Add a dereferenceable attribute

This attribute indicates that the parameter or return pointer is
dereferenceable. Practically speaking, loads from such a pointer within the
associated byte range are safe to speculatively execute. Such pointer
parameters are common in source languages (C++ references, for example).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213385 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Bitcode/LLVMBitCodes.h

@@ -374,7 +374,8 @@ namespace bitc {
     ATTR_KIND_OPTIMIZE_NONE = 37,
     ATTR_KIND_IN_ALLOCA = 38,
     ATTR_KIND_NON_NULL = 39,
-    ATTR_KIND_JUMP_TABLE = 40
+    ATTR_KIND_JUMP_TABLE = 40,
+    ATTR_KIND_DEREFERENCEABLE = 41
   };
 
   enum ComdatSelectionKindCodes {