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Add comment on how tagged pointers are

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distinguished from normal (untagged) ones
as per review comment.

I am sufficiently unaquainted with doxygen to
defer the markup to someone with more experience.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57676 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Gabor Greif 2008-10-17 08:31:36 +00:00
parent 6784598895
commit 4fbed982fb
1 changed files with 8 additions and 1 deletions
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9
include/llvm/Use.h
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@ -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,