PM0214 datasheet(120/245 Pages) STMICROELECTRONICS

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The STM32 Cortex-M4 instruction set

PM0214

120/245

DocID022708 Rev 4

3.6.9

SMUAD and SMUSD

Signed dual multiply add and Signed dual multiply subtract

Syntax

op{X}{cond} Rd, Rn, Rm

where:

•

op is one of:

SMUAD: Signed dual multiply add.

SMUADX: Signed dual multiply add reversed.

SMUSD: Signed dual multiply subtract.

SMUSDX: Signed dual multiply subtract reversed.

–

If X is present, the multiplications are bottom × top and top × bottom.

If the X is omitted, the multiplications are bottom × bottom and top × top.

•

‘cond’ is an optional condition code (see Conditional execution on page 64)

•

‘Rd’ is the destination register.

•

‘Rn’, ‘Rm’ are registers holding the first and second operands

Operation

SMUAD interprets first and second operand values as two signed halfwords:

Optionally rotates the halfwords of the second operand.

Performs two signed 16 × 16-bit multiplications.

Adds the two multiplication results together.

Writes the result of the addition to the destination register.

SMUSD interprets the values from the first and second operands as two’s complement

signed integers:

Optionally rotates the halfwords of the second operand.

Performs two signed 16 × 16-bit multiplications.

Subtracts the result of the top halfword multiplication from the result of the bottom

halfword multiplication.

Writes the result of the subtraction to the destination register.

Restrictions

In these instructions: Do not use SP or PC.

Condition flags

Sets the Q flag if the addition overflows. The multiplications cannot overflow.

Examples

SMUAD

R0, R4, R5 ; Multiplies bottom halfword of R4 with the bottom

; halfword of R5, adds multiplication of top halfword

; of R4 with top halfword of R5, writes to R0

SMUADX

R3, R7, R4 ; Multiplies bottom halfword of R7 with top halfword

; of R4, adds multiplication of top halfword of R7

; with bottom halfword of R4, writes to R3

SMUSD

R3, R6, R2 ; Multiplies bottom halfword of R4 with bottom halfword

; of R6, subtracts multiplication of top halfword of R6

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