PSRLDQ (Shift Double Quadword Right Logical)

Opcodes

Opcode/Instruction Op/En 64/32 bit Mode Support CPUID Feature Flag Description
66 0F 73 /3 ib PSRLDQ xmm1, imm8 MI V/V SSE2 Shift xmm1 right by imm8 while shifting in 0s.
VEX.NDD.128.66.0F.WIG 73 /3 ib VPSRLDQ xmm1, xmm2, imm8 VMI V/V AVX Shift xmm2 right by imm8 bytes while shifting in 0s.
VEX.NDD.256.66.0F.WIG 73 /3 ib VPSRLDQ ymm1, ymm2, imm8 VMI V/V AVX2 Shift ymm1 right by imm8 bytes while shifting in 0s.

Instruction Operand Encoding

Op/En Operand 1 Operand 2 Operand 3 Operand 4
MI ModRM:r/m (r, w) imm8 NA NA
VMI VEX.vvvv (w) ModRM:r/m (r) imm8 NA

Description

Shifts the destination operand (first operand) to the right by the number of bytes specified in the count operand (second operand). The empty high-order bytes are cleared (set to all 0s). If the value specified by the count operand is greater than 15, the destination operand is set to all 0s. The count operand is an 8-bit immediate.

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

128-bit Legacy SSE version: The source and destination operands are the same. Bits (VLMAX-1:128) of the corre-sponding YMM destination register remain unchanged.

VEX.128 encoded version: The source and destination operands are XMM registers. Bits (VLMAX-1:128) of the destination YMM register are zeroed.

VEX.256 encoded version: The source operand is a YMM register. The destination operand is a YMM register. The count operand applies to both the low and high 128-bit lanes.

Note: VEX.vvvv encodes the destination register, and VEX.B + ModRM.r/m encodes the source register. VEX.L must be 0, otherwise instructions will #UD.

Operation

PSRLDQ(128-bit Legacy SSE version)

TEMP ← COUNT
IF (TEMP 
 15) THEN TEMP ← 16; FI
DEST ← DEST 
 (TEMP * 8)
DEST[VLMAX-1:128] (Unmodified)

VPSRLDQ (VEX.128 encoded version)

TEMP ← COUNT
IF (TEMP 
 15) THEN TEMP ← 16; FI
DEST ← SRC 
 (TEMP * 8)
DEST[VLMAX-1:128] ← 0

VPSRLDQ (VEX.256 encoded version)

TEMP ← COUNT
IF (TEMP 
 15) THEN TEMP ← 16; FI
DEST[127:0] ← SRC[127:0] 
 (TEMP * 8)
DEST[255:128] ← SRC[255:128] 
 (TEMP * 8)

Intel C/C++ Compiler Intrinsic Equivalents

(V)PSRLDQ:

__m128i _mm_srli_si128 ( __m128i a, int imm)

VPSRLDQ:

__m256i _mm256_srli_si256 ( __m256i a, const int imm)

Flags Affected

None.

Numeric Exceptions

None.

Other Exceptions

See Exceptions Type 7; additionally

#UD If VEX.L = 1.