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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Delinearization fails and produces invariant access function for variant access"
href="https://llvm.org/bugs/show_bug.cgi?id=27013">27013</a>
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<th>Summary</th>
<td>Delinearization fails and produces invariant access function for variant access
</td>
</tr>
<tr>
<th>Product</th>
<td>Polly
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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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>
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<th>Component</th>
<td>Other
</td>
</tr>
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<th>Assignee</th>
<td>polly-dev@googlegroups.com
</td>
</tr>
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<th>Reporter</th>
<td>doerfert@cs.uni-saarland.de
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</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=16064" name="attach_16064" title="IR testcase">attachment 16064</a> <a href="attachment.cgi?id=16064&action=edit" title="IR testcase">[details]</a></span>
IR testcase
For the C code:
for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
lastDC = lastblockrow[h_samp_factor - 1][0];
for (bi = 0; bi < h_samp_factor; bi++) {
thisblockrow[bi][0] = lastDC;
}
thisblockrow += h_samp_factor; /* advance to next MCU in row */
lastblockrow += h_samp_factor;
}
in
MultiSource/Benchmarks/mediabench/jpeg/jpeg-6a/jccoefct.c
we generate variant multidimensional accesses even though there are none.
This causes us to hoist "lastblockrow[h_samp_factor - 1][0]", thus
mis-compiling the code. The problem seems to be the PHI nodes that change the
pointers for "thisblockrow" and "lastblockrow" break some delinarization
process.
NOTE: You need to allow unsigned comparisons (or change the unsigned comparison
in the code)!</pre>
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