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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [InstructionCombiner (?)] WRONG CODE involving @llvm.vector.reduce.xor"
href="https://bugs.llvm.org/show_bug.cgi?id=50145">50145</a>
</td>
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<th>Summary</th>
<td>[InstructionCombiner (?)] WRONG CODE involving @llvm.vector.reduce.xor
</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>
<tr>
<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>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>paulsson@linux.vnet.ibm.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=24806" name="attach_24806" title="reduced testcase">attachment 24806</a> <a href="attachment.cgi?id=24806&action=edit" title="reduced testcase">[details]</a></span>
reduced testcase
The attached program should print '0' but currently it prints '119' on
SystemZ...
A bisect leads to 79b1b4a "[Vectorizers][TTI] remove option to bypass creation
of vector reduction intrinsics". The only difference in the IR after SLP is
then:
%rdx.shuf = shufflevector <4 x i8> %32, <4 x i8> poison, <4 x i32> <i32 2, i32
3, i32 undef, i32 undef>
%bin.rdx = xor <4 x i8> %32, %rdx.shuf
%rdx.shuf11 = shufflevector <4 x i8> %bin.rdx, <4 x i8> poison, <4 x i32> <i32
1, i32 undef, i32 undef, i32 undef>
%bin.rdx12 = xor <4 x i8> %bin.rdx, %rdx.shuf11
%47 = extractelement <4 x i8> %bin.rdx12, i32 0
<>
%47 = call i8 @llvm.vector.reduce.xor.v4i8(<4 x i8> %32)
This then later gets different treatment of InstCombiner. With the shuffles,
the store to @d dissapears, but with the intrinsic it seems some poison value
ends up being stored...
clang -march=z13 -O3 wrong0.i -o a.out -w ; ./a.out</pre>
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