<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 --- - Compiler generating an unnecessary volatile load" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D24325&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=AE8E1C5m7rc0I6e3GfRJNEDWZEnDjk35sRsMOI23SPM&s=7oF2O1pN8Q6aP6w9Zzi-ZlPAPVQY6avBVIwPOBFJZKk&e=">24325</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Compiler generating an unnecessary volatile load
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>douglas_yung@playstation.sony.com
</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>This bug was found when trying to modify the clang lit test
CodeGenCXX\volatile.cpp to work when the compiler is in c++11 mode.
The repro is as follows:
volatile int *x;
void test() {
*x;
}
If you compile the code with trunk (I am using r242449) and give the option "-S
-emit-llvm", you get the following:
@x = global i32* null, align 8
; Function Attrs: nounwind uwtable
define void @_Z4testv() #0 {
entry:
%0 = load i32*, i32** @x, align 8
ret void
}
However if you also add the switch "-std=c++11", the code generated is the
following:
@x = global i32* null, align 8
; Function Attrs: nounwind uwtable
define void @_Z4testv() #0 {
entry:
%0 = load i32*, i32** @x, align 8
%1 = load volatile i32, i32* %0, align 4
ret void
}
Note that there is an extra load volatile that is generated in this case.</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>