The toolchain's assembler corpus carries 195 amd64 encodings the
x/arch decoder rejects or degenerates: the BMI1/BMI2 VEX families
(ANDN, BEXTR, BLSI, BLSMSK, BLSR, BZHI, MULX, PDEP, PEXT, RORX,
SARX, SHLX, SHRX), the 0F 01 quartet CLAC, STAC, RDPKRU and WRPKRU,
the bare and REX-only RDSEED forms, and UD1. The supplementary
naming table decodes the VEX prefix and the ModR/M shape and renders
the toolchain's own spellings; every corpus row is pinned in the
unlisted fixture and round-trips byte for byte through the encoder,
and the boundary test pins the prefix shapes no family carries.
Assisted-by: GLM 5.3