<html>
<head>
<base href="http://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 --- - DeadStoreElimination ("-dse") eliminates a store that isn't dead"
href="http://llvm.org/bugs/show_bug.cgi?id=15822">15822</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>DeadStoreElimination ("-dse") eliminates a store that isn't dead
</td>
</tr>
<tr>
<th>Product</th>
<td>tools
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>All
</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>opt
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>mseaborn@chromium.org
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>DeadStoreElimination ("-dse") eliminates a store that isn't dead.
In the following test case, which is a reduced version of
SingleSource/UnitTests/byval-alignment.c from the LLVM test suite, @do_copy()
should set @g0 to 1234:
@g0 = global i32 zeroinitializer, align 4
@init_val = global i32 1234, align 4
declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32,
i1)
define void @f0(i8* %y) noinline {
tail call void @llvm.memcpy.p0i8.p0i8.i32(i8* bitcast (i32* @g0 to i8*), i8*
%y, i32 4, i32 1, i1 false)
ret void
}
define void @do_copy() {
%copy = alloca i32, align 4
%copy_cast = bitcast i32* %copy to i8*
%init_val_cast = bitcast i32* @init_val to i8*
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %copy_cast, i8* %init_val_cast, i32
4, i32 1, i1 false)
tail call void @f0(i8* %copy_cast)
ret void
}
However, "-dse" removes the memcpy() from @do_copy so that it will copy
uninitialised data to @g0:
$ opt -basicaa -dse byval-min.ll -S -o -
...
define void @do_copy() {
%copy = alloca i32, align 4
%copy_cast = bitcast i32* %copy to i8*
tail call void @f0(i8* %copy_cast)
ret void
}
This also occurs with "opt -std-link-opts".
This occurs in at least LLVM 3.0, 3.1 and r176253.</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>