[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 #4 from Peter Bumbulis <peter.bumbulis at ianywhere dot com> ---
(In reply to Peter Bumbulis from comment #2)
> 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.

My mistake:  it looks like the generated code only uses the low 8 bytes.  Sorry
for any wasted bandwidth.