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AMD x86-64 Architecture Programmer's Manual, Volume 4, 128-Bit ...

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26568—Rev. 3.05—September 2003 <strong>AMD</strong><strong>64</strong> Technology<br />

PUNPCKLBW Unpack and Interleave Low Bytes<br />

Unpacks the low-order bytes from the first and second source operands and packs<br />

them into interleaved bytes in the destination (first source). The high-order bytes of<br />

the source operands are ignored. The first source/destination operand is an XMM<br />

register and the second source operand is another XMM register or <strong>128</strong>-bit memory<br />

location.<br />

Mnemonic Opcode Description<br />

PUNPCKLBW xmm1, xmm2/mem<strong>128</strong> 66 0F 60 /r Unpacks the eight low-order bytes in an XMM register and<br />

another XMM register or <strong>128</strong>-bit memory location and<br />

packs them into interleaved bytes in the destination XMM<br />

register.<br />

127 <strong>64</strong> 63 0<br />

If the second source operand is all 0s, the destination contains the bytes from the first<br />

source operand zero-extended to 16 bits. This operation is useful for expanding<br />

unsigned 8-bit values to unsigned 16-bit operands for subsequent processing that<br />

requires higher precision.<br />

Related Instructions<br />

xmm1 xmm2/mem<strong>128</strong><br />

127 <strong>64</strong> 63 0<br />

. . . . . .<br />

. . . . . .<br />

copy copy copy<br />

copy<br />

. . . . . . . . . . . .<br />

127 <strong>64</strong> 63<br />

0<br />

punpcklbw-<strong>128</strong>.eps<br />

PUNPCKHBW, PUNPCKHDQ, PUNPCKHQDQ, PUNPCKHWD, PUNPCKLDQ,<br />

PUNPCKLQDQ, PUNPCKLWD<br />

PUNPCKLBW 333

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