From 21c60904ce6b937cb0c8744375e9c1a95fe0e495 Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Sat, 21 May 2011 19:13:10 +0000
Subject: [PATCH] PR7952: Make isa<> use the same logic as cast<>, so that they
 both work consistently.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131803 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/Support/Casting.h | 96 ++++++++++++++++------------------
 lib/Transforms/Scalar/SCCP.cpp |  2 +-
 2 files changed, 45 insertions(+), 53 deletions(-)

diff --git a/include/llvm/Support/Casting.h b/include/llvm/Support/Casting.h
index abb5a9aa11d..3aab4367f5b 100644
--- a/include/llvm/Support/Casting.h
+++ b/include/llvm/Support/Casting.h
@@ -23,8 +23,6 @@ namespace llvm {
 //                          isa<x> Support Templates
 //===----------------------------------------------------------------------===//
 
-template<typename FromCl> struct isa_impl_cl;
-
 // Define a template that can be specialized by smart pointers to reflect the
 // fact that they are automatically dereferenced, and are not involved with the
 // template selection process...  the default implementation is a noop.
@@ -43,12 +41,9 @@ template<typename From> struct simplify_type<const From> {
   }
 };
 
-
-// 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)) { ... }
-//
+// The core of the implementation of isa<X> is here; To and From should be
+// the names of classes.  This template can be specialized to customize the
+// implementation of isa<> without rewriting it from scratch.
 template <typename To, typename From>
 struct isa_impl {
   static inline bool doit(const From &Val) {
@@ -56,66 +51,63 @@ struct isa_impl {
   }
 };
 
-template<typename To, typename From, typename SimpleType>
+template <typename To, typename From> struct isa_impl_cl {
+  static inline bool doit(const From &Val) {
+    return isa_impl<To, From>::doit(Val);
+  }
+};
+
+template <typename To, typename From> struct isa_impl_cl<To, const From> {
+  static inline bool doit(const From &Val) {
+    return isa_impl<To, From>::doit(Val);
+  }
+};
+
+template <typename To, typename From> struct isa_impl_cl<To, From*> {
+  static inline bool doit(const From *Val) {
+    return isa_impl<To, From>::doit(*Val);
+  }
+};
+
+template <typename To, typename From> struct isa_impl_cl<To, const From*> {
+  static inline bool doit(const From *Val) {
+    return isa_impl<To, From>::doit(*Val);
+  }
+};
+
+template <typename To, typename From> struct isa_impl_cl<To, const From*const> {
+  static inline bool doit(const From *Val) {
+    return isa_impl<To, From>::doit(*Val);
+  }
+};
+
+template<typename To, typename From, typename SimpleFrom>
 struct isa_impl_wrap {
   // When From != SimplifiedType, we can simplify the type some more by using
   // the simplify_type template.
   static bool doit(const From &Val) {
-    return isa_impl_cl<const SimpleType>::template
-                    isa<To>(simplify_type<const From>::getSimplifiedValue(Val));
+    return isa_impl_wrap<To, SimpleFrom,
+      typename simplify_type<SimpleFrom>::SimpleType>::doit(
+                          simplify_type<From>::getSimplifiedValue(Val));
   }
 };
 
 template<typename To, typename FromTy>
-struct isa_impl_wrap<To, const FromTy, const FromTy> {
+struct isa_impl_wrap<To, FromTy, FromTy> {
   // When From == SimpleType, we are as simple as we are going to get.
   static bool doit(const FromTy &Val) {
-    return isa_impl<To,FromTy>::doit(Val);
+    return isa_impl_cl<To,FromTy>::doit(Val);
   }
 };
 
-// isa_impl_cl - Use class partial specialization to transform types to a single
-// canonical form for isa_impl.
+// 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<typename FromCl>
-struct isa_impl_cl {
-  template<class ToCl>
-  static bool isa(const FromCl &Val) {
-    return isa_impl_wrap<ToCl,const FromCl,
-                   typename simplify_type<const FromCl>::SimpleType>::doit(Val);
-  }
-};
-
-// Specialization used to strip const qualifiers off of the FromCl type...
-template<typename FromCl>
-struct isa_impl_cl<const FromCl> {
-  template<class ToCl>
-  static bool isa(const FromCl &Val) {
-    return isa_impl_cl<FromCl>::template isa<ToCl>(Val);
-  }
-};
-
-// Define pointer traits in terms of base traits...
-template<class FromCl>
-struct isa_impl_cl<FromCl*> {
-  template<class ToCl>
-  static bool isa(FromCl *Val) {
-    return isa_impl_cl<FromCl>::template isa<ToCl>(*Val);
-  }
-};
-
-// Define reference traits in terms of base traits...
-template<class FromCl>
-struct isa_impl_cl<FromCl&> {
-  template<class ToCl>
-  static bool isa(FromCl &Val) {
-    return isa_impl_cl<FromCl>::template isa<ToCl>(&Val);
-  }
-};
-
 template <class X, class Y>
 inline bool isa(const Y &Val) {
-  return isa_impl_cl<Y>::template isa<X>(Val);
+  return isa_impl_wrap<X, Y, typename simplify_type<Y>::SimpleType>::doit(Val);
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index db8eb850448..083412ed942 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -655,7 +655,7 @@ bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
   
   // Just mark all destinations executable!
   // TODO: This could be improved if the operand is a [cast of a] BlockAddress.
-  if (isa<IndirectBrInst>(&TI))
+  if (isa<IndirectBrInst>(TI))
     return true;
   
 #ifndef NDEBUG