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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [X86][SSE] Use re-materializable -1 for vector increment/decrement"
href="https://bugs.llvm.org/show_bug.cgi?id=33483">33483</a>
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<th>Summary</th>
<td>[X86][SSE] Use re-materializable -1 for vector increment/decrement
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</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>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, peter@cordes.ca, spatel+llvm@rotateright.com
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<p>
<div>
<pre>define <4 x i32> @inc(<4 x i32>) {
%2 = add <4 x i32> %0, <i32 1, i32 1, i32 1, i32 1>
ret <4 x i32> %2
}
define <4 x i32> @dec(<4 x i32>) {
%2 = sub <4 x i32> %0, <i32 1, i32 1, i32 1, i32 1>
ret <4 x i32> %2
}
These currently do a constant load:
inc:
vpaddd .LCPI0_0(%rip), %xmm0, %xmm0
retq
dec:
vpsubd .LCPI1_0(%rip), %xmm0, %xmm0
retq
But they could do this using the re-materializable -1 value instead:
inc:
vcmpeqd %xmm1, %xmm1, %xmm1
vpsubd %xmm1, %xmm0, %xmm0
retq
dec:
vcmpeqd %xmm1, %xmm1, %xmm1
vpaddd %xmm1, %xmm0, %xmm0
retq</pre>
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