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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW " title="NEW --- - range metadata can be ignored" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D23848&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=1aL1w7j2gUIbNh9z_5wZ96BM3ELWH2sPAg-4G-6hG7k&s=Rl3z73gSfRP6pYg1dDJSMbm2OEk5m0Cil10mNSA6zdc&e=">23848</a>
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<th>Summary</th>
<td>range metadata can be ignored
</td>
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<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
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<th>Version</th>
<td>trunk
</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>
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<th>Severity</th>
<td>normal
</td>
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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
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<th>Reporter</th>
<td>pitrou@free.fr
</td>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=14474" name="attach_14474" title="IR file reproducing the issue">attachment 14474</a> <a href="attachment.cgi?id=14474&action=edit" title="IR file reproducing the issue">[details]</a></span>
IR file reproducing the issue
If you take the attached IR file and try to optimize it using "opt -O3 -S
shape_is_pos.ll", you will get the following output (i.e. LLVM doesn't realize
the condition is always true):
define i1 @is_positive(i64 %arg) #0 {
entry:
%result = icmp sgt i64 %arg, -1
ret i1 %result
}
OTOH if you uncomment the two lines were llvm.assume is called, you get the
following (the return code is properly optimized to true):
define i1 @is_positive(i64 %arg) #0 {
entry:
%is_pos = icmp sgt i64 %arg, -1
tail call void @llvm.assume(i1 %is_pos)
ret i1 true
}
(this is something I stumbled on, in a more complicated form, in Numba;
unfortunately llvm.assume() can also pessimize some of our benchmarks)</pre>
</div>
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