From: Eric Botcazou <botcazou@adacore.com>
To: Claudiu Zissulescu Ianculescu <claziss@gmail.com>
Cc: gcc@gcc.gnu.org
Subject: Re: Possible regression in DF analysis
Date: Thu, 08 Dec 2022 12:33:12 +0100 [thread overview]
Message-ID: <2858689.e9J7NaK4W3@fomalhaut> (raw)
In-Reply-To: <CAL0iMy2hQUyt8vyXSvdt9RvB3WTKFc6zWJqtQDiKNuJ+ZtwEPQ@mail.gmail.com>
> However, after this optimization I get the CC reg being dead after
> JUMP_INSN 15, which may lead to wrong code gen. Here it is the dump
> from fwprop1:
>
> (insn 14 11 15 3 (set (reg:CC 66 cc)
> (compare:CC (reg/v:SI 98 [ bytes ])
> (const_int 8 [0x8]))) "bad_cc.c":11:8 406 {cmpsi}
> (nil))
> (jump_insn 15 14 16 3 (set (pc)
> (if_then_else (gtu (reg:CC 66 cc)
> (const_int 0 [0]))
> (label_ref 27)
> (pc))) "bad_cc.c":11:8 15 {condjump}
> (expr_list:REG_DEAD (reg:CC 66 cc)
> (int_list:REG_BR_PROB 955630228 (nil)))
> -> 27)
> (note 16 15 18 4 [bb 4] NOTE_INSN_BASIC_BLOCK)
> (jump_insn 18 16 19 4 (set (pc)
> (if_then_else (eq (reg:CC 66 cc)
> (const_int 0 [0]))
> (label_ref:DI 34)
> (pc))) "bad_cc.c":12:10 15 {condjump}
> (expr_list:REG_DEAD (reg:CC 66 cc)
> (int_list:REG_BR_PROB 365072228 (nil)))
> -> 34)
>
> Please observe the REG_DEAD note on the both jump instructions.
Passes that consume REG_DEAD/REG_UNUSED notes need to recompute them
explicitly, they are not updated on the fly.
--
Eric Botcazou
next prev parent reply other threads:[~2022-12-08 11:33 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-08 10:40 Claudiu Zissulescu Ianculescu
2022-12-08 11:33 ` Eric Botcazou [this message]
2022-12-08 11:51 ` Claudiu Zissulescu Ianculescu
2022-12-13 8:41 ` Eric Botcazou
2022-12-13 12:30 ` Claudiu Zissulescu Ianculescu
2022-12-13 16:53 ` Claudiu Zissulescu Ianculescu
2022-12-13 17:01 ` Richard Biener
2022-12-13 17:38 ` Claudiu Zissulescu Ianculescu
2022-12-14 10:37 ` Claudiu Zissulescu Ianculescu
2022-12-14 11:06 ` Richard Biener
2022-12-14 11:30 ` Claudiu Zissulescu Ianculescu
2022-12-14 12:39 ` Richard Biener
2022-12-17 0:33 ` Jeff Law
[not found] ` <CAL0iMy1ad0PmprQdu6BMhHdivPz--1Yq72+n02Lj-SmxhZmxQQ@mail.gmail.com>
2022-12-20 12:34 ` Fwd: " Claudiu Zissulescu Ianculescu
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