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Re: [Qemu-devel] [RFC][PATCH 4/9] buffer_is_zero: use vector optimizatio
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [RFC][PATCH 4/9] buffer_is_zero: use vector optimizations if possible |
Date: |
Tue, 12 Mar 2013 10:01:45 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130219 Thunderbird/17.0.3 |
On 03/12/2013 09:50 AM, Peter Lieven wrote:
> performance gain on SSE2 is approx. 20-25%. altivec
> is not tested. performance for unsigned long arithmetic
> is unchanged.
>
> Signed-off-by: Peter Lieven <address@hidden>
> ---
> util/cutils.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/util/cutils.c b/util/cutils.c
> index a09d8e8..23f0cd6 100644
> --- a/util/cutils.c
> +++ b/util/cutils.c
> @@ -186,6 +186,11 @@ bool buffer_is_zero(const void *buf, size_t len)
> * latency.
> */
>
> + if (((uintptr_t) buf) % sizeof(VECTYPE) == 0
> + && len % 8*sizeof(VECTYPE) == 0) {
Space around binary operators. Use CHAR_BITS instead of a magic number
8. Also, did you mean:
len % (CHAR_BITS * sizeof(VECTYPE))
instead of what you wrote as '(len % 8) * sizeof(VECTYPE)'?
> + return buffer_find_nonzero_offset(buf, len)==len;
> + }
> +
> size_t i;
> long d0, d1, d2, d3;
> const long * const data = buf;
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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