the opmask registers have a new mini extension of instructions operating directly on them. unlike the rest of the avx-512 instructions, these instructions are all vex encoded. the initial opmask instructions are all 16-bit (word) versions. with avx-512dq 8-bit (byte) versions were added to better match the needs of masking 8 64-bit values, and with avx-512bw 32-bit (double) and 64-bit (quad) versions were added so they can mask up to 64 8-bit values. the instructions kortest and ktest can be used to set the x86 flags based on mask registers, so that they may be used together with non-simd x86 branch and conditional instructions.