[Bug middle-end/79238] Combine generates paradoxical subreg of memory

[vogt at linux dot vnet.ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79238

--- Comment #1 from Dominik Vogt <vogt at linux dot vnet.ibm.com> ---
Note: Reg 67 is


  (set (reg:SI 67 [ *f_5(D) ])
      (mem:SI (reg:DI 2 %r2 [ f ]) [1 *f_5(D)+0 S4 A32]))


Note 2: Combine tries

  (parallel [
        (set (reg/i:DI 2 %r2)
            (zero_extract:DI (mem:QI (plus:DI (reg:DI 2 %r2 [ f ])
                        (const_int 2 [0x2])) [1 *f_5(D)+2 S1 A16])
                (const_int 1 [0x1])
                (const_int 7 [0x7])))
        (clobber (reg:CC 33 %cc))
    ])

first and tries the (and) pattern from the first comment through
change_zero_ext when that does not match.