<html>
<head>
<base href="https://llvm.org/bugs/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - LoopVectorizer does not properly preserve LoopInfo"
href="https://llvm.org/bugs/show_bug.cgi?id=26952">26952</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>LoopVectorizer does not properly preserve LoopInfo
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Loop Optimizer
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>anemet@apple.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=16040" name="attach_16040" title="testcase">attachment 16040</a> <a href="attachment.cgi?id=16040&action=edit" title="testcase">[details]</a></span>
testcase
On the attached testcase based on MultiSource/Benchmarks/nbench/nbench1.c, LV
fails to preserve LoopInfo. -verify-loop-info fails with:
$ opt before-vect-func.ll -targetlibinfo -tti -tbaa -scoped-noalias
-assumption-cache-tracker -forceattrs -inferattrs -loop-vectorize
-verify-loop-info
Assertion failed: (HasInsideLoopSuccs && "Loop block has no in-loop
successors!"), function verifyLoop, file
../include/llvm/Analysis/LoopInfoImpl.h, line 279.
This is the difference between what -loops and what LV produces:
@@ -21 +20,0 @@
- Loop at depth 2 containing:
%vector.body<header>,%pred.store.if,%13,%pred.store.continue,%pred.store.if2,%15,%pred.store.continue3<latch><exiting>
@@ -31,0 +31 @@
+ Loop at depth 2 containing:
%vector.body<header><exiting>,%pred.store.continue<exiting>,%pred.store.continue3<latch><exiting>
Bunch of blocks are missing, looks like all related to store predication.
I triggered this latent bug after making LoopLoadElimination dependent on
LoopSimplify. LoopSimplify trims many blocks because of corrupt LI:
LoopSimplify: Deleting edge from dead predecessor
LoopSimplify: Deleting edge from dead predecessor
LoopSimplify: Creating dedicated exit block .loopexit
LoopSimplify: Creating dedicated exit block .loopexit4
LoopSimplify: Creating dedicated exit block for.end31.loopexit</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>