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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang produces incorrect code with -O2 and higher"
href="https://bugs.llvm.org/show_bug.cgi?id=37748">37748</a>
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<th>Summary</th>
<td>Clang produces incorrect code with -O2 and higher
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>LLVM Codegen
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>Vsevolod.Livinskij@frtk.ru
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<pre>Created <span class=""><a href="attachment.cgi?id=20413" name="attach_20413" title="Reproducer.">attachment 20413</a> <a href="attachment.cgi?id=20413&action=edit" title="Reproducer.">[details]</a></span>
Reproducer.
Clang miscompiles with -O2 and higher.
opt-bisect-limit points to CodeGen Prepare on function
Reproducer:
<span class="quote">>$ cat func.c</span >
extern long a;
extern long b;
extern unsigned short c;
extern long d;
extern short e;
void foo() {
a = (short)(e | (c & -32692));
if (c / d)
b = (e | (c & -32692)) > 0;
}
<span class="quote">>$ cat driver.c</span >
#include <stdio.h>
long a, b;
unsigned short c = 43589;
long d = 3;
short e;
void foo();
int main() {
foo();
printf("%ld\n", a);
}
Error:
<span class="quote">>$ clang driver.c func.c ; ./a.out</span >
-32700
<span class="quote">>$ clang -O2 driver.c func.c ; ./a.out</span >
32836
LLVM version:
clang version 7.0.0 (trunk 334268)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /llvm/bin-trunk/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.2
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.5
Selected GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.8.5
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64</pre>
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