<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 - Regression: LLVM9 trunk misoptimization of llvm.x86.sse.movmsk.ps for i586-unknown-linux-gnu"
href="https://bugs.llvm.org/show_bug.cgi?id=42870">42870</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Regression: LLVM9 trunk misoptimization of llvm.x86.sse.movmsk.ps for i586-unknown-linux-gnu
</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>release blocker
</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>gonzalobg88@gmail.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>LLVM8 opt and LLVM9 (trunk) opt, do optimize llvm.x86.sse.movmsk.ps
differently. LLVM8 leaves it as is, while LLVM9 transforms it to (see godbolt:
<a href="https://godbolt.org/z/35BloZ">https://godbolt.org/z/35BloZ</a>):
define i32 @_ZN7example15_mm_movemask_ps17h9d7ca884d8f840c4E(<4 x float>*
noalias nocapture readonly dereferenceable(16) %a) unnamed_addr #0 {
start:
%0 = bitcast <4 x float>* %a to <4 x i32>*
%1 = load <4 x i32>, <4 x i32>* %0, align 16
%2 = icmp slt <4 x i32> %1, zeroinitializer
%3 = bitcast <4 x i1> %2 to i4
%4 = zext i4 %3 to i32
ret i32 %4
}
As a consequence, LLVM8 produces the following machine code for mm_movemask_ps
on i586-unknown-linux-gnu:
example::_mm_movemask_ps: # @example::_mm_movemask_ps
mov eax, dword ptr [esp + 4]
movaps xmm0, xmmword ptr [eax]
movmskps eax, xmm0
ret
while LLVM9 produces:
example::_mm_movemask_ps: # @example::_mm_movemask_ps
mov eax, dword ptr [esp + 4]
cmp dword ptr [eax], 0
sets cl
cmp dword ptr [eax + 4], 0
sets dl
add dl, dl
or dl, cl
cmp dword ptr [eax + 8], 0
sets cl
cmp dword ptr [eax + 12], 0
sets al
add al, al
or al, cl
shl al, 2
or al, dl
movzx eax, al
ret</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>