https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103124
--- Comment #3 from HaoChen Gui <guihaoc at gcc dot gnu.org> ---
My solution is to split the move (from TI to V1TI) into one vsx_concat_v2di and
one V2DI to V1TI move. Thus, TI register 122 can be decomposed.
(insn 12 11 17 2 (set (reg:V1TI 121 [ b ])
(subreg:V1TI (reg:TI 122 [ a ]) 0)) "test2.c":4:5 1167
{vsx_movv1ti_64bit}
(expr_list:REG_DEAD (reg:TI 122 [ a ])
(nil)))
//after split pass
(insn 23 11 24 2 (set (reg:V2DI 125)
(vec_concat:V2DI (subreg:DI (reg:TI 122 [ a ]) 0)
(subreg:DI (reg:TI 122 [ a ]) 8))) "test2.c":4:5 -1
(nil))
(insn 24 23 17 2 (set (reg:V1TI 121 [ b ])
(subreg:V1TI (reg:V2DI 125) 0)) "test2.c":4:5 -1
(nil))
//after subreg pass
(insn 23 11 24 2 (set (reg:V2DI 125)
(vec_concat:V2DI (reg:DI 126 [ a ])
(reg:DI 127 [ a+8 ]))) "test2.c":4:5 1346 {vsx_concat_v2di}
(nil))
(insn 24 23 17 2 (set (reg:V1TI 121 [ b ])
(subreg:V1TI (reg:V2DI 125) 0)) "test2.c":4:5 1167 {vsx_movv1ti_64bit}
(nil))
