<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [x86] load/splat scalar constants for use with scalar FP logic ops?"
href="https://bugs.llvm.org/show_bug.cgi?id=40905">40905</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[x86] load/splat scalar constants for use with scalar FP logic ops?
</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>All
</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: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>spatel+llvm@rotateright.com
</td>
</tr>
<tr>
<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
</td>
</tr></table>
<p>
<div>
<pre>Seen in:
<a href="https://reviews.llvm.org/D58282">https://reviews.llvm.org/D58282</a>
declare <4 x double> @llvm.copysign.v4f64(<4 x double>, <4 x double>)
define double @copysign_v4f64(<4 x double> %x, <4 x double> %y) nounwind {
%v = call <4 x double> @llvm.copysign.v4f64(<4 x double> %x, <4 x double> %y)
%r = extractelement <4 x double> %v, i32 0
ret double %r
}
We convert this to a scalar op, but the x86 FP logic ops only allow load
folding with vector constants so:
$ ./llc -o - -mattr=avx copysign.ll
LCPI0_0:
.quad -9223372036854775808 ## double -0
.quad -9223372036854775808 ## double -0
LCPI0_1:
.quad 9223372036854775807 ## double NaN
.quad 9223372036854775807 ## double NaN
.section __TEXT,__text,regular,pure_instructions
.globl _copysign_v4f64
.p2align 4, 0x90
_copysign_v4f64:
vandps LCPI0_0(%rip), %xmm1, %xmm1
vandps LCPI0_1(%rip), %xmm0, %xmm0
vorps %xmm1, %xmm0, %xmm0
vzeroupper
retq
----------------------------------------------------------------------
Should we broadcast scalar constants instead? The answer may depend on whether
we are optimizing for size and/or subtarget.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>