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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Range does not handle `add` and `ugt` comparison well"
href="https://bugs.llvm.org/show_bug.cgi?id=35069">35069</a>
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<th>Summary</th>
<td>Range does not handle `add` and `ugt` comparison well
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>5.0
</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>Scalar Optimizations
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>yyc1992@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Reproduced with following IR.
```
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define void @f(i64*) {
%2 = load i64, i64* %0, align 8, !range !0
%3 = add i64 %2, -1
%4 = icmp ugt i64 %3, 1000
br i1 %4, label %L1, label %L2
L1:
tail call void @g()
unreachable
L2:
ret void
}
declare void @g()
!0 = !{i64 2, i64 100}
```
I believe that the function should be optmized to `ret void` since the `icmp`
should always be `false` for the specified range. However, `opt` with
`-instcombine`, `-instsimplify` or just `-O3` does nothing to the `icmp` or the
branch.
Removing the `add` (and make `icmp` take the load value directly) works as
expected as well as replacing the `ugt` with `sgt` even though it shouldn't
make a difference in the value range....</pre>
</div>
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