<html>
<head>
<base href="http://llvm.org/bugs/" />
</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 --- - missed opportunity to use wider (AVX2) vectors"
href="http://llvm.org/bugs/show_bug.cgi?id=17170">17170</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>missed opportunity to use wider (AVX2) vectors
</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>normal
</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>kkhoo@perfwizard.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following code sequence is correctly identified as an opportunity to use a
parallel (AVX) addition operation, but it could have been optimized further by
using 32-byte (8-integer) vector instructions rather than 16-byte (4-integer)
vector instructions:
$ ./clang -v
clang version 3.4 (trunk 189776)
Target: x86_64-apple-darwin11.4.2
Thread model: posix
$ cat paddd.c
void foo(int *restrict x, int *restrict y, int *restrict z) {
int i;
for (i=0; i<8; i++) {
z[i] = x[i] + y[i];
}
}
$ ./clang -S -std=c99 -O3 -funroll-loops -fomit-frame-pointer -march=core-avx2
-o /dev/stdout paddd.c
.section __TEXT,__text,regular,pure_instructions
.globl _foo
.align 4, 0x90
_foo: ## @foo
.cfi_startproc
## BB#0: ## %entry
vmovdqu (%rdi), %xmm0
vpaddd (%rsi), %xmm0, %xmm0
vmovdqu %xmm0, (%rdx)
vmovdqu 16(%rdi), %xmm0
vpaddd 16(%rsi), %xmm0, %xmm0
vmovdqu %xmm0, 16(%rdx)
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>