Multiply multiplies two register values. 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.
Optionally, it can update the condition flags based on the result. In the T32 instruction set, this option is limited to only a few forms of the instruction. Use of this option adversely affects performance on many implementations.
It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 and T2 ) .
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 | 0 | 0 | S | Rd | (0) | (0) | (0) | (0) | Rm | 1 | 0 | 0 | 1 | Rn | ||||||||||||
cond |
d = UInt(Rd); n = UInt(Rn); m = UInt(Rm); setflags = (S == '1'); if d == 15 || n == 15 || m == 15 then UNPREDICTABLE;
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | Rn | Rdm |
d = UInt(Rdm); n = UInt(Rn); m = UInt(Rdm); setflags = !InITBlock();
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 | 1 | 1 | 1 | 1 | Rd | 0 | 0 | 0 | 0 | Rm |
d = UInt(Rd); n = UInt(Rn); m = UInt(Rm); setflags = FALSE; if d == 15 || n == 15 || m == 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> |
<Rdm> |
Is the second general-purpose source register holding the multiplier and the destination register, encoded in the "Rdm" field. |
<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. If omitted, <Rd> is used. |
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 result = operand1 * operand2; R[d] = result<31:0>; if setflags then PSTATE.N = result<31>; PSTATE.Z = IsZeroBit(result<31:0>); // PSTATE.C, PSTATE.V unchanged
Internal version only: isa v00_79, pseudocode v34.2 ; Build timestamp: 2017-12-19T15:42
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