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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 - Codegen regression with sign extensions"
href="https://bugs.llvm.org/show_bug.cgi?id=50126">50126</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Codegen regression with sign extensions
</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>
<tr>
<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: ARM
</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, smithp352@googlemail.com, Ties.Stuij@arm.com
</td>
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<p>
<div>
<pre>struct s {
short x, y;
};
struct s rot90(struct s p)
{
return (struct s) { -p.y, p.x };
}
struct s rot270(struct s p)
{
return (struct s) { p.y, -p.x };
}
Trunk:
rot90: // @rot90
neg w8, w0, lsr #16
lsl w0, w0, #16
bfxil x0, x8, #0, #16
ret
rot270: // @rot270
neg w8, w0, lsl #16
bfxil x8, x0, #16, #16
mov x0, x8
ret
rot90: // @rot90
neg w8, w0, lsr #16
bfi w8, w0, #16, #16
mov x0, x8
ret
rot270: // @rot270
ubfx x8, x0, #16, #16
sub w0, w8, w0, lsl #16
ret
Maybe ideal codegen?:
rot90:
mov w1, w0
neg w0, w1, asr 16
bfi w0, w1, 16, 16
ret
rot270:
neg w1, w0
extr w0, w1, w0, 16
ret
See it live:
<a href="https://gcc.godbolt.org/z/4c4ds58v6">https://gcc.godbolt.org/z/4c4ds58v6</a></pre>
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