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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/99927] [11 Regression] Wrong code since
 r11-39-gf9e1ea10e657af9f
Date: Wed, 07 Apr 2021 17:46:20 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99927

--- Comment #12 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Segher Boessenkool from comment #11)
> (In reply to Jakub Jelinek from comment #7)
> > Ah, create_log_links wants to work like that.
> > So, the bug seems to be that insn 108 has REG_DEAD (reg:CC 17 flags) no=
te.
> > It doesn't initially, but it is added during 106 -> 108 combination
>=20
> But that combination should never have been made: flags is set in insn 10=
7!

Why?  It is not across a LOG_LINK for the flags register, but for the r134
pseudo.  Yes, the first insn has a clobber on flags, but don't most of x86
insns have that?  The combiner doesn't move over the clobber, it just substs
r134 to its SET_SRC.=