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Re: [Qemu-devel] [PATCH 1/8] coccinelle: add a script to optimize tcg op
From: |
Eric Blake |
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 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 |
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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- [Qemu-devel] [PATCH 0/8] optimize various tcg_gen() functions using extract op, Philippe Mathieu-Daudé, 2017/05/10
- [Qemu-devel] [PATCH 1/8] coccinelle: add a script to optimize tcg op using tcg_gen_extract(), Philippe Mathieu-Daudé, 2017/05/10
- Re: [Qemu-devel] [PATCH 1/8] coccinelle: add a script to optimize tcg op using tcg_gen_extract(), Eric Blake, 2017/05/10
- Re: [Qemu-devel] [PATCH 1/8] coccinelle: add a script to optimize tcg op using tcg_gen_extract(), Richard Henderson, 2017/05/10
- Re: [Qemu-devel] [PATCH 1/8] coccinelle: add a script to optimize tcg op using tcg_gen_extract(),
Eric Blake <=
- Re: [Qemu-devel] [PATCH 1/8] coccinelle: add a script to optimize tcg op using tcg_gen_extract(), Philippe Mathieu-Daudé, 2017/05/10
- [Qemu-devel] [RFC PATCH v2] coccinelle: add a script to optimize tcg op using tcg_gen_extract(), Philippe Mathieu-Daudé, 2017/05/10
- Re: [Qemu-devel] [RFC PATCH v2] coccinelle: add a script to optimize tcg op using tcg_gen_extract(), Philippe Mathieu-Daudé, 2017/05/10
- Re: [Qemu-devel] [RFC PATCH v2] coccinelle: add a script to optimize tcg op using tcg_gen_extract(), Markus Armbruster, 2017/05/11
- Re: [Qemu-devel] [RFC PATCH v2] coccinelle: add a script to optimize tcg op using tcg_gen_extract(), Philippe Mathieu-Daudé, 2017/05/11
- Re: [Qemu-devel] [RFC PATCH v2] coccinelle: add a script to optimize tcg op using tcg_gen_extract(), Philippe Mathieu-Daudé, 2017/05/11
- Re: [Qemu-devel] [RFC PATCH v2] coccinelle: add a script to optimize tcg op using tcg_gen_extract(), Markus Armbruster, 2017/05/15
[Qemu-devel] [PATCH 2/8] target/arm: optimize smul_dual() and neon_trn_u8() using extract op, Philippe Mathieu-Daudé, 2017/05/10