nmacchw

Negative Multiply Accumulate Cross Halfword

nmacchw RT, RA, RB

Negate product of cross halfwords and add to accumulator.

Encoding

Binary Layout

4

0:5

RT

6:10

RA

11:15

RB

16:20

174

21:30

0

31

 

Format XO-form

Opcode 0x1000015C

Extension Embedded

Operands

• RT
  Acc/Dest
• RA
  Src A
• RB
  Src B

Example

nmacchw r3, r4, r5

Related

More in Embedded

Reference

View in PowerISA v3.1C Specification ↗ OPF Power ISA v3.1C

Description

Multiplies the sign-extended bottom halfword of RA by the sign-extended top halfword of RB, negates the product, and adds it to the current value of RT (treating RT as a 32-bit accumulator). The result is stored back in RT. No condition register or status flags are affected.

Operation

a ← EXTS(RA[16:31])
b ← EXTS(RB[0:15])
product ← (a × b)[32:63]
RT ← RT + (¬product + 1)