Modifications to dyn_cast/cast to make them work for objects too, instead of only pointers.

The use case is if you have a wrapper class:

class Base {
  void *Ptr;
public:
  Base() : Ptr(0) { }
  operator bool() const { return Ptr; }
.....
}

and sub-wrappers that have exactly the same size:

class Sub : public Base {
public:
....
static bool classof(const Base*);
}

and in the code you would do:

void f(Base b) {
  Sub sub = dyn_cast<Sub>(b);
  if (sub) {
    ....
  }
}



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78424 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 4 deletions

diff --git a/include/llvm/Support/Casting.h b/include/llvm/Support/Casting.h
index 48988f8a6b..353611fc12 100644
--- a/include/llvm/Support/Casting.h
+++ b/include/llvm/Support/Casting.h
@@ -205,8 +205,9 @@ inline typename cast_retty<X, Y>::ret_type cast(const Y &Val) {
 // accepted.
 //
 template <class X, class Y>
-inline typename cast_retty<X, Y*>::ret_type cast_or_null(Y *Val) {
-  if (Val == 0) return 0;
+inline typename cast_retty<X, Y>::ret_type cast_or_null(const Y &Val) {
+  typedef typename cast_retty<X, Y>::ret_type ret_type;
+  if (!Val) return ret_type();
   assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
   return cast<X>(Val);
 }
@@ -222,7 +223,8 @@ inline typename cast_retty<X, Y*>::ret_type cast_or_null(Y *Val) {
 
 template <class X, class Y>
 inline typename cast_retty<X, Y>::ret_type dyn_cast(const Y &Val) {
-  return isa<X>(Val) ? cast<X, Y>(Val) : 0;
+  typedef typename cast_retty<X, Y>::ret_type ret_type;
+  return isa<X>(Val) ? cast<X, Y>(Val) : (ret_type)ret_type();
 }
 
 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
@@ -230,7 +232,8 @@ inline typename cast_retty<X, Y>::ret_type dyn_cast(const Y &Val) {
 //
 template <class X, class Y>
 inline typename cast_retty<X, Y>::ret_type dyn_cast_or_null(const Y &Val) {
-  return (Val && isa<X>(Val)) ? cast<X, Y>(Val) : 0;
+  typedef typename cast_retty<X, Y>::ret_type ret_type;
+  return (Val && isa<X>(Val)) ? cast<X, Y>(Val) : (ret_type)ret_type();
 }