Replace the PointerLikeTypeTraits::getNumLowBitsAvailable

function with a new NumLowBitsAvailable enum, which makes the
value available as an integer constant expression.

Add PointerLikeTypeTraits specializations for Instruction* and
Use** since they are only guaranteed 4-byte aligned.

Enhance PointerIntPair to know about (and enforce) the alignment
specified by PointerLikeTypeTraits.  This should allow things 
like PointerIntPair<PointerIntPair<void*, 1,bool>, 1, bool> 
because the inner one knows that 2 low bits are free.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67979 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 2 deletions

diff --git a/include/llvm/Use.h b/include/llvm/Use.h
index cde4366a5a..53df699e70 100644
--- a/include/llvm/Use.h
+++ b/include/llvm/Use.h
@@ -24,11 +24,21 @@ namespace llvm {
 
 class Value;
 class User;
-
+class Use;
 
 /// Tag - generic tag type for (at least 32 bit) pointers
 enum Tag { noTag, tagOne, tagTwo, tagThree };
 
+// Use** is only 4-byte aligned.
+template<>
+class PointerLikeTypeTraits<Use**> {
+public:
+  static inline void *getAsVoidPointer(Use** P) { return P; }
+  static inline Use **getFromVoidPointer(void *P) {
+    return static_cast<Use**>(P);
+  }
+  enum { NumLowBitsAvailable = 2 };
+};
 
 //===----------------------------------------------------------------------===//
 //                                  Use Class
@@ -212,7 +222,7 @@ template<> struct simplify_type<value_use_iterator<const User> > {
 
 template<> struct simplify_type<const value_use_iterator<const User> >
   : public simplify_type<value_use_iterator<const User> > {};
-
+ 
 } // End llvm namespace
 
 #endif