# [llvm-commits] [llvm] r167688 - /llvm/trunk/docs/ReleaseNotes.html

Sat Nov 10 22:47:52 PST 2012

```Author: nadav
Date: Sun Nov 11 00:47:51 2012
New Revision: 167688

URL: http://llvm.org/viewvc/llvm-project?rev=167688&view=rev
Log:
Update the vectorizer docs.

Modified:
llvm/trunk/docs/ReleaseNotes.html

Modified: llvm/trunk/docs/ReleaseNotes.html
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/ReleaseNotes.html?rev=167688&r1=167687&r2=167688&view=diff
==============================================================================
--- llvm/trunk/docs/ReleaseNotes.html (original)
+++ llvm/trunk/docs/ReleaseNotes.html Sun Nov 11 00:47:51 2012
@@ -473,15 +473,31 @@
<b>-mllvm -force-vector-width=4</b>.
The default value is <b>0</b> which means auto-select.
<br/>
-    We can now vectorize this code:
+    We can now vectorize this function:

<pre class="doc_code">
-    for (i=0; i<n; i++) {
-      a[i] = b[i+1] + c[i+3] + i;
-      sum += d[i];
+    unsigned sum_arrays(int *A, int *B, int start, int end) {
+      unsigned sum = 0;
+      for (int i = start; i < end; ++i)
+        sum += A[i] + B[i] + i;
+
+      return sum;
}
</pre>

+    We vectorize under the following loops:
+    <ul>
+    <li>The inner most loops must have a single basic block.</li>
+    <li>The number of iterations are known before the loop starts to execute.</li>
+    <li>The loop counter needs to be incrimented by one.</li>
+    <li>The loop trip count <b>can</b> be a variable.</li>
+    <li>Loops do <b>not</b> need to start at zero.</li>
+    <li>The induction variable can be used inside the loop.</li>
+    <li>Loop reductions are supported.</li>
+    <li>Arrays with affine access pattern do <b>not</b> need to be marked as 'noalias' and are checked at runtime.</li>
+    <li>...</li>
+    </ul>
+
</p>

<p>SROA - We've re-written SROA to be significantly more powerful.

```