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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Merging GEP inbounds of GEP incorrectly preserves inbounds"
href="https://bugs.llvm.org/show_bug.cgi?id=44425">44425</a>
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<th>Summary</th>
<td>Merging GEP inbounds of GEP incorrectly preserves inbounds
</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>
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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>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>nikita.ppv@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>define i32* @test_gep2(i32* %base) {
%ptr1 = getelementptr i32, i32* %base, i64 4
%ptr2 = getelementptr inbounds i32, i32* %ptr1, i64 4
ret i32* %ptr2
}
opt -instcombine
define i32* @test_gep2(i32* %base) {
%ptr2 = getelementptr inbounds i32, i32* %base, i64 8
ret i32* %ptr2
}
I believe this this transform isn't correct, e.g. if the original %base was
pointing 4 elements before the start of an object.
This only happens in the case where the GEP is updated in-place.
Noticed this while looking into <a class="bz_bug_link
bz_status_NEW "
title="NEW - LLVM 10 regression in gep inbounds of zero-offset gep"
href="show_bug.cgi?id=44423">https://bugs.llvm.org/show_bug.cgi?id=44423</a>...</pre>
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</p>
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