vdbpsadbw

Double Block Packed Sum-Absolute-Differences

VDBPSADBW zmm1 {k1}, zmm2, zmm3/m512, imm8

Computes SAD on 16-bit blocks.

Details

Computes double-block packed sum-of-absolute-differences on 16-bit blocks between src1 and src2, producing 16-bit results. The operation partitions each 128-bit lane into blocks of 16 bits, computes SAD across specified block boundaries controlled by imm8, and accumulates results into 16-bit fields. Requires AVX-512BW; operates on 512-bit vectors with EVEX masking.

Pseudocode Operation

for lane = 0 to 3 {
  for block = 0 to 3 {
    result = 0
    block_offset = (imm8 >> (block*2)) & 0x3
    for j = 0 to 1 {
      idx1 = lane*128 + block*32 + j*16
      idx2 = lane*128 + block_offset*32 + j*16
      result += abs(src1[idx1+15:idx1] - src2[idx2+15:idx2])
    }
    dest[lane*128 + block*16 + 15 : lane*128 + block*16] = result[15:0]
  }
}

Example

VDBPSADBW zmm1, zmm2, zmm3/m512, 3

Encoding

Binary Layout

EVEX

Format EVEX

Opcode EVEX.512.66.0F3A.W0 42 /r ib

Extension AVX-512BW

Operands

dest
512-bit ZMM AVX-512 register
src1
512-bit ZMM AVX-512 register
src2
512-bit ZMM AVX-512 register or Memory operand
src3
8-bit signed immediate

Reference (Intel® SDM)

Instruction Forms

Opcode	Instruction	Op/En	64/32-bit Mode	CPUID	Description
EVEX.128.66.0F3A.W0 42 /r ib	VDBPSADBW xmm1 {k1}{z}, xmm2, xmm3/m128, imm8	A	V/V	(AVX512VL AND AVX512BW) OR AVX10.1	Compute packed SAD word results of unsigned bytes in dword block from xmm2 with unsigned bytes of dword blocks transformed from xmm3/m128 using the shuffle controls in imm8. Results are written to xmm1 under the writemask k1.
EVEX.256.66.0F3A.W0 42 /r ib	VDBPSADBW ymm1 {k1}{z}, ymm2, ymm3/m256, imm8	A	V/V	(AVX512VL AND AVX512BW) OR AVX10.1	Compute packed SAD word results of unsigned bytes in dword block from ymm2 with unsigned bytes of dword blocks transformed from ymm3/m256 using the shuffle controls in imm8. Results are written to ymm1 under the writemask k1.
EVEX.512.66.0F3A.W0 42 /r ib	VDBPSADBW zmm1 {k1}{z}, zmm2, zmm3/m512, imm8	A	V/V	AVX512BW OR AVX10.1	Compute packed SAD word results of unsigned bytes in dword block from zmm2 with unsigned bytes of dword blocks transformed from zmm3/m512 using the shuffle controls in imm8. Results are written to zmm1 under the writemask k1.

Instruction Operand Encoding

Op/En	Tuple Type	Operand 1	Operand 2	Operand 3	Operand 4
A	Full Mem	ModRM:reg (w)	EVEX.vvvv (r)	ModRM:r/m (r)	imm8

Description

Compute packed SAD (sum of absolute differences) word results of unsigned bytes from two 32-bit dword elements. Packed SAD word results are calculated in multiples of qword superblocks, producing 4 SAD word results in each 64-bit superblock of the destination register. Within each super block of packed word results, the SAD results from two 32-bit dword elements are calculated as follows: • The lower two word results are calculated each from the SAD operation between a sliding dword element within a qword superblock from an intermediate vector with a stationary dword element in the corresponding qword superblock of the first source operand. The intermediate vector, see “Tmp1” in Figure 5-8, is constructed from the second source operand the imm8 byte as shuffle control to select dword elements within a 128-bit lane of the second source operand. The two sliding dword elements in a qword superblock of Tmp1 are located at byte offset 0 and 1 within the superblock, respectively. The stationary dword element in the qword superblock from the first source operand is located at byte offset 0. • The next two word results are calculated each from the SAD operation between a sliding dword element within a qword superblock from the intermediate vector Tmp1 with a second stationary dword element in the corresponding qword superblock of the first source operand. The two sliding dword elements in a qword superblock of Tmp1 are located at byte offset 2and 3 within the superblock, respectively. The stationary dword element in the qword superblock from the first source operand is located at byte offset 4. • The intermediate vector is constructed in 128-bits lanes. Within each 128-bit lane, each dword element of the intermediate vector is selected by a two-bit field within the imm8 byte on the corresponding 128-bits of the second source operand. The imm8 byte serves as dword shuffle control within each 128-bit lanes of the intermediate vector and the second source operand, similarly to PSHUFD. The first source operand is a ZMM/YMM/XMM register. The second source operand is a ZMM/YMM/XMM register, or a 512/256/128-bit memory location. The destination operand is conditionally updated based on writemask k1 at 16-bit word granularity. VDBPSADBW—Double Block Packed Sum-Absolute-Differences (SAD) on Unsigned Bytes Vol. 2C 5-154 127+128*n 95+128*n 63+128*n 31+128*n 128*n 128-bit Lane of Src2 DW3 DW2 DW1 DW0 00B: DW0 01B: DW1 imm8 shuffle control 10B: DW2 11B: DW3 7 5 3 1 0 127+128*n 95+128*n 63+128*n 31+128*n 128*n 128-bit Lane of Tmp1 Tmp1 qword superblock 55 47 39 31 24 39 31 23 15 8 Tmp1 sliding dword Tmp1 sliding dword 63 55 47 39 32 31 23 15 7 0 Src1 stationary dword 0 Src1 stationary dword 1 _ _ _ _ _ _ _ _ abs abs abs abs abs abs abs abs + 47 39 31 23 16 + 31 23 15 7 0 Tmp1 sliding dword Tmp1 sliding dword 63 55 47 39 32 31 23 15 7 0 Src1 stationary dword 1 _ _ _ _ Src1 stationary dword 0 _ _ _ _ abs abs abs abs abs abs abs abs + + 63 47 31 15 0 Destination qword superblock Figure 5-8. 64-bit Super Block of SAD Operation in VDBPSADBW

Operation

VDBPSADBW (EVEX Encoded Versions)
(KL, VL) = (8, 128), (16, 256), (32, 512)
Selection of quadruplets:
FOR I = 0 to VL step 128
TMP1[I+31:I] := select (SRC2[I+127: I], imm8[1:0])
TMP1[I+63: I+32] := select (SRC2[I+127: I], imm8[3:2])
TMP1[I+95: I+64] := select (SRC2[I+127: I], imm8[5:4])
TMP1[I+127: I+96] := select (SRC2[I+127: I], imm8[7:6])
END FOR

SAD of quadruplets:

FOR I =0 to VL step 64
TMP_DEST[I+15:I] := ABS(SRC1[I+7: I] - TMP1[I+7: I]) +
ABS(SRC1[I+15: I+8]- TMP1[I+15: I+8]) +



VDBPSADBW—Double Block Packed Sum-Absolute-Differences (SAD) on Unsigned Bytes                                                     Vol. 2C 5-155
ABS(SRC1[I+23: I+16]- TMP1[I+23: I+16]) +
ABS(SRC1[I+31: I+24]- TMP1[I+31: I+24])

TMP_DEST[I+31: I+16] := ABS(SRC1[I+7: I] - TMP1[I+15: I+8]) +
ABS(SRC1[I+15: I+8]- TMP1[I+23: I+16]) +
ABS(SRC1[I+23: I+16]- TMP1[I+31: I+24]) +
ABS(SRC1[I+31: I+24]- TMP1[I+39: I+32])
TMP_DEST[I+47: I+32] := ABS(SRC1[I+39: I+32] - TMP1[I+23: I+16]) +
ABS(SRC1[I+47: I+40]- TMP1[I+31: I+24]) +
ABS(SRC1[I+55: I+48]- TMP1[I+39: I+32]) +
ABS(SRC1[I+63: I+56]- TMP1[I+47: I+40])

TMP_DEST[I+63: I+48] := ABS(SRC1[I+39: I+32] - TMP1[I+31: I+24]) +
ABS(SRC1[I+47: I+40] - TMP1[I+39: I+32]) +
ABS(SRC1[I+55: I+48] - TMP1[I+47: I+40]) +
ABS(SRC1[I+63: I+56] - TMP1[I+55: I+48])
ENDFOR

FOR j := 0 TO KL-1
i :=     j * 16
IF k1[j] OR *no writemask*
THEN DEST[i+15:i] := TMP_DEST[i+15:i]
ELSE
IF *merging-masking*                                 ; merging-masking
THEN *DEST[i+15:i] remains unchanged*
ELSE                                                         ; zeroing-masking
DEST[i+15:i] := 0
FI
FI;
ENDFOR
DEST[MAXVL-1:VL] := 0

Intel C/C++ Compiler Intrinsic Equivalent

VDBPSADBW __m512i _mm512_dbsad_epu8(__m512i a, __m512i b int imm8);
VDBPSADBW __m512i _mm512_mask_dbsad_epu8(__m512i s, __mmask32 m, __m512i a, __m512i b int imm8);
VDBPSADBW __m512i _mm512_maskz_dbsad_epu8(__mmask32 m, __m512i a, __m512i b int imm8);
VDBPSADBW __m256i _mm256_dbsad_epu8(__m256i a, __m256i b int imm8);
VDBPSADBW __m256i _mm256_mask_dbsad_epu8(__m256i s, __mmask16 m, __m256i a, __m256i b int imm8);
VDBPSADBW __m256i _mm256_maskz_dbsad_epu8(__mmask16 m, __m256i a, __m256i b int imm8);
VDBPSADBW __m128i _mm_dbsad_epu8(__m128i a, __m128i b int imm8);
VDBPSADBW __m128i _mm_mask_dbsad_epu8(__m128i s, __mmask8 m, __m128i a, __m128i b int imm8);
VDBPSADBW __m128i _mm_maskz_dbsad_epu8(__mmask8 m, __m128i a, __m128i b int imm8);

Exceptions

SIMD Floating-Point Exceptions

None.

Other Exceptions

See Exceptions Type E4NF.nb in Table 2-52, “Type E4NF Class Exception Conditions.” VDBPSADBW—Double Block Packed Sum-Absolute-Differences (SAD) on Unsigned Bytes Vol. 2C 5-156