Pull casting operators out of Value.h

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2166 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 80 insertions, 0 deletions

diff --git a/include/llvm/Support/Casting.h b/include/llvm/Support/Casting.h
new file mode 100644
index 0000000000..e59b7c2d07
--- /dev/null
+++ b/include/llvm/Support/Casting.h
@@ -0,0 +1,80 @@
+//===-- Support/Casting.h - Allow flexible, checked, casts -------*- C++ -*--=//
+//
+// This file defines the isa<X>(), cast<X>(), dyn_cast<X>(), cast_or_null<X>(),
+// and dyn_cast_or_null<X>() templates.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SUPPORT_CASTING_H
+#define SUPPORT_CASTING_H
+
+// real_type - Provide a macro to get the real type of a value that might be 
+// a use.  This provides a typedef 'Type' that is the argument type for all
+// non UseTy types, and is the contained pointer type of the use if it is a
+// UseTy.
+//
+template <class X> class real_type { typedef X Type; };
+
+//===----------------------------------------------------------------------===//
+//                          Type Checking Templates
+//===----------------------------------------------------------------------===//
+
+// isa<X> - Return true if the parameter to the template is an instance of the
+// template type argument.  Used like this:
+//
+//  if (isa<Type>(myVal)) { ... }
+//
+template <class X, class Y>
+inline bool isa(Y Val) {
+  assert(Val && "isa<Ty>(NULL) invoked!");
+  return X::classof(Val);
+}
+
+
+// cast<X> - Return the argument parameter cast to the specified type.  This
+// casting operator asserts that the type is correct, so it does not return null
+// on failure.  But it will correctly return NULL when the input is NULL.
+// Used Like this:
+//
+//  cast<      Instruction>(myVal)->getParent()
+//  cast<const Instruction>(myVal)->getParent()
+//
+template <class X, class Y>
+inline X *cast(Y Val) {
+  assert(isa<X>(Val) && "cast<Ty>() argument of uncompatible type!");
+  return (X*)(real_type<Y>::Type)Val;
+}
+
+// cast_or_null<X> - Functionally identical to cast, except that a null value is
+// accepted.
+//
+template <class X, class Y>
+inline X *cast_or_null(Y Val) {
+  assert((Val == 0 || isa<X>(Val)) &&
+         "cast_or_null<Ty>() argument of uncompatible type!");
+  return (X*)(real_type<Y>::Type)Val;
+}
+
+
+// dyn_cast<X> - Return the argument parameter cast to the specified type.  This
+// casting operator returns null if the argument is of the wrong type, so it can
+// be used to test for a type as well as cast if successful.  This should be
+// used in the context of an if statement like this:
+//
+//  if (const Instruction *I = dyn_cast<const Instruction>(myVal)) { ... }
+//
+
+template <class X, class Y>
+inline X *dyn_cast(Y Val) {
+  return isa<X>(Val) ? cast<X>(Val) : 0;
+}
+
+// dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
+// value is accepted.
+//
+template <class X, class Y>
+inline X *dyn_cast_or_null(Y Val) {
+  return (Val && isa<X>(Val)) ? cast<X>(Val) : 0;
+}
+
+#endif