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Add a comment to refer to the section of the programmer's manual that explains what the pointer tagging in Use is for.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70521 91177308-0d34-0410-b5e6-96231b3b80d8
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Stefanus Du Toit 2009-04-30 23:28:50 +00:00
parent a26eae64dd
commit c26672a2d2
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9
include/llvm/Use.h
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@ -11,6 +11,15 @@
// instruction or some other User instance which refers to a Value. The Use // instruction or some other User instance which refers to a Value. The Use
// class keeps the "use list" of the referenced value up to date. // class keeps the "use list" of the referenced value up to date.
// //
// Pointer tagging is used to efficiently find the User corresponding
// to a Use without having to store a User pointer in every Use. A
// User is preceded in memory by all the Uses corresponding to its
// operands, and the low bits of one of the fields (Prev) of the Use
// class are used to encode offsets to be able to find that User given
// a pointer to any Use. For details, see:
//
// http://www.llvm.org/docs/ProgrammersManual.html#UserLayout
//
//===----------------------------------------------------------------------===// //===----------------------------------------------------------------------===//
#ifndef LLVM_USE_H #ifndef LLVM_USE_H