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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Miscompile with -opt -loop-vectorize after 8871a4b4cab8"
href="https://bugs.llvm.org/show_bug.cgi?id=48832">48832</a>
</td>
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<tr>
<th>Summary</th>
<td>Miscompile with -opt -loop-vectorize after 8871a4b4cab8
</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>
<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>Loop Optimizer
</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>
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<pre>Created <span class=""><a href="attachment.cgi?id=24405" name="attach_24405" title="bbi-51947.ll reproducer">attachment 24405</a> <a href="attachment.cgi?id=24405&action=edit" title="bbi-51947.ll reproducer">[details]</a></span>
bbi-51947.ll reproducer
With
opt -mtriple=s390x-unknown-linux -mcpu=z13 -loop-vectorize -S -o -
bbi-51947.ll
I get a
store <4 x i32> poison, <4 x i32>* %6, align 1
which I htink is incorrect.
This starts happening with 8871a4b4cab8:
[Constant] Update ConstantVector::get to return poison if all input elems
are poison
The diff was reviewed at D93994
Before the patch I got
store <4 x i32> zeroinitializer, <4 x i32>* %6, align 1
The input is
%arrayt = type [64 x i32]
@v_146 = external global %arrayt, align 1
define void @foo() {
entry:
br label %for.cond
for.cond: ; preds = %cond.end, %entry
%storemerge = phi i16 [ 0, %entry ], [ %inc, %cond.end ]
%cmp = icmp slt i16 %storemerge, 15
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
br i1 true, label %cond.false, label %land.rhs
land.rhs: ; preds = %for.body
br i1 poison, label %cond.end, label %cond.false
cond.false: ; preds = %for.body,
%land.rhs
br label %cond.end
cond.end: ; preds = %land.rhs,
%cond.false
%cond = phi i32 [ 0, %cond.false ], [ 1, %land.rhs ]
%arrayidx = getelementptr inbounds %arrayt, %arrayt* @v_146, i16 0, i16
%storemerge
store i32 %cond, i32* %arrayidx, align 1
%inc = add nsw i16 %storemerge, 1
br label %for.cond
for.end: ; preds = %for.cond
ret void
}
Note the
for.body: ; preds = %for.cond
br i1 true, label %cond.false, label %land.rhs
land.rhs: ; preds = %for.body
br i1 poison, label %cond.end, label %cond.false
%land.rhs is dead due to the "br i1 true" branch, but I think it still is
involved somehow in making the stored value poison with this patch.</pre>
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