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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - LoopVectorizer triggers "Instruction does not dominate all uses!" after r326079"
href="https://bugs.llvm.org/show_bug.cgi?id=37248">37248</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>LoopVectorizer triggers "Instruction does not dominate all uses!" after r326079
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</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>mikael.holmen@ericsson.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=20226" name="attach_20226" title="reproducer">attachment 20226</a> <a href="attachment.cgi?id=20226&action=edit" title="reproducer">[details]</a></span>
reproducer
Running
opt -loop-vectorize -S -o - tr15930.ll
with this commit gives:
Instruction does not dominate all uses!
%25 = trunc i32 %offset.idx16 to i16
%broadcast.splatinsert17 = insertelement <4 x i16> undef, i16 %25, i32 0
LLVM ERROR: Broken function found, compilation aborted!
Looking at the output after the loop vectorizer we get
*** IR Dump After Loop Vectorization ***
define void @f1() {
entry:
br i1 false, label %scalar.ph, label %vector.scevcheck
vector.scevcheck: ; preds = %entry
%mul = call { i16, i1 } @llvm.umul.with.overflow.i16(i16 1, i16 undef)
%mul.result = extractvalue { i16, i1 } %mul, 0
%mul.overflow = extractvalue { i16, i1 } %mul, 1
%0 = add i16 undef, %mul.result
%1 = sub i16 undef, %mul.result
%2 = icmp sgt i16 %1, undef
%3 = icmp slt i16 %0, undef
%4 = select i1 true, i1 %2, i1 %3
%5 = or i1 %4, %mul.overflow
%6 = or i1 false, %5
br i1 %6, label %scalar.ph, label %vector.ph
vector.ph: ; preds = %vector.scevcheck
%broadcast.splatinsert17 = insertelement <4 x i16> undef, i16 %25, i32 0
%broadcast.splat18 = shufflevector <4 x i16> %broadcast.splatinsert17, <4 x
i16> undef, <4 x i32> zeroinitializer
br label %vector.body
[...]
pred.load.continue15: ; preds = %pred.load.if14,
%pred.load.continue13
%24 = phi i32 [ undef, %pred.load.continue13 ], [ %23, %pred.load.if14 ]
%offset.idx16 = sub i32 undef, %index
%25 = trunc i32 %offset.idx16 to i16
If we follow the path
entry -> vector.scevcheck -> vector.ph
we see that the def of %25 in pred.load.continue15 doesn't dominate the use in
vector.ph.</pre>
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