<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 - super slow complication with -O3 on simple valid code (-O2: 0.1s VS -O3: 8min+)"
href="https://bugs.llvm.org/show_bug.cgi?id=51953">51953</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>super slow complication with -O3 on simple valid code (-O2: 0.1s VS -O3: 8min+)
</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>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>haoxintu@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Hi all.
The trunk of clang spends too much time compiling the following simple valid
code at -O3.
$cat small.c
#include <stdint.h>
ui_0 = 0x7DED4A39;
ui_1 = 0x8CD77211;
uli_3 = 0x0;
us_8 = 0x0;
li_9 = 0x94B16C262177BA8F;
c_11 = 0x0;
s_14 = 0x6A5F;
uli_15 = 0x8F4F05DD1902F8E5;
uint32_t ui_16 = 0xE91854DB;
int32_t func() {
for (uli_3 = 18; c_11 <= 40; c_11 += 1)
do {
ui_0 = 6;
for (; ui_0 > 2; ui_0--) {
c_11 = 7;
do {
(ui_16 &= s_14);
do {
ui_1 = -4;
do {
ui_1 += 4;
li_9 = 5;
do
if ((ui_16 &= s_14)) {
while (uli_15 > 2)
;
}
while (li_9--);
} while (ui_1 < 100);
} while (0);
} while (c_11--);
}
} while (us_8++);
}
$time clang -w -O2 -c small.c
real 0m0.118s
user 0m0.058s
sys 0m0.030s
$time clang -w -O3 -c small.c
real 8m37.672s
user 7m32.836s
sys 0m11.836s
$clang -v
clang version 14.0.0 (<a href="https://github.com/llvm/llvm-project">https://github.com/llvm/llvm-project</a>
ebc5feb4ed6b1f59a000669030f9639bf1763403)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/haoxin/haoxin-data/compilers/llvm-project/build/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
Reproduced in Godbolt: <a href="https://godbolt.org/z/vn5fqWe6f">https://godbolt.org/z/vn5fqWe6f</a>
Thanks
Haoxin</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>