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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - fatal error: error in backend: Instruction Combining seems stuck in an infinite loop after 100 iterations"
href="https://bugs.llvm.org/show_bug.cgi?id=49670">49670</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>fatal error: error in backend: Instruction Combining seems stuck in an infinite loop after 100 iterations
</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>All
</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.
Clang crashes on this valid program under -O3 only. Note that this issue only
occurs in the current trunk version of clang, clang-12 (including) downwards
versions handle this case well.
$cat small.c
#include <stdint.h>
uint8_t a, d, c, b;
void e() {
int64_t *f = e;
b = a ? *f : 0;
int g = 10;
for (; g; g--) {
c = 0;
for (; c <= 30; c++)
;
d = 26;
for (; d <= 42; d++) {
int64_t *i = e;
(a -= (a %= *i) < (c > 31)) || (b /= *i);
}
}
}
$clang -w -O3 small.c
fatal error: error in backend: Instruction Combining seems stuck in an infinite
loop after 100 iterations.
clang-13: error: clang frontend command failed with exit code 70 (use -v to see
invocation)
clang version 13.0.0 (<a href="https://github.com/llvm/llvm-project">https://github.com/llvm/llvm-project</a>
bed9933a461e7b3d0c8c5a8fa770aa1b49802660)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/tuhaoxin/github/llvm-project/build-20210320/bin
clang-13: note: diagnostic msg:
********************
PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-13: note: diagnostic msg: /tmp/small-5d6471.c
clang-13: note: diagnostic msg: /tmp/small-5d6471.sh
clang-13: note: diagnostic msg:
********************
$clang -v
clang version 13.0.0 (<a href="https://github.com/llvm/llvm-project">https://github.com/llvm/llvm-project</a>
bed9933a461e7b3d0c8c5a8fa770aa1b49802660)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/tuhaoxin/github/llvm-project/build-20210320/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
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
Selected multilib: .;@m64
By the way, I'm not sure if this is the same problem as is reported in
<a class="bz_bug_link
bz_status_NEW "
title="NEW - [InstCombiner] fatal error: error in backend: Instruction Combining seems stuck in an infinite loop"
href="show_bug.cgi?id=47788">https://bugs.llvm.org/show_bug.cgi?id=47788</a>
and
<a class="bz_bug_link
bz_status_NEW "
title="NEW - ICE on x86_64-linux-gnu at `-O3` (Instruction Combining seems stuck in an infinite loop after 100 iterations.)"
href="show_bug.cgi?id=47344">https://bugs.llvm.org/show_bug.cgi?id=47344</a>
or not.
Thanks,
Haoxin
</pre>
</div>
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