[Bug target/113010] [RISCV] sign-extension lost in comparison with constant embedded in comma-op expression

["pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113010

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 familiar
> > with the combiner:
> 
> 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) == SIGN_EXTEND
      && HWI_COMPUTABLE_MODE_P (mode)
      && ((nonzero_bits (XEXP (x, 0), inner_mode)
           & ~(((unsigned HOST_WIDE_INT) GET_MODE_MASK (inner_mode)) >> 1))
          == 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 thought
it was the same.