PM0214 datasheet(113/245 Pages) STMICROELECTRONICS

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PM0214

The STM32 Cortex-M4 instruction set

244

3.6.4

SMLAD

Signed multiply accumulate long dual

Syntax

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

;

where:

•

op is one of:

SMLAD: Signed multiply accumulate dual

SMLADX: Signed multiply accumulate dual reverse. X specifies which halfword of the

source register Rn is used as the multiply operand.

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

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

•

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

•

‘Rd’ is the destination register.

•

‘Rn’ is the first operand register holding the values to be multiplied

•

‘Rm’ is the second operand register

•

‘Ra’ is the accumulate value

Operation

The SMLAD and SMLADX instructions regard the two operands as four halfword 16-bit

values. The SMLAD and SMLADX instructions:

Either:

If X is not present, multiply the top signed halfword value in Rn with the top signed

halfword of Rm and the bottom signed halfword values in Rn with the bottom

signed halfword of Rm.

If X is present, multiply the top signed halfword value in Rn with the bottom signed

halfword of Rm and the bottom signed halfword values in Rn with the top signed

halfword of Rm.

Add both multiplication results to the signed 32-bit value in Ra.

Write the 32-bit signed result of the multiplication and addition to Rd.

Restrictions

Do not use SP or PC.

Condition flags

These instructions do not change the flags.

Examples

SMLAD

R10, R2, R1, R5 ; Multiplies two halfword values in R2 with

; corresponding halfwords in R1, adds R5 and writes

; to R10

SMLALDX R0, R2, R4, R6

; Multiplies top halfword of R2 with bottom halfword

; of R4, multiplies bottom halfword of R2 with top

; halfword of R4, adds R6 and writes to R0.

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