RealView Compilation Tools Assembler Guide: 4.4.7. SMMUL, SMMLA, and SMMLS

4.4.7. SMMUL, SMMLA, and SMMLS

Signed Most significant word Multiply, Signed Most significant word Multiply with Accumulation, and Signed Most significant word Multiply with Subtraction. These instructions have 32-bit operands and produce only the most significant 32-bits of the result.

Syntax

SMMUL{R}{cond} {Rd}, Rn, Rm

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

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 (see Conditional execution).
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.

Do not use r15 for any of Rd, Rn, Rm, or Ra.

Operation

SMMUL multiplies the values from Rn and Rm, and stores the most significant 32 bits of the 64-bit result to Rd.

SMMLA multiplies the values from Rn and Rm, adds the value in Ra to the most significant 32 bits of the product, and stores the result in Rd.

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.

Condition flags

These instructions do not change the flags.

Architectures

These ARM instructions are available in ARMv6 and above.

These 32-bit Thumb instructions are available in ARMv6T2 and above, except the ARMv7-M profile.

There are no 16-bit Thumb versions of these instructions.

Examples

    SMMULGE     r6, r4, r3
    SMMULR      r2, r2, r2

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