pg_0533

Index

3-493

INSTRUCTION SET REFERENCE

PCMPEQB/PCMPEQW/PCMPEQDPacked Compare for Equal

Description

These instructions compare the individual data elements (bytes, words, or doublewords) in the

destination operand (first operand) to the corresponding data elements in the source operand

(second operand) (refer to Figure 3-61). If a pair of data elements are equal, the corresponding

data element in the destination operand is set to all ones; otherwise, it is set to all zeroes. The

destination operand must be an MMX technology register; the source operand may be either

an MMX technology register or a 64-bit memory location.

The PCMPEQB instruction compares the bytes in the destination operand to the corresponding

bytes in the source operand, with the bytes in the destination operand being set according to the

results.

The PCMPEQW instruction compares the words in the destination operand to the corresponding

words in the source operand, with the words in the destination operand being set according to

the results.

The PCMPEQD instruction compares the doublewords in the destination operand to the corre-

sponding doublewords in the source operand, with the doublewords in the destination operand

being set according to the results.

OpcodeInstruction

Description

0F 74 /rPCMPEQB mm, mm/m64Compare packed bytes in mm/m64 with packed bytes in mm

for equality.

0F 75 /rPCMPEQW mm, mm/m64Compare packed words in mm/m64 with packed words in

mm for equality.

0F 76 /rPCMPEQD mm, mm/m64Compare packed doublewords in mm/m64 with packed

doublewords in mm for equality.

Figure 3-61. Operation of the PCMPEQW Instruction

PCMPEQW mm, mm/m64

mm/m64

0000000000000000

1111111111111111

0000000000000001

0000000000000000

0000000000000111

0111000111000111

0000000000000000

0111000111000111

1111111111111111

True

False

3006020

Index