<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 --- - [x86] Use pop to restore stack instead of add"
href="https://llvm.org/bugs/show_bug.cgi?id=26333">26333</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[x86] Use pop to restore stack instead of add
</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>normal
</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>hans@chromium.org
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Blocks</th>
<td>26299
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Consider the following at -Os:
struct S {
void foo();
};
S *bar(int);
void baz() {
bar(0)->foo();
}
Clang will generate:
00000000 <?baz@@YAXXZ>:
0: 6a 00 push $0x0
2: e8 00 00 00 00 call 7 <?baz@@YAXXZ+0x7>
7: 83 c4 04 add $0x4,%esp
a: 89 c1 mov %eax,%ecx
c: e9 00 00 00 00 jmp 11 <@feat.00+0x10>
Instead of 'add $0x4,%esp', MSVC would do 'pop %ecx' and save two bytes,
because %ecx isn't live there anyway.
This incurs a memory access, but since nothing depends on the result, maybe
that would be OK, at least at -Os?</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>