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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/113010] [RISCV] sign-extension lost in comparison with
 constant embedded in comma-op expression
Date: Tue, 09 Jan 2024 22:12:35 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113010

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2024-01-09
   Target Milestone|---                         |13.3

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #4)
> (In reply to Greg McGary from comment #3)
> > This fixes it, though I would like second look from someone more famili=
ar
> > with the combiner:
>=20
> I almost sure this is still an issue with WORD_REGISTER_OPERATIONS .

That is this is missing that check:

```
  /* Convert sign extension to zero extension, if we know that the high
     bit is not set, as this is easier to optimize.  It will be converted
     back to cheaper alternative in make_extraction.  */
  if (GET_CODE (x) =3D=3D SIGN_EXTEND
      && HWI_COMPUTABLE_MODE_P (mode)
      && ((nonzero_bits (XEXP (x, 0), inner_mode)
           & ~(((unsigned HOST_WIDE_INT) GET_MODE_MASK (inner_mode)) >> 1))
          =3D=3D 0))

```

Should most likely need the same check as what was added in r14-6806 . And =
yes
it a similar bug dealing with WORD_REGISTER_OPERATIONS  which is why I thou=
ght
it was the same.=