[Bug tree-optimization/102494] Failure to optimize vector reduction properly especially when using OpenMP

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102494

--- Comment #7 from Hongtao.liu <crazylht at gmail dot com> ---
After supporting v4hi reduce, gimple seems not optimal to convert v8qi to v8hi.

 6  vector(4) short int vect__21.36;
 7  vector(4) unsigned short vect__2.31;
 8  int16_t stmp_r_17.17;
 9  vector(8) short int vect__16.15;
10  int16_t D.2229[8];
11  vector(8) short int _50;
12  vector(8) short int _51;
13  vector(8) short int _52;
14  vector(8) short int _53;
15  vector(8) short int _54;
16  vector(8) short int _55;

18  <bb 2> [local count: 189214783]:
19  vect__2.31_97 = [vec_unpack_lo_expr] a_90(D);
20  vect__2.31_98 = [vec_unpack_hi_expr] a_90(D);
21  vect__21.36_105 = VIEW_CONVERT_EXPR<vector(4) short int>(vect__2.31_97);
22  vect__21.36_106 = VIEW_CONVERT_EXPR<vector(4) short int>(vect__2.31_98);
23  MEM <vector(4) short int> [(short int *)&D.2229] = vect__21.36_105;
24  MEM <vector(4) short int> [(short int *)&D.2229 + 8B] = vect__21.36_106;
25  vect__16.15_47 = MEM <vector(8) short int> [(short int *)&D.2229];