Multiply and Subtract multiplies two register values, and subtracts the product from a third register value. The least significant 32 bits of the result are written to the destination register. These 32 bits do not depend on whether the source register values are considered to be signed values or unsigned values.
It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .
31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
!= 1111 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | Rd | Ra | Rm | 1 | 0 | 0 | 1 | Rn | |||||||||||||||
cond |
d = UInt(Rd); n = UInt(Rn); m = UInt(Rm); a = UInt(Ra); if d == 15 || n == 15 || m == 15 || a == 15 then UNPREDICTABLE;
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | Rn | Ra | Rd | 0 | 0 | 0 | 1 | Rm |
d = UInt(Rd); n = UInt(Rn); m = UInt(Rm); a = UInt(Ra); if d == 15 || n == 15 || m == 15 || a == 15 then UNPREDICTABLE; // ARMv8-A removes UNPREDICTABLE for R13
For more information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors.
<c> |
<q> |
<Rd> |
Is the general-purpose destination register, encoded in the "Rd" field. |
<Rn> |
Is the first general-purpose source register holding the multiplicand, encoded in the "Rn" field. |
<Rm> |
Is the second general-purpose source register holding the multiplier, encoded in the "Rm" field. |
<Ra> |
Is the third general-purpose source register holding the minuend, encoded in the "Ra" field. |
if ConditionPassed() then EncodingSpecificOperations(); operand1 = SInt(R[n]); // operand1 = UInt(R[n]) produces the same final results operand2 = SInt(R[m]); // operand2 = UInt(R[m]) produces the same final results addend = SInt(R[a]); // addend = UInt(R[a]) produces the same final results result = addend - operand1 * operand2; R[d] = result<31:0>;
Internal version only: isa v00_79, pseudocode v34.2 ; Build timestamp: 2017-12-19T15:42
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