80 column rule.

[oota-llvm.git] / docs / LangRef.html

diff --git a/docs/LangRef.html b/docs/LangRef.html
index f2d7d8d1680c0ad3c9ec4a784ece99cedf3843c2..88970f971ecad8cb4e3c9cc23e262003e1555c22 100644 (file)
--- a/docs/LangRef.html
+++ b/docs/LangRef.html
@@ -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>
@@ -1344,6 +1344,13 @@ value.</p>
   </tr>
   </tbody>
 </table>
+
+<p>Note that the code generator does not yet support large integer types
+to be used as function return types. The specific limit on how large a
+return type the code generator can currently handle is target-dependent;
+currently it's often 64 bits for 32-bit targets and 128 bits for 64-bit
+targets.</p>
+
 </div>
 
 <!-- _______________________________________________________________________ -->
@@ -1404,6 +1411,11 @@ As a special case, however, zero length arrays are recognized to be variable
 length.  This allows implementation of 'pascal style arrays' with the  LLVM
 type "{ i32, [0 x float]}", for example.</p>
 
+<p>Note that the code generator does not yet support large aggregate types
+to be used as function return types. The specific limit on how large an
+aggregate return type the code generator can currently handle is
+target-dependent, and also dependent on the aggregate element types.</p>
+
 </div>
 
 <!-- _______________________________________________________________________ -->
@@ -1489,6 +1501,12 @@ instruction.</p>
       an <tt>i32</tt>.</td>
   </tr>
 </table>
+
+<p>Note that the code generator does not yet support large aggregate types
+to be used as function return types. The specific limit on how large an
+aggregate return type the code generator can currently handle is
+target-dependent, and also dependent on the aggregate element types.</p>
+
 </div>
 
 <!-- _______________________________________________________________________ -->
@@ -1593,6 +1611,12 @@ be any integer or floating point type.</p>
     <td class="left">Vector of 2 64-bit integer values.</td>
   </tr>
 </table>
+
+<p>Note that the code generator does not yet support large vector types
+to be used as function return types. The specific limit on how large a
+vector return type codegen can currently handle is target-dependent;
+currently it's often a few times longer than a hardware vector register.</p>
+
 </div>
 
 <!-- _______________________________________________________________________ -->
@@ -1622,6 +1646,56 @@ 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 class="doc_section"> <a name="constants">Constants</a> </div>
@@ -2042,8 +2116,13 @@ return value.</p>
   ret { i32, i8 } { i32 4, i8 2 } <i>; Return an aggregate of values 4 and 2</i>
 </pre>
 
-<p>Note that the code generator does not yet fully support larger
-   aggregate return values.</p>
+<p>Note that the code generator does not yet fully support large
+   return values. The specific sizes that are currently supported are
+   dependent on the target. For integers, on 32-bit targets the limit
+   is often 64 bits, and on 64-bit targets the limit is often 128 bits.
+   For aggregate types, the current limits are dependent on the element
+   types; for example targets are often limited to 2 total integer
+   elements and 2 total floating-point elements.</p>
 
 </div>
 <!-- _______________________________________________________________________ -->