct simplify_type<CallbackVH>
-  : public simplify_type<const CallbackVH> {};
-
 } // End llvm namespace
 
 #endif