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))
