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Re: [Qemu-devel] [PATCH 1/8] coccinelle: add a script to optimize tcg op


From: Richard Henderson
Subject: Re: [Qemu-devel] [PATCH 1/8] coccinelle: add a script to optimize tcg op using tcg_gen_extract()
Date: Wed, 10 May 2017 13:19:58 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0

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.


r~



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