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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/104914] [MIPS] wrong comparison with scrabbled
 int value
Date: Fri, 07 Jul 2023 04:31:54 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104914

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=3D67736

--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to YunQiang Su from comment #8)
> (In reply to Andrew Pinski from comment #7)
> > The initial RTL has a signed extend in there:
> >=20
> >=20
> > (insn 20 19 23 2 (set (reg/v:DI 200 [ val+-4 ])
> >         (sign_extend:DI (subreg:SI (reg/v:DI 200 [ val+-4 ]) 4)))
> > "/app/example.cpp":7:29 -1
> >      (nil))
> > (jump_insn 23 20 24 2 (set (pc)
> >         (if_then_else (le (subreg/s/u:SI (reg/v:DI 200 [ val+-4 ]) 4)
> >                 (const_int 0 [0]))
> >             (label_ref 32)
> >             (pc))) "/app/example.cpp":8:5 -1
> >      (int_list:REG_BR_PROB 440234148 (nil))
> >  -> 32)
> >=20
> >=20
> > Before combine also looks fine:
> > (insn 20 19 23 2 (set (reg/v:DI 200 [ val+-4 ])
> >         (sign_extend:DI (subreg:SI (reg/v:DI 200 [ val+-4 ]) 4)))
> > "/app/example.cpp":7:29 235 {extendsidi2}
> >      (nil))
>=20
> Yes. I noticed it. while in mips.md,  extendsidi2 is expanded to no
> instructions at all.

Right then the le should had a truncation before the use of SI mode here ..=
.=