<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 - Missing optimisation: Type conversion not vectorised in simple additive reduction"
href="https://bugs.llvm.org/show_bug.cgi?id=32077">32077</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missing optimisation: Type conversion not vectorised in simple additive reduction
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</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>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>drraph@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Consider:
double f(double x[]) {
float p = 1.0;
for (int i = 0; i < 16; i++)
p += x[i];
return p;
}
clang/llvm with -O3 -march=core-avx2 -ffast-math gives:
.LCPI0_0:
.quad 4607182418800017408 # double 1
f: # @f
vmovsd xmm0, qword ptr [rdi] # xmm0 = mem[0],zero
vaddsd xmm0, xmm0, qword ptr [rip + .LCPI0_0]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 8]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 16]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 24]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 32]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 40]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 48]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 56]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 64]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 72]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 80]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 88]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 96]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 104]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 112]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
vaddsd xmm0, xmm0, qword ptr [rdi + 120]
vcvtsd2ss xmm0, xmm0, xmm0
vcvtss2sd xmm0, xmm0, xmm0
ret
However more efficient would be:
f:
vcvtpd2ps xmm0, YMMWORD PTR [rdi] #4.5
vcvtpd2ps xmm1, YMMWORD PTR [32+rdi] #4.5
vcvtpd2ps xmm2, YMMWORD PTR [64+rdi] #4.5
vcvtpd2ps xmm3, YMMWORD PTR [96+rdi] #4.5
vaddps xmm4, xmm0, xmm1 #2.11
vaddps xmm5, xmm2, xmm3 #2.11
vaddps xmm6, xmm4, xmm5 #2.11
vmovhlps xmm7, xmm6, xmm6 #2.11
vaddps xmm8, xmm6, xmm7 #2.11
vshufps xmm9, xmm8, xmm8, 245 #2.11
vaddss xmm10, xmm8, xmm9 #2.11
vaddss xmm0, xmm10, DWORD PTR .L_2il0floatpacket.0[rip] #2.11
vcvtss2sd xmm0, xmm0, xmm0 #5.10
vzeroupper #5.10
ret #5.10
.L_2il0floatpacket.0:
.long 0x3f800000</pre>
</div>
</p>
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