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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Opt incorrectly optimizes pr41454 from gcc testsuite"
href="http://llvm.org/bugs/show_bug.cgi?id=18927">18927</a>
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<th>Summary</th>
<td>Opt incorrectly optimizes pr41454 from gcc testsuite
</td>
</tr>
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<th>Product</th>
<td>tools
</td>
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<th>Version</th>
<td>3.4
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>opt
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>ihusar@fit.vutbr.cz
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=12099" name="attach_12099" title="test c file">attachment 12099</a> <a href="attachment.cgi?id=12099&action=edit" title="test c file">[details]</a></span>
test c file
The code in attachment
#define OFFS 12
int main ()
{
int BM_tab2[OFFS];
int *BM_tab = BM_tab2;
int *BM_tab_base;
BM_tab_base = BM_tab;
BM_tab += OFFS;
while (BM_tab_base != BM_tab)
{
*--BM_tab = 6;
*--BM_tab = 6;
}
if (BM_tab2[0] != 6)
abort ();
return 0;
}
get incorrectly optimized by opt -O3 to
; Function Attrs: nounwind uwtable
define i32 @main() #0 {
if.then:
call void @abort() #2
unreachable
}
Strange is that when I change OFFS to e.g. 2, 4, 6, 8, 10 then it works
correctly. Values 12, 14, 16, ... cause this test be optimized only to the
abort call. With gcc this test works fine.
I used clang and opt with -O3:
clang version 3.4 (tags/RELEASE_34/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix</pre>
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