[Bug target/63678] __mm256_blend_epi16 only accepts 8-bit masks (should accept 16-bit)

[peter.bumbulis at ianywhere dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63678

--- Comment #2 from Peter Bumbulis <peter.bumbulis at ianywhere dot com> ---
The referenced web page is incorrect.  Look in the instruction set reference
manual
(https://software.intel.com/sites/default/files/managed/c6/a9/319433-020.pdf,
search for VPBLENDMW) or the intrinsics guide
(https://software.intel.com/sites/landingpage/IntrinsicsGuide/).

These instructions blend 16 bit quantities:  you can fit 16 of these in a 256
bit register.  For AVX512 it's a 32-bit constant.