PSADBW—Compute Sum of Absolute Differences

Opcode/Instruction Op/En 64/32 bit Mode Support CPUID Feature Flag Description

0F F6 /r1

PSADBW mm1, mm2/m64

 RM V/V SSE Computes the absolute differences of the packed unsigned byte integers from mm2 /m64 and mm1; differences are then summed to produce an unsigned word integer result.

66 0F F6 /r

PSADBW xmm1, xmm2/m128

 RM V/V SSE2 Computes the absolute differences of the packed unsigned byte integers from xmm2 /m128 and xmm1; the 8 low differences and 8 high differences are then summed separately to produce two unsigned word integer results.

VEX.NDS.128.66.0F.WIG F6 /r

VPSADBW xmm1, xmm2, xmm3/m128

 RVM V/V AVX Computes the absolute differences of the packed unsigned byte integers from xmm3 /m128 and xmm2; the 8 low differences and 8 high differences are then summed separately to produce two unsigned word integer results.

VEX.NDS.256.66.0F.WIG F6 /r

VPSADBW ymm1, ymm2, ymm3/m256

 RVM V/V AVX2 Computes the absolute differences of the packed unsigned byte integers from ymm3 /m256 and ymm2; then each consecutive 8 differences are summed separately to produce four unsigned word integer results.

NOTES:

1. See note in Section 2.4, “Instruction Exception Specification” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2A and Section 22.25.3, “Exception Conditions of Legacy SIMD Instructions Operating on MMX Registers” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3A.

Instruction Operand Encoding

Op/En Operand 1 Operand 2 Operand 3 Operand 4
RM ModRM:reg (r, w) ModRM:r/m (r) NA NA
RVM ModRM:reg (w) VEX.vvvv (r) ModRM:r/m (r) NA

Description

Computes the absolute value of the difference of 8 unsigned byte integers from the source operand (second operand) and from the destination operand (first operand). These 8 differences are then summed to produce an unsigned word integer result that is stored in the destination operand. Figure 4-10 shows the operation of the PSADBW instruction when using 64-bit operands.

When operating on 64-bit operands, the word integer result is stored in the low word of the destination operand, and the remaining bytes in the destination operand are cleared to all 0s.

When operating on 128-bit operands, two packed results are computed. Here, the 8 low-order bytes of the source and destination operands are operated on to produce a word result that is stored in the low word of the destination operand, and the 8 high-order bytes are operated on to produce a word result that is stored in bits 64 through 79 of the destination operand. The remaining bytes of the destination operand are cleared.

In 64-bit mode, using a REX prefix in the form of REX.R permits this instruction to access additional registers (XMM8-XMM15).

Legacy SSE version: The source operand can be an MMX technology register or a 64-bit memory location. The destination operand is an MMX technology register.

128-bit Legacy SSE version: The first source operand and destination register are XMM registers. The second source operand is an XMM register or a 128-bit memory location. Bits (VLMAX-1:128) of the corresponding YMM destination register remain unchanged.

VEX.128 encoded version: The first source operand and destination register are XMM registers. The second source operand is an XMM register or a 128-bit memory location. Bits (VLMAX-1:128) of the destination YMM register are zeroed.

VEX.256 encoded version: The first source operand and destination register are YMM registers. The second source operand is an YMM register or a 256-bit memory location.

Note: VEX.L must be 0, otherwise the instruction will #UD.

SRC X2 DEST TEMP DEST Y3 Y1 Y0 Y2 X7 X6 Y5 ABS(X7:Y7) X5 X3 X1 Y7 Y4 ABS(X4:Y4) ABS(X1:Y1) ABS(X0:Y0) 00H 00H 00H 00H 00H X4 X0 Y6 00H SUM(TEMP7...TEMP0)
ABS(X6:Y6) ABS(X5:Y5) ABS(X3:Y3) ABS(X2:Y2)

Figure 4-10. PSADBW Instruction Operation Using 64-bit Operands

Operation

PSADBW (when using 64-bit operands)

    TEMP0 ← ABS(DEST[7:0] − SRC[7:0]);
    (* Repeat operation for bytes 2 through 6 *)
    TEMP7 ← ABS(DEST[63:56] − SRC[63:56]);
    DEST[15:0] ← SUM(TEMP0:TEMP7);
    DEST[63:16] ← 000000000000H;

PSADBW (when using 128-bit operands)

    TEMP0 ← ABS(DEST[7:0] − SRC[7:0]);
    (* Repeat operation for bytes 2 through 14 *)
    TEMP15 ← ABS(DEST[127:120] − SRC[127:120]);
    DEST[15:0] ← SUM(TEMP0:TEMP7);
    DEST[63:16] ← 000000000000H;
    DEST[79:64] ← SUM(TEMP8:TEMP15);
    DEST[127:80] ← 000000000000H;
    DEST[VLMAX-1:128] (Unmodified)

VPSADBW (VEX.128 encoded version)

TEMP0 ← ABS(SRC1[7:0] - SRC2[7:0])
(* Repeat operation for bytes 2 through 14 *)
TEMP15 ← ABS(SRC1[127:120] - SRC2[127:120])
DEST[15:0] ←SUM(TEMP0:TEMP7)
DEST[63:16] ← 000000000000H
DEST[79:64] ← SUM(TEMP8:TEMP15)
DEST[127:80] ← 00000000000
DEST[VLMAX-1:128] ← 0

VPSADBW (VEX.256 encoded version)

TEMP0 ← ABS(SRC1[7:0] - SRC2[7:0])
(* Repeat operation for bytes 2 through 30*)
TEMP31 ← ABS(SRC1[255:248] - SRC2[255:248])
DEST[15:0] ←SUM(TEMP0:TEMP7)
DEST[63:16] ← 000000000000H
DEST[79:64] ← SUM(TEMP8:TEMP15)
DEST[127:80] ← 00000000000H
DEST[143:128] ←SUM(TEMP16:TEMP23)
DEST[191:144] ← 000000000000H
DEST[207:192] ← SUM(TEMP24:TEMP31)
DEST[223:208] ← 00000000000H

Intel C/C++ Compiler Intrinsic Equivalent

PSADBW:

__m64 _mm_sad_pu8(__m64 a,__m64 b)

(V)PSADBW:

__m128i _mm_sad_epu8(__m128i a, __m128i b)

VPSADBW:

__m256i _mm256_sad_epu8( __m256i a, __m256i b)

Flags Affected

None.

SIMD Floating-Point Exceptions

None.

Other Exceptions

See Exceptions Type 4; additionally

#UD If VEX.L = 1.