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From: "rsandifo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/107991] [10/11/12/13 Regression] Extra mov
 instructions with ternary on x86
Date: Wed, 21 Dec 2022 13:15:15 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107991

--- Comment #5 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.or=
g> ---
>From a slightly old build, but it looks like we have a redundant move:

(insn 4 27 28 2 (set (reg/v:SI 85 [ i ])
        (reg:SI 91)) "foo.c":9:31 83 {*movsi_internal}
     (expr_list:REG_DEAD (reg:SI 91)
        (nil)))

This causes problems because we can then assign different preferences
and costs to 85 and 91.  91 comes from input register SI and so prefers
SIREG while 85 feeds the result and so prefers AREG.

We should be able to cope better with this, will have a look in the new
year.

The output seems better with -fweb.=