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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 - Transform (1 << (x+1)) to (2 << x)"
href="https://bugs.llvm.org/show_bug.cgi?id=42631">42631</a>
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<th>Summary</th>
<td>Transform (1 << (x+1)) to (2 << x)
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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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
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<th>Reporter</th>
<td>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
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<pre>%a = add nuw i32 %x, 1
%r = shl i32 1, %a
=>
%r = shl i32 2, %x
Done: 1
Optimization is correct!
int v1(unsigned x) {
return (2 << x);
}
int v2(unsigned x) {
return (1 << (x+1));
}
v1: # @v1
mov ecx, edi
mov eax, 2
shl eax, cl
ret
v2: # @v2
lea ecx, [rdi + 1]
mov eax, 1
shl eax, cl
ret
Worth to do? Opinions?</pre>
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