x86 Instruction Set Reference

PSLLDQ - Shift Double Quadword Left Logical

Opcode Mnemonic Description
66 0F 73 /7 ib PSLLDQ xmm1, imm8 Shift xmm1 left by imm8 bytes while shifting in 0s.
Description

Shifts the destination operand (first operand) to the left by the number of bytes specified in the count operand (second operand). The empty low-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 destination operand is an XMM register. The count operand is an 8-bit immediate.
Operation 
Temporary = Count;
if(Temporary > 15) Temporary = 16;
Destination = Destination << (Temporary * 8);
Flags affected

None.

Instruction Latency Throughput Execution Unit
CPUID0F3n/0F2n/069n0F3n/0F2n/069n0F2n
PSLLDQ xmm, imm84/4/42/2/4MMX_SHFT