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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/109907] Missed optimization for bit extraction (uses shift instead of single bit-test)
Date: Sun, 21 May 2023 05:36:35 +0000 [thread overview]
Message-ID: <bug-109907-4-Q42hB7T4rz@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-109907-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109907
--- Comment #16 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #14)
> Actually I take back on what is going on those 3. But I will be looking into
> it.
>
>
> x.0_1 = (signed long) x_4(D);
> _2 = x.0_1 >> 31;
> _3 = (unsigned char) _2;
> _5 = _3 & 1;
we could pattern match this on the gimple using something like:
(simplify
(bit_and (convert? (rshift (nop_convert? @1) INTEGER_CST@2)) integer_onep)
(if (wi::to_wide (@2) == TYPE_PRECISION (TREE_TYPE (@0)) - 1)
(with
{ tree utype = unsigned_type_for (type); }
(convert (rshift (convert:utype @1) @2)))
But that still fails because combine really does not like subregs:
Trying 6 -> 12:
6: r47:SI=r48:SI 0>>0x1f
REG_DEAD r48:SI
12: r24:QI=r47:SI#0
REG_DEAD r47:SI
Failed to match this instruction:
(set (reg/i:QI 24 r24)
(subreg:QI (lshiftrt:SI (reg:SI 48)
(const_int 31 [0x1f])) 0))
next prev parent reply other threads:[~2023-05-21 5:36 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-19 10:10 [Bug middle-end/109907] New: [avr] " gjl at gcc dot gnu.org
2023-05-19 14:14 ` [Bug middle-end/109907] " pinskia at gcc dot gnu.org
2023-05-19 15:42 ` [Bug middle-end/109907] " pinskia at gcc dot gnu.org
2023-05-19 15:45 ` pinskia at gcc dot gnu.org
2023-05-19 20:03 ` pinskia at gcc dot gnu.org
2023-05-19 20:12 ` pinskia at gcc dot gnu.org
2023-05-19 20:41 ` gjl at gcc dot gnu.org
2023-05-19 20:55 ` pinskia at gcc dot gnu.org
2023-05-19 20:59 ` gjl at gcc dot gnu.org
2023-05-20 0:46 ` pinskia at gcc dot gnu.org
2023-05-20 5:09 ` pinskia at gcc dot gnu.org
2023-05-20 7:36 ` gjl at gcc dot gnu.org
2023-05-20 7:50 ` gjl at gcc dot gnu.org
2023-05-20 22:23 ` pinskia at gcc dot gnu.org
2023-05-20 22:40 ` pinskia at gcc dot gnu.org
2023-05-21 5:15 ` pinskia at gcc dot gnu.org
2023-05-21 5:36 ` pinskia at gcc dot gnu.org [this message]
2023-05-21 9:09 ` gjl at gcc dot gnu.org
2023-05-21 9:55 ` gjl at gcc dot gnu.org
2023-05-23 9:58 ` gjl at gcc dot gnu.org
2023-05-26 8:49 ` gjl at gcc dot gnu.org
2023-05-26 11:14 ` gjl at gcc dot gnu.org
2023-05-26 15:21 ` pinskia at gcc dot gnu.org
2023-05-26 16:08 ` gjl at gcc dot gnu.org
2023-05-26 23:11 ` pinskia at gcc dot gnu.org
2023-05-26 23:34 ` pinskia at gcc dot gnu.org
2023-05-26 23:49 ` pinskia at gcc dot gnu.org
2023-05-27 0:36 ` pinskia at gcc dot gnu.org
2023-05-27 4:02 ` pinskia at gcc dot gnu.org
2023-05-27 20:09 ` pinskia at gcc dot gnu.org
2023-06-11 9:22 ` cvs-commit at gcc dot gnu.org
2023-06-11 9:26 ` gjl at gcc dot gnu.org
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