From: Eric Blake <eblake@redhat.com>
To: "Richard Henderson" <rth@twiddle.net>,
"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
qemu-devel@nongnu.org, "Aurelien Jarno" <aurelien@aurel32.net>,
"Nikunj A Dadhania" <nikunj@linux.vnet.ibm.com>,
"Markus Armbruster" <armbru@redhat.com>,
"Laurent Vivier" <lvivier@redhat.com>,
"Michael Tokarev" <mjt@tls.msk.ru>,
"Eduardo Habkost" <ehabkost@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 1/8] coccinelle: add a script to optimize tcg op using tcg_gen_extract()
Date: Wed, 10 May 2017 15:23:56 -0500 [thread overview]
Message-ID: <a2036e6f-5e10-ef4d-bf2b-f6704604bbbb@redhat.com> (raw)
In-Reply-To: <0f1f5bcd-815a-c070-5ba7-281f5a0ee146@twiddle.net>
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On 05/10/2017 03:19 PM, Richard Henderson wrote:
> On 05/10/2017 01:05 PM, Philippe Mathieu-Daudé wrote:
>> +-tcg_gen_shri_tl(ret, arg, ofs);
>> +-tcg_gen_andi_tl(ret, ret, len);
>> ++tcg_gen_extract_tl(ret, arg, ofs, len);
>
> You can't simply copy the and mask to the extract length.
>
> You need to verify it's all low bits and convert that to a count of the
> low bits. E.g. 0xff -> 8.
Coccinelle may still be able to do that, but it becomes a little less
obvious (and I'm not the expert to consult on what that would look like).
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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next prev parent reply other threads:[~2017-05-10 20:24 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-10 20:05 [Qemu-devel] [PATCH 0/8] optimize various tcg_gen() functions using extract op Philippe Mathieu-Daudé
2017-05-10 20:05 ` [Qemu-devel] [PATCH 1/8] coccinelle: add a script to optimize tcg op using tcg_gen_extract() Philippe Mathieu-Daudé
2017-05-10 20:12 ` Eric Blake
2017-05-10 20:23 ` Philippe Mathieu-Daudé
2017-05-10 20:19 ` Richard Henderson
2017-05-10 20:23 ` Eric Blake [this message]
2017-05-10 21:27 ` Philippe Mathieu-Daudé
2017-05-10 23:52 ` [Qemu-devel] [RFC PATCH v2] " Philippe Mathieu-Daudé
2017-05-11 0:13 ` Philippe Mathieu-Daudé
2017-05-11 9:03 ` Markus Armbruster
2017-05-12 2:01 ` Philippe Mathieu-Daudé
2017-05-12 2:04 ` Philippe Mathieu-Daudé
2017-05-15 7:04 ` Markus Armbruster
2017-05-10 20:05 ` [Qemu-devel] [PATCH 2/8] target/arm: optimize smul_dual() and neon_trn_u8() using extract op Philippe Mathieu-Daudé
2017-05-10 20:15 ` Eric Blake
2017-05-12 2:49 ` Philippe Mathieu-Daudé
2017-05-10 20:20 ` Richard Henderson
2017-05-10 20:32 ` Philippe Mathieu-Daudé
2017-05-12 1:31 ` Philippe Mathieu-Daudé
2017-05-10 20:05 ` [Qemu-devel] [PATCH 3/8] target/arm: optimize rev16() " Philippe Mathieu-Daudé
2017-05-12 1:54 ` Philippe Mathieu-Daudé
2017-05-10 20:05 ` [Qemu-devel] [PATCH 4/8] target/cris: optimize gen_swapb() " Philippe Mathieu-Daudé
2017-05-12 1:29 ` Philippe Mathieu-Daudé
2017-05-10 20:05 ` [Qemu-devel] [PATCH 5/8] target/m68k: optimize bcd_flags() " Philippe Mathieu-Daudé
2017-05-11 8:41 ` Laurent Vivier
2017-05-12 1:52 ` Philippe Mathieu-Daudé
2017-05-10 20:05 ` [Qemu-devel] [PATCH 6/8] target/mips: optimize bshfl() " Philippe Mathieu-Daudé
2017-05-12 2:13 ` Philippe Mathieu-Daudé
2017-05-10 20:05 ` [Qemu-devel] [PATCH 7/8] target/ppc: optimize various functions " Philippe Mathieu-Daudé
2017-05-11 0:41 ` David Gibson
2017-05-11 8:46 ` [Qemu-devel] [Qemu-ppc] " Laurent Vivier
2017-05-12 5:13 ` David Gibson
2017-05-11 4:54 ` [Qemu-devel] " Nikunj A Dadhania
2017-05-12 1:48 ` Philippe Mathieu-Daudé
2017-05-12 5:16 ` David Gibson
2017-05-10 20:05 ` [Qemu-devel] [PATCH 8/8] target/sparc: " Philippe Mathieu-Daudé
2017-05-12 1:50 ` Philippe Mathieu-Daudé
2017-05-10 20:20 ` [Qemu-devel] [PATCH 0/8] optimize various tcg_gen() " no-reply
2017-05-12 2:34 ` Philippe Mathieu-Daudé
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