LDDQU (Load Unaligned Integer 128 Bits)

Opcodes

Opcode/Instruction Op/En 64/32-bit Mode CPUID Feature Flag Description
F2 0F F0 /r LDDQU xmm1, mem RM V/V SSE3 Load unaligned data from mem and return double quadword in xmm1.
VEX.128.F2.0F.WIG F0 /r VLDDQU xmm1, m128 RM V/V AVX Load unaligned packed integer values from mem to xmm1.
VEX.256.F2.0F.WIG F0 /r VLDDQU ymm1, m256 RM V/V AVX Load unaligned packed integer values from mem to ymm1.

Instruction Operand Encoding

Op/En Operand 1 Operand 2 Operand 3 Operand 4
RM ModRM:reg (w) ModRM:r/m (r) NA NA

Description

The instruction is functionally similar to (V)MOVDQU ymm/xmm, m256/m128 for loading from memory. That is: 32/16 bytes of data starting at an address specified by the source memory operand (second operand) are fetched from memory and placed in a destination register (first operand). The source operand need not be aligned on a 32/16-byte boundary. Up to 64/32 bytes may be loaded from memory; this is implementation dependent.

This instruction may improve performance relative to (V)MOVDQU if the source operand crosses a cache line boundary. In situations that require the data loaded by (V)LDDQU be modified and stored to the same location, use (V)MOVDQU or (V)MOVDQA instead of (V)LDDQU. To move a double quadword to or from memory locations that are known to be aligned on 16-byte boundaries, use the (V)MOVDQA instruction.

Implementation Notes

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

Note: In VEX-encoded versions, VEX.vvvv is reserved and must be 1111b otherwise instructions will #UD.

Operation

LDDQU (128-bit Legacy SSE version)

DEST[127:0] ← SRC[127:0]
DEST[VLMAX-1:128] (Unmodified)

VLDDQU (VEX.128 encoded version)

DEST[127:0] ← SRC[127:0]
DEST[VLMAX-1:128] ← 0

VLDDQU (VEX.256 encoded version)

DEST[255:0] ← SRC[255:0]

Intel C/C++ Compiler Intrinsic Equivalent

LDDQU:

__m128i _mm_lddqu_si128 (__m128i * p);

LDDQU:

__m256i _mm256_lddqu_si256 (__m256i * p);

Numeric Exceptions

None.

Other Exceptions

See Exceptions Type 4;

Note treatment of #AC varies.