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

[Richard Henderson]

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~