+</div>
+<!-- ======================================================================= -->
+<div class="doc_subsection">
+ <a name="sibcallopt">Sibling call optimization</a>
+</div>
+
+<div class="doc_text">
+
+<p>Sibling call optimization is a restricted form of tail call optimization.
+ Unlike tail call optimization described in the previous section, it can be
+ performed automatically on any tail calls when <tt>-tailcallopt</tt> option
+ is not specified.</p>
+
+<p>Sibling call optimization is currently performed on x86/x86-64 when the
+ following constraints are met:</p>
+
+<ul>
+ <li>Caller and callee have the same calling convention. It can be either
+ <tt>c</tt> or <tt>fastcc</tt>.
+
+ <li>The call is a tail call - in tail position (ret immediately follows call
+ and ret uses value of call or is void).</li>
+
+ <li>Caller and callee have matching return type or the callee result is not
+ used.
+
+ <li>If any of the callee arguments are being passed in stack, they must be
+ available in caller's own incoming argument stack and the frame offsets
+ must be the same.
+</ul>
+
+<p>Example:</p>
+<div class="doc_code">
+<pre>
+declare i32 @bar(i32, i32)
+
+define i32 @foo(i32 %a, i32 %b, i32 %c) {
+entry:
+ %0 = tail call i32 @bar(i32 %a, i32 %b)
+ ret i32 %0
+}
+</pre>
+</div>
+