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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 - Better switch lowering using and + sete"
href="https://bugs.llvm.org/show_bug.cgi?id=39116">39116</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Better switch lowering using and + sete
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</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>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>bool switch_ob_one_two_cases(int x) {
switch(x) {
case 0:
case 2:
return true;
default:
return false;
}
}
Clang:
switch_ob_one_two_cases(int):
mov al, 1
or edi, 2
cmp edi, 2
jne .LBB0_1
ret
.LBB0_1:
xor eax, eax
ret
GCC can emit nice code:
switch_ob_one_two_cases(int):
and edi, -3
sete al
ret
bool switch_ob_one_two_cases2(int x) {
switch(x) {
case 7:
case 11:
return true;
default:
return false;
}
}
GCC:
switch_ob_one_two_cases2(int):
sub edi, 7
and edi, -5
sete al
ret</pre>
</div>
</p>
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