ARM Compiler armasm User Guide : 13.129 SMMLS

13.129 SMMLS

Signed Most significant word Multiply with Subtraction.

Syntax

SMMLS{R}{cond} Rd, Rn, Rm, Ra

where:

R: is an optional parameter. If R is present, the result is rounded, otherwise it is truncated.
cond: is an optional condition code.
Rd: is the destination register.
Rn, Rm: are the registers holding the operands.
Ra: is a register holding the value to be added or subtracted from.

Operation

SMMLS multiplies the values from Rn and Rm, subtracts the product from the value in Ra shifted left by 32 bits, and stores the most significant 32 bits of the result in Rd.

If the optional R parameter is specified, 0x80000000 is added before extracting the most significant 32 bits. This has the effect of rounding the result.

Register restrictions

You cannot use PC for any operand.

You can use SP in A32 instructions but this is deprecated. You cannot use SP in T32 instructions.

Condition flags

This instruction does not change the flags.

Availability

The 32-bit instruction is available in A32 and T32.

For the ARMv7-M architecture, the 32-bit T32 instruction is only available in an ARMv7E-M implementation.

There is no 16-bit version of this instruction in T32.

Related reference

7.11 Condition code suffixes

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