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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missed optimization: int range info isn't used"
href="https://bugs.llvm.org/show_bug.cgi?id=43428">43428</a>
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<th>Summary</th>
<td>Missed optimization: int range info isn't used
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</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>Windows NT
</td>
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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>
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<th>Component</th>
<td>LLVM Codegen
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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</tr>
<tr>
<th>Reporter</th>
<td>zamazan4ik@tut.by
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>For the following code:
unsigned sample(unsigned m ){
if(m >= 10) return 42;
return m / 10;
}
clang(trunk) with '-O3' generates this:
sample(unsigned int): # @sample(unsigned int)
mov eax, 42
cmp edi, 9
ja .LBB0_2
mov ecx, edi
mov eax, 3435973837
imul rax, rcx
shr rax, 35
.LBB0_2:
ret
but gcc(trunk) with 'O3' optimizes more and generates this:
sample(unsigned int):
cmp edi, 10
sbb eax, eax
not eax
and eax, 42
ret
Godbolt playground: <a href="https://godbolt.org/z/Q-EaVW">https://godbolt.org/z/Q-EaVW</a></pre>
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