<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 - [AArch64] improve codegen for -abs(x)"
href="https://bugs.llvm.org/show_bug.cgi?id=52216">52216</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[AArch64] improve codegen for -abs(x)
</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: AArch64
</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>arnaud.degrandmaison@arm.com, llvm-bugs@lists.llvm.org, smithp352@googlemail.com, Ties.Stuij@arm.com
</td>
</tr></table>
<p>
<div>
<pre>Splitting off from what was originally in <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [X86] Failure to flip cmov cc for -abs(x)"
href="show_bug.cgi?id=50991">bug 50991</a> (but that was fixed for x86
only):
define i32 @nabs32(i32 %0) {
%2 = tail call i32 @llvm.abs.i32(i32 %0, i1 true)
%3 = sub nsw i32 0, %2
ret i32 %3
}
define i64 @nabs64(i64 %0) {
%2 = tail call i64 @llvm.abs.i64(i64 %0, i1 true) #3
%3 = sub nsw i64 0, %2
ret i64 %3
}
declare i32 @llvm.abs.i32(i32, i1 immarg)
declare i64 @llvm.abs.i64(i64, i1 immarg)
----------------------------------------------------------------------------
% llc -o - nabs.ll -mtriple=aarch64
nabs32: // @nabs32
cmp w0, #0
cneg w8, w0, mi
neg w0, w8
ret
nabs64: // @nabs64
cmp x0, #0
cneg x8, x0, mi
neg x0, x8
ret
----------------------------------------------------------------------------
gcc does better on these:
<a href="https://godbolt.org/z/GbYha3Kso">https://godbolt.org/z/GbYha3Kso</a>
...but note that i8 and possibly i16 are better as-is with clang.</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>