<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 - MemCpyOpt: uses sext instead of zext for memcpy/memset size subtraction"
href="https://bugs.llvm.org/show_bug.cgi?id=47697">47697</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>MemCpyOpt: uses sext instead of zext for memcpy/memset size subtraction
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</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>Keywords</th>
<td>miscompilation
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>nunoplopes@sapo.pt
</td>
</tr>
<tr>
<th>CC</th>
<td>ahmed@bougacha.org, benny.kra@gmail.com, florian_hahn@apple.com, juneyoung.lee@sf.snu.ac.kr, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Test: Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
MemCpyOpt sign-extends the difference between memcpy/memset sizes instead of
zero-extending them.
<a href="https://alive2.llvm.org/ce/z/RgKeyt">https://alive2.llvm.org/ce/z/RgKeyt</a>
----------------------------------------
define void @src(* %dst, * %src, i8 %dst_size, i8 %src_size, i8 %c) {
memset * %dst align 1, i8 %c, i8 %dst_size
memcpy * %dst align 1, * %src align 1, i8 %src_size
ret void
}
=>
define void @src(* %dst, * %src, i8 %dst_size, i8 %src_size, i8 %c) {
%1 = usub_sat i8 %dst_size, %src_size
%2 = sext i8 %src_size to i64
%3 = gep * %dst, 1 x i64 %2
memset * %3 align 1, i8 %c, i8 %1
memcpy * %dst align 1, * %src align 1, i8 %src_size
ret void
}
Transformation doesn't verify!
ERROR: Source is more defined than target
Example:
* %dst = pointer(non-local, block_id=1, offset=96)
* %src = pointer(non-local, block_id=1, offset=9007199254741152)
i8 %dst_size = #x83 (131, -125)
i8 %src_size = #x82 (130, -126)
i8 %c = any
Source:
SOURCE MEMORY STATE
===================
NON-LOCAL BLOCKS:
Block 0 > size: 0 align: 1 alloc type: 0
Block 1 > size: 2305843009213693952 align: 2 alloc type: 0
Block 2 > align: 2 alloc type: 0
Target:
i8 %1 = #x01 (1)
i64 %2 = #xffffffffffffff82 (18446744073709551490, -126)
* %3 = pointer(non-local, block_id=1, offset=-30)
Summary:
0 correct transformations
1 incorrect transformations
0 Alive2 errors
<a href="https://web.ist.utl.pt/nuno.lopes/alive2/index.php?hash=1546033e6d866cfc&test=Transforms%2FMemCpyOpt%2Fmemset-memcpy-redundant-memset.ll">https://web.ist.utl.pt/nuno.lopes/alive2/index.php?hash=1546033e6d866cfc&test=Transforms%2FMemCpyOpt%2Fmemset-memcpy-redundant-memset.ll</a></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>