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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - missed optimization for dead code elimination at -O3 (vs. -O1)"
href="https://bugs.llvm.org/show_bug.cgi?id=51138">51138</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>missed optimization for dead code elimination at -O3 (vs. -O1)
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</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>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>theodoros.theodoridis@inf.ethz.ch
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<div>
<pre>$./bin/clang -v
clang version 13.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
96d8f2a1e0842b83b319a8daf3cc82dd5e1350fa)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /dev/shm/llvm-project/build/./bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
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/10
Candidate multilib: .;@m64
Selected multilib: .;@m64
$cat test.c
extern void foo(void);
short a(short b, int c) { return c >= 32 || b >> c ? b : b << c; }
int d;
int main() {
int e = 1;
d || (e = -2);
if (!a(e, 15)) {
foo();
for (; e; e--)
;
}
return 0;
}
$./bin/clang -O1 test.c -S -o O1.s
$./bin/clang -O3 test.c -S -o O3.s
$grep foo O1.s
$grep foo O3.s
callq foo</pre>
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