Signed Most Significant Word Multiply Accumulate multiplies two signed 32-bit values, extracts the most significant 32 bits of the result, and adds an accumulate value.
Optionally, the instruction can specify that the result is rounded instead of being truncated. In this case, the constant 0x80000000 is added to the product before the high word is extracted.
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 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | Rd | != 1111 | Rm | 0 | 0 | R | 1 | Rn | |||||||||||||||
| cond | Ra | ||||||||||||||||||||||||||||||
if Ra == '1111' then SEE "SMMUL"; constant d = UInt(Rd); constant n = UInt(Rn); constant m = UInt(Rm); constant a = UInt(Ra); constant round = (R == '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 | 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 | 1 | 0 | 1 | Rn | != 1111 | Rd | 0 | 0 | 0 | R | Rm | ||||||||||||
| Ra | |||||||||||||||||||||||||||||||
if Ra == '1111' then SEE "SMMUL"; constant d = UInt(Rd); constant n = UInt(Rn); constant m = UInt(Rm); constant a = UInt(Ra); constant round = (R == '1'); // Armv8-A removes UNPREDICTABLE for R13 if d == 15 || n == 15 || m == 15 then UNPREDICTABLE;
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 addend, encoded in the "Ra" field. |
if ConditionPassed() then EncodingSpecificOperations(); result = (SInt(R[a]) << 32) + SInt(R[n]) * SInt(R[m]); if round then result = result + 0x80000000; R[d] = result<63:32>;
If CPSR.DIT is 1, this instruction has passed its condition execution check, and does not use R15 as either its source or destination:
Internal version only: isa v01_31, pseudocode v2024-03_rel ; Build timestamp: 2024-03-25T10:05
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