[Bug rtl-optimization/101076] RTL Combine pass won't generate sign_extnd RTX in some senario

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101076

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
     Ever confirmed|0                           |1
   Last reconfirmed|2021-06-15 00:00:00         |2023-06-02
             Status|UNCONFIRMED                 |NEW

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I remember running into this issue with MIPS too.

There we got:

(set (reg:SI 197 [ aD.2145 ])
    (ashiftrt:SI (truncate:SI (ashift:DI (reg:DI 199)
                (const_int 16 [0x10])))
        (const_int 16 [0x10])))

Or even worse:

(set (reg/i:DI 2 $2)
    (sign_extend:DI (ashiftrt:SI (truncate:SI (ashift:DI (reg:DI 199)
                    (const_int 16 [0x10])))
            (const_int 16 [0x10]))))