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Document type upreferences (PR3380), patch by Stein Roger Skafløtten

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with enhancements and corrections by me.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63502 91177308-0d34-0410-b5e6-96231b3b80d8
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Chris Lattner 2009-02-02 07:32:36 +00:00
parent 91dad87ddc
commit 242d61d1c9
1 changed files with 53 additions and 1 deletions
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docs/LangRef.html
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@ -55,6 +55,7 @@
<li><a href="#t_opaque">Opaque Type</a></li>
</ol>
</li>
<li><a href="#t_uprefs">Type Up-references</a></li>
</ol>
</li>
<li><a href="#constants">Constants</a>
@ -722,7 +723,6 @@ change.</p>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="globalvars">Global Variables</a>
@ -1646,6 +1646,58 @@ structure type).</p>
</table>
</div>
<!-- ======================================================================= -->
<div class="doc_subsection">
<a name="t_uprefs">Type Up-references</a>
</div>
<div class="doc_text">
<h5>Overview:</h5>
<p>
An "up reference" allows you to refer to a lexically enclosing type without
requiring it to have a name. For instance, a structure declaration may contain a
pointer to any of the types it is lexically a member of. Example of up
references (with their equivalent as named type declarations) include:</p>
<pre>
{ \2 * } %x = type { %t* }
{ \2 }* %y = type { %y }*
\1* %z = type %z*
</pre>
<p>
An up reference is needed by the asmprinter for printing out cyclic types when
there is no declared name for a type in the cycle. Because the asmprinter does
not want to print out an infinite type string, it needs a syntax to handle
recursive types that have no names (all names are optional in llvm IR).
</p>
<h5>Syntax:</h5>
<pre>
\&lt;level&gt;
</pre>
<p>
The level is the count of the lexical type that is being referred to.
</p>
<h5>Examples:</h5>
<table class="layout">
<tr class="layout">
<td class="left"><tt>\1*</tt></td>
<td class="left">Self-referential pointer.</td>
</tr>
<tr class="layout">
<td class="left"><tt>{ { \3*, i8 }, i32 }</tt></td>
<td class="left">Recursive structure where the upref refers to the out-most
structure.</td>
</tr>
</table>
</div>
</div>
<!-- *********************************************************************** -->
<div class="doc_section"> <a name="constants">Constants</a> </div>