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From: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
To: Richard Henderson <rth@twiddle.net>
Cc: qemu-devel@nongnu.org, aurelien@aurel32.net, agraf@suse.de
Subject: Re: [Qemu-devel] [PATCH 5/7] tcg-i386: Implement deposit operation.
Date: Tue, 25 Jan 2011 17:48:16 +0100	[thread overview]
Message-ID: <20110125164816.GA23569@laped.lan> (raw)
In-Reply-To: <4D3EF6C1.3080502@twiddle.net>

On Tue, Jan 25, 2011 at 08:13:53AM -0800, Richard Henderson wrote:
> On 01/25/2011 04:27 AM, Edgar E. Iglesias wrote:
> > I've tested this patch a bit and got mixed results. I tested with patched
> > CRIS and MicroBlaze translators. The patch works OK (it doesn't break
> > anything) for the usecases I had but I saw a bit of a slowdown with
> > MicroBlaze (compare to not using deposit at all).
> > 
> > I suspect that the fast 8 and 16 bit x86 deposits are giving me a slight
> > speedup with CRIS. But MicroBlaze uses one bit fields into bit 2 and
> > 31. Those seem to be slower with deposit than with other tcg sequences.
> > 
> > I would have guessed that at worst, this patch would be equally fast
> > as any TCG sequence. Am I missing something?
> 
> With or without the i386 tcg-target.c changes?
> 
> If without, then I'm stumped, since it looks like identical tcg ops
> being emitted.

It's with the tcg-target patch.

> It with, then perhaps SHLD is slower than I thought.  I see that GCC
> lists this insn as "vector decoded" for AMD cores, as opposed to
> "direct decoded".  If this insn is indeed microcoded on some hosts
> then maybe the i386 tcg-target patch isn't such a great idea.

OK, I see. Maybe we should try to emit an insn sequence more similar
to what tcg was emitting (for the non 8 & 16-bit deposits)?
That ought too at least give similar results as before for those and
give us a speedup for the byte and word moves.

> That said, there are still other tcg targets which support this 
> operation directly.  I would be shocked if you measured a slowdown
> with these changes on a ppc host, for instance.

Yep, agreed.

Cheers

  reply	other threads:[~2011-01-25 16:49 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-11  3:23 [Qemu-devel] [PATCH 0/7] Define "deposit" tcg operation, v2 Richard Henderson
2011-01-11  3:23 ` [Qemu-devel] [PATCH 1/7] tcg: Define "deposit" as an optional operation Richard Henderson
2011-01-11 23:45   ` Aurelien Jarno
2011-01-12 11:00   ` Edgar E. Iglesias
2011-01-11  3:23 ` [Qemu-devel] [PATCH 2/7] tcg-ppc: Implement deposit operation Richard Henderson
2011-01-11 12:40   ` [Qemu-devel] " malc
2011-01-11 16:32     ` Richard Henderson
2011-01-11 19:11       ` malc
2011-01-11  3:23 ` [Qemu-devel] [PATCH 3/7] tcg-hppa: " Richard Henderson
2011-01-11  3:23 ` [Qemu-devel] [PATCH 4/7] tcg-ia64: " Richard Henderson
2011-01-11  3:23 ` [Qemu-devel] [PATCH 5/7] tcg-i386: " Richard Henderson
2011-01-25 12:27   ` Edgar E. Iglesias
2011-01-25 16:13     ` Richard Henderson
2011-01-25 16:48       ` Edgar E. Iglesias [this message]
2011-01-25 22:07         ` Richard Henderson
2011-01-26  8:53           ` Edgar E. Iglesias
2011-01-26  9:23             ` Alexander Graf
2011-01-26 15:50               ` Richard Henderson
2011-01-26 16:00                 ` Alexander Graf
2011-01-26 16:34                   ` Avi Kivity
2011-01-26 16:40                   ` Richard Henderson
2011-01-26 16:50                     ` Alexander Graf
2011-01-26 18:21                       ` Richard Henderson
2011-01-26 18:27                         ` Alexander Graf
2011-01-26 18:55                           ` Richard Henderson
2011-01-26 19:01                             ` Alexander Graf
2011-01-26 19:05                               ` Richard Henderson
2011-01-26 19:09                                 ` Alexander Graf
2011-01-26 19:19                                   ` Richard Henderson
2011-01-26 19:27                                     ` Alexander Graf
2011-01-31  8:33     ` Aurelien Jarno
2011-02-08 18:05       ` Richard Henderson
2011-02-09  7:41         ` [Qemu-devel] " Paolo Bonzini
2011-02-09 17:24           ` Blue Swirl
2011-01-11  3:23 ` [Qemu-devel] [PATCH 6/7] target-i386: Use " Richard Henderson
2011-01-12 11:01   ` Edgar E. Iglesias
2011-01-20 11:06   ` Aurelien Jarno
2011-01-11  3:23 ` [Qemu-devel] [PATCH 7/7] target-ppc: " Richard Henderson
2011-01-11 23:45 ` [Qemu-devel] [PATCH 0/7] Define "deposit" tcg operation, v2 Aurelien Jarno
2011-01-20 11:31 ` Edgar E. Iglesias
  -- strict thread matches above, loose matches on Subject: below --
2011-01-07 22:42 [Qemu-devel] [PATCH 0/7] Define "deposit" tcg operation Richard Henderson
2011-01-07 22:43 ` [Qemu-devel] [PATCH 5/7] tcg-i386: Implement deposit operation Richard Henderson

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