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Re: [PATCH 09/10] i386: Replace assembly versions of e_log2f with generic e_log2f.c
- From: Szabolcs Nagy <szabolcs dot nagy at arm dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Cc: nd at arm dot com
- Date: Fri, 20 Oct 2017 15:55:16 +0100
- Subject: Re: [PATCH 09/10] i386: Replace assembly versions of e_log2f with generic e_log2f.c
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On 19/10/17 20:51, H.J. Lu wrote:
> On Thu, Oct 19, 2017 at 10:31 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> This patch replaces i386 assembly versions of e_log2f with generic
>> e_log2f.c. For workload-spec2017.wrf, on Nehalem, it improves
>> performance by:
>>
>> Before After Improvement
>> reciprocal-throughput 92.3845 30.8752 199%
>> latency 112.855 54.8645 105%
>>
>> On Skylake, it improves performance by:
>>
>> Before After Improvement
>> reciprocal-throughput 98.7488 22.7507 334%
>> latency 118.01 51.6083 128%
>
> On IvyBridge with --disable-multi-arch, it improves performance by:
>
> Before After Improvement
> reciprocal-throughput 106.635 28.8596 269%
> latency 129.888 56.9187 128%
>
is this comparing x87 c code with x87 asm?
or did the toolchain have -fpmath=sse?
i would not expect that much speedup on i386