KUNPCKBW/KUNPCKWD/KUNPCKDQ - Unpack for Mask Registers

Opcode/ Instruction

Op/En

64/32 bit Mode Support

CPUID Feature Flag

Description

VEX.L1.66.0F.W0 4B /r KUNPCKBW k1, k2, k3

RVR

V/V

AVX512F

Unpack 8-bit masks in k2 and k3 and write word result in k1.

VEX.L1.0F.W0 4B /r KUNPCKWD k1, k2, k3

RVR

V/V

AVX512BW

Unpack 16-bit masks in k2 and k3 and write doubleword result in k1.

VEX.L1.0F.W1 4B /r KUNPCKDQ k1, k2, k3

RVR

V/V

AVX512BW

Unpack 32-bit masks in k2 and k3 and write quadword result in k1.

Instruction Operand Encoding

Op/En

Operand 1

Operand 2

Operand 3

RVR

ModRM:reg (w)

VEX.1vvv (r)

ModRM:r/m (r, ModRM:[7:6] must be 11b)

Description

Unpacks the lower 8/16/32 bits of the second and third operands (source operands) into the low part of the first operand (destination operand), starting from the low bytes. The result is zero-extended in the destination.

Operation

KUNPCKBW 

DEST[7:0] := SRC2[7:0]
DEST[15:8] := SRC1[7:0]
DEST[MAX_KL-1:16] := 0

KUNPCKWD 

DEST[15:0] := SRC2[15:0]
DEST[31:16] := SRC1[15:0]
DEST[MAX_KL-1:32] := 0

KUNPCKDQ 

DEST[31:0] := SRC2[31:0]
DEST[63:32] := SRC1[31:0]
DEST[MAX_KL-1:64] := 0

Intel C/C++ Compiler Intrinsic Equivalent 

KUNPCKBW __mmask16 _mm512_kunpackb(__mmask16 a, __mmask16 b);
KUNPCKDQ __mmask64 _mm512_kunpackd(__mmask64 a, __mmask64 b);
KUNPCKWD __mmask32 _mm512_kunpackw(__mmask32 a, __mmask32 b);

Flags Affected

None.

SIMD Floating-Point Exceptions

None.

Other Exceptions

See Table 2-63, "TYPE K20 Exception Definition (VEX-Encoded OpMask Instructions w/o Memory Arg)."