<html>
<head>
<base href="https://bugs.llvm.org/">
</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 - Wrong code generated for simple memory move loop"
href="https://bugs.llvm.org/show_bug.cgi?id=46335">46335</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Wrong code generated for simple memory move loop
</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>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>carrot@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
</td>
</tr></table>
<p>
<div>
<pre>Compile following code with -O2
typedef struct SS
{
int d[3];
int a[6][4];
} S;
void foo(int d, S *p)
{
int i;
for (i = 0; i < 3; i++)
{
p->a[d][i] = p->a[d][i+1];
}
}
I got:
# %bb.0: # %entry
movslq %edi, %rax
shlq $4, %rax
movl 24(%rax,%rsi), %ecx
movl %ecx, 20(%rsi,%rax) // over written before read out
movq 16(%rax,%rsi), %rcx
movq %rcx, 12(%rsi,%rax)
retq
The 4 bytes word at 20(%rsi,%rax) is over written before read out, causes wrong
result at 16(%rsi,%rax).</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>