Use pblendw instead of pand to clear upper 16 bits.
For vec_pack_truncv8si/v4si w/o AVX512,
(const_vector:v4si (const_int 0xffff) x4) is used as mask to clear
upper 16 bits, but vpblendw with zero_vector can also be used, and
zero vector is cheaper than (const_vector:v4si (const_int 0xffff) x4).
gcc/ChangeLog:
PR target/114427
* config/i386/i386-expand.cc (expand_vec_perm_even_odd_pack):
Use pblendw instead of pand to clear upper bits.
gcc/testsuite/ChangeLog:
* gcc.target/i386/pr114427.c: New test.