[Bug rtl-optimization/83827] vector load/store with struct in registers

["crazylht at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83827

--- Comment #4 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Hongtao.liu from comment #2)
> For f, pass_combine failed 
> 
> Trying 20, 21 -> 22:
>    20: clobber r83:TI
>    21: r83:TI#0=r88:DI
>       REG_DEAD r88:DI
>    22: r83:TI#8=r89:DI
>       REG_DEAD r89:DI
> Can't combine i2 into i3
> 
> (insn 20 6 21 2 (clobber (reg/v:TI 83 [ x ])) "test.cpp":3:11 -1
>      (nil))
Clobber was generate by simplify_gen_subreg_concatn to simplify  

(insn 4 3 5 2 (set (concatn:TI [
                (reg:DI 88)
                (reg:DI 89 [+8 ])
            ])
        (const_int 0 [0]))
"/export/users2/liuhongt/tools-build/build_intel-innersource_master_debug/test.cpp":3:11
73 {*movti_internal}
     (nil))

(insn 5 4 6 2 (set (subreg:DF (reg:TI 84) 0)
        (reg:DF 85)) "test.cpp":3:11 133 {*movdf_internal}
     (nil))
(insn 6 5 7 2 (set (subreg:DF (reg:TI 84) 8)
        (reg:DF 86)) "test.cpp":3:11 133 {*movdf_internal}
     (nil))

to

(insn 17 3 18 2 (set (reg:DI 88)
        (reg:DI 85)) "test1.cpp":3:11 74 {*movdi_internal}
     (nil))
(insn 18 17 5 2 (set (reg:DI 89 [+8 ])
        (const_int 0 [0])) "test1.cpp":3:11 74 {*movdi_internal}
     (nil))
(insn 5 18 19 2 (set (reg:DI 89 [+8 ])
        (reg:DI 86)) "test1.cpp":3:11 74 {*movdi_internal}
     (nil))
(insn 19 5 20 2 (clobber (reg/v:TI 83 [ x ])) "test1.cpp":3:11 -1
     (nil))
(insn 20 19 21 2 (set (subreg:DI (reg/v:TI 83 [ x ]) 0)
        (reg:DI 88)) "test1.cpp":3:11 74 {*movdi_internal}
     (nil))
(insn 21 20 7 2 (set (subreg:DI (reg/v:TI 83 [ x ]) 8)
        (reg:DI 89 [+8 ])) "test1.cpp":3:11 74 {*movdi_internal}
     (nil))