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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missed optimization with int overflow"
href="https://bugs.llvm.org/show_bug.cgi?id=35725">35725</a>
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<tr>
<th>Summary</th>
<td>Missed optimization with int overflow
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>zamazan4ik@tut.by
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>clang(trunk) with '-O3 -std=c++17 -ffast-math' for this:
#include <limits>
int test(int x)
{
if(x == std::numeric_limits<int>::max())
{
return x+1;
}
return 42;
}
generates this:
test(int): # @test(int)
lea ecx, [rdi + 1]
cmp edi, 2147483647
mov eax, 42
cmove eax, ecx
ret
But branch with condition is UB, so you can just delete it and simply return
42.</pre>
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