Revision as of 19:55, 28 November 2011
|ARM family||All (except ARMv1)|
MLA is used to multiply registers (signed or unsigned) to create a 32 bit result, which is then added to another value, which produces the final result.
Operand 2 is multiplied by operand 3, the value of operand 4 is added, and the result is stored in operand 1. All operands are registers.
If the S bit is specified, the flags are N, Z, and C flags are updated as follows: N is the result bit 31, Z is set if the result is zero, and C is undefined. V is not updated.
There is also a Multiply instruction for basic multiplication.
MLA <op 1>, <op 2>, <op 3>, <op 4>
op_1 = (op_2 × op_3) + op_4
MOV R1, #5 MOV R2, #3 MOV R3, #18 MLA R0, R1, R2, R3 ; R0 now equals 33
- You cannot specify R15 for any of the operands.
- Having operand 1 and operand 2 be the same register is unpredicable, thus, for example, the following cannot be used:
MLA R0, R0, R1, R2
- MLA provides the lower 32 bits of a 64 bit product, therefore the result is the same for both signed and unsigned values.
The instruction bit pattern is as follows:
|31 - 28||27 - 21||20||19 - 16||15 - 12||11 - 8||7 - 4||3 - 0|
|condition||0 0 0 0 0 0 1||S||op_1||op_4||op_3||1 0 0 1||op_2|