[Bug target/101579] Suboptimal codegen for __builtin_shufflevector

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101579

--- Comment #5 from Hongtao.liu <crazylht at gmail dot com> ---
After manually eliminating the upper part vector shuffle, codegen is much
better https://godbolt.org/z/d3YhzzYfo

typedef unsigned int __attribute__((__vector_size__ (32))) U;
typedef unsigned char __attribute__((__vector_size__ (32))) V;

V g;

U
foo (void)
{
  V v = __builtin_shufflevector (g, g,
                                 0, 1, 2, 0, 5, 1, 0, 1, 3, 2, 3, 0, 4, 3, 1,
2,
                                 2, 0, 4, 2, 3, 1, 1, 2, 3, 4, 1, 1, 0, 0, 5,
2)
;
  v ^= 255;
  V w = v + g;
  U u = ((union { V a; U b; }) w).b + ((union { V a; U b; }) w).b[1];
  return u;
}