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From: "segher at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/78103] Failure to optimize with __builtin_clzl
Date: Mon, 26 Jul 2021 21:01:01 +0000 [thread overview]
Message-ID: <bug-78103-4-G4RIqQ8S8k@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-78103-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78103
--- Comment #13 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #10)
> Unfortunately, it doesn't work for the #c0 testcase, after the combiner
> splitter kicks in, the combiner doesn't even try that 4 insn combination.
It does for me?
Trying 10, 13, 12 -> 14:
10: {r86:DI=r86:DI^0x3f;clobber flags:CC;}
REG_UNUSED flags:CC
13: r88:DI=0x40
12: r87:DI=sign_extend(r86:DI#0)
REG_DEAD r86:DI
14: {r85:DI=r88:DI-r87:DI;clobber flags:CC;}
REG_DEAD r88:DI
REG_DEAD r87:DI
REG_UNUSED flags:CC
REG_EQUAL 0x40-r87:DI
Failed to match this instruction:
(parallel [
(set (reg/v:DI 85 [ x ])
(minus:DI (const_int 64 [0x40])
(xor:DI (sign_extend:DI (subreg:SI (reg:DI 86) 0))
(const_int 63 [0x3f]))))
(clobber (reg:CC 17 flags))
])
Failed to match this instruction:
(set (reg/v:DI 85 [ x ])
(minus:DI (const_int 64 [0x40])
(xor:DI (sign_extend:DI (subreg:SI (reg:DI 86) 0))
(const_int 63 [0x3f]))))
Successfully matched this instruction:
(set (reg:DI 88)
(sign_extend:DI (subreg:SI (reg:DI 86) 0)))
Failed to match this instruction:
(set (reg/v:DI 85 [ x ])
(minus:DI (const_int 64 [0x40])
(xor:DI (reg:DI 88)
(const_int 63 [0x3f]))))
(Because 13 is a move from constant, 4-insn is allowed here).
next prev parent reply other threads:[~2021-07-26 21:01 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-78103-4@http.gcc.gnu.org/bugzilla/>
2021-07-24 6:20 ` pinskia at gcc dot gnu.org
2021-07-24 12:28 ` jakub at gcc dot gnu.org
2021-07-26 10:57 ` jakub at gcc dot gnu.org
2021-07-26 11:14 ` jakub at gcc dot gnu.org
2021-07-26 11:22 ` jakub at gcc dot gnu.org
2021-07-26 12:11 ` jakub at gcc dot gnu.org
2021-07-26 21:01 ` segher at gcc dot gnu.org [this message]
2021-07-26 21:08 ` jakub at gcc dot gnu.org
2021-07-26 21:26 ` segher at gcc dot gnu.org
2021-07-27 8:52 ` jakub at gcc dot gnu.org
2021-07-27 12:35 ` segher at gcc dot gnu.org
2021-07-27 12:41 ` jakub at gcc dot gnu.org
2021-07-27 13:53 ` jakub at gcc dot gnu.org
2021-07-27 15:25 ` segher at gcc dot gnu.org
2021-07-27 15:37 ` segher at gcc dot gnu.org
2021-07-31 7:21 ` cvs-commit at gcc dot gnu.org
2021-07-31 8:24 ` jakub at gcc dot gnu.org
2021-08-01 20:33 ` cvs-commit at gcc dot gnu.org
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