pg_0545

Index

3-505

INSTRUCTION SET REFERENCE

PMADDWDPacked Multiply and Add

Description

This instruction multiplies the individual signed words of the destination operand by the corre-

sponding signed words of the source operand, producing four signed, doubleword results (refer

to Figure 3-65). The two doubleword results from the multiplication of the high-order words are

added together and stored in the upper doubleword of the destination operand; the two double-

word results from the multiplication of the low-order words are added together and stored in the

lower doubleword of the destination operand. The destination operand must be an MMX tech-

nology register; the source operand may be either an MMX technology register or a 64-bit

memory location.

The PMADDWD instruction wraps around to 80000000H only when all four words of both the

source and destination operands are 8000H.

Operation

DEST(31..0)

(DEST(15..0)

SRC(15..0)) + (DEST(31..16)

SRC(31..16));

DEST(63..32)

(DEST(47..32)

SRC(47..32)) + (DEST(63..48)

SRC(63..48));

Opcode

Instruction

Description

0F F5 /r

PMADDWD mm,

mm/m64

Multiply the packed words in mm by the packed

words in mm/m64. Add the 32-bit pairs of results

and store in mm as doubleword

Figure 3-65. Operation of the PMADDWD Instruction

0111000111000111

10000000000000000000010000000000

11001000111000111001110000000000

PMADDWD mm, mm/m64

mm/m64

Index