diff options
| -rw-r--r-- | include/llvm/Use.h | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/include/llvm/Use.h b/include/llvm/Use.h index f88d4357c7..b4d2c48824 100644 --- a/include/llvm/Use.h +++ b/include/llvm/Use.h @@ -29,13 +29,20 @@ class User; // Generic Tagging Functions //===----------------------------------------------------------------------===// +// We adhere to the following convention: The type of a tagged pointer +// to T is T volatile*. This means that functions that superpose a tag +// on a pointer will be supplied a T* (or T const*) and will return a +// tagged one: T volatile*. Untagging functions do it the other way +// 'round. While this scheme does not prevent dereferencing of tagged +// pointers, proper type annotations do catch most inappropriate uses. + /// Tag - generic tag type for (at least 32 bit) pointers enum Tag { noTag, tagOne, tagTwo, tagThree }; /// addTag - insert tag bits into an (untagged) pointer template <typename T, typename TAG> inline volatile T *addTag(const T *P, TAG Tag) { - return reinterpret_cast<T*>(ptrdiff_t(P) | Tag); + return reinterpret_cast<T*>(ptrdiff_t(P) | Tag); } /// stripTag - remove tag bits from a pointer, |