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From: Konstantin Ananyev <konstantin.ananyev@huawei.com>
To: Stephen Hemminger <stephen@networkplumber.org>,
	"Varghese, Vipin" <vipin.varghese@amd.com>
Cc: "ferruh.yigit@amd.com" <ferruh.yigit@amd.com>,
	"bruce.richardson@intel.com" <bruce.richardson@intel.com>,
	"konstantin.v.ananyev@yandex.ru" <konstantin.v.ananyev@yandex.ru>,
	"aman.deep.singh@intel.com" <aman.deep.singh@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Subject: RE: [PATCH v2 1/3] app/testpmd: add register keyword
Date: Tue, 3 Sep 2024 11:52:54 +0000	[thread overview]
Message-ID: <0ae233fb72ce49cea5186e1f924db76b@huawei.com> (raw)
In-Reply-To: <20240827103924.1d1d2711@hermes.local>



> > >
> > >> diff --git a/app/test-pmd/macswap_sse.h b/app/test-pmd/macswap_sse.h
> > >> index 223f87a539..29088843b7 100644
> > >> --- a/app/test-pmd/macswap_sse.h
> > >> +++ b/app/test-pmd/macswap_sse.h
> > >> @@ -16,13 +16,13 @@ do_macswap(struct rte_mbuf *pkts[], uint16_t nb,
> > >>        uint64_t ol_flags;
> > >>        int i;
> > >>        int r;
> > >> -     __m128i addr0, addr1, addr2, addr3;
> > >> +     register __m128i addr0, addr1, addr2, addr3;
> > > Some compilers treat register as a no-op. Are you sure? Did you check with godbolt.
> >
> > Thank you Stephen, I have tested the code changes on Linux using GCC and
> > Clang compiler.
> >
> > In both cases in Linux environment, we have seen the the values loaded
> > onto register `xmm`.
> >
> > ```
> > registerconst__m128i shfl_msk = _mm_set_epi8(15, 14, 13, 12, 5, 4, 3, 2,
> > 1, 0, 11, 10, 9, 8, 7, 6);
> > vmovdqaxmm0, xmmwordptr[rip+ .LCPI0_0]

Yep, that what I would probably expect: one time load before the loop starts, right?
Curious  what exactly it would generate then if 'register' keyword is missed?
BTW, on my box,  gcc-11  with '-O3 -msse4.2 ...'  I am seeing expected behavior without 'register' keyword.
Is it some particular compiler version that misbehaves?
 
> >
> > ```
> >
> > Both cases we have performance improvement.
> >
> >
> > Can you please help us understand if we have missed out something?
> 
> Ok, not sure why compiler would not decide to already use a register here?

  parent reply	other threads:[~2024-09-03 11:52 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-07-16  6:37 [PATCH] app/testpmd: improve sse based macswap Vipin Varghese
2024-07-23 16:45 ` Ferruh Yigit
2024-07-23 17:12   ` Bruce Richardson
2024-07-25 12:47     ` Varghese, Vipin
2024-07-25 12:52       ` Bruce Richardson
2024-08-21 14:38 ` [PATCH v2 0/3] " Vipin Varghese
2024-08-21 14:38   ` [PATCH v2 1/3] app/testpmd: add register keyword Vipin Varghese
2024-08-21 14:55     ` Stephen Hemminger
2024-08-27 15:32       ` Varghese, Vipin
2024-08-27 17:39         ` Stephen Hemminger
2024-08-29  8:14           ` Varghese, Vipin
2024-09-03 11:52           ` Konstantin Ananyev [this message]
2024-09-06 13:02             ` Varghese, Vipin
2024-10-04  5:04               ` Ferruh Yigit
2024-08-21 14:38   ` [PATCH v2 2/3] app/testpmd: move offload update Vipin Varghese
2024-08-21 14:38   ` [PATCH v2 3/3] app/testpmd: interleave SSE SIMD Vipin Varghese
2024-10-04  5:08   ` [PATCH v2 0/3] app/testpmd: improve sse based macswap Ferruh Yigit
2024-10-08  1:12     ` Ferruh Yigit

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