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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - load from @i hoisted before store to @i by -speculative-execution"
href="https://bugs.llvm.org/show_bug.cgi?id=32964">32964</a>
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<th>Summary</th>
<td>load from @i hoisted before store to @i by -speculative-execution
</td>
</tr>
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<th>Product</th>
<td>new-bugs
</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>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>mikael.holmen@ericsson.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=18415" name="attach_18415" title="reproducer">attachment 18415</a> <a href="attachment.cgi?id=18415&action=edit" title="reproducer">[details]</a></span>
reproducer
opt -S -speculative-execution -o - spec.ll
In the input we have:
entry:
%0 = load i8, i8* @i
%tobool = icmp eq i8 %0, 0
br i1 %tobool, label %if.end, label %if.then
if.then: ; preds = %entry
store i8 0, i8* @i
%.pre = load i8, i8* @i
br label %if.end
and in the output we get:
entry:
%0 = load i8, i8* @i
%tobool = icmp eq i8 %0, 0
%.pre = load i8, i8* @i
br i1 %tobool, label %if.end, label %if.then
if.then: ; preds = %entry
store i8 0, i8* @i
br label %if.end
so
%.pre = load i8, i8* @i
has been moved before
store i8 0, i8* @i
and we'll load the old (wrong) value.
This started going wrong after commit
SpeculativeExecution: Stop using whitelist for costs
but I suppose that is because costs in general went down
with that patch so it triggers in more cases.
This seems very broken to me and I see these errors a lot in our out-of-tree
backend.</pre>
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