Signed Most Significant Word Multiply multiplies two signed 32-bit values, extracts the most significant 32 bits of the result, and writes those bits to the destination register.
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 | 1 | 1 | 1 | 1 | Rm | 0 | 0 | R | 1 | Rn | ||||||||||||
cond |
d = UInt(Rd); n = UInt(Rn); m = UInt(Rm); 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 | 1 | 1 | 1 | 1 | Rd | 0 | 0 | 0 | R | Rm |
d = UInt(Rd); n = UInt(Rn); m = UInt(Rm); round = (R == '1'); 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> |
<Rd> |
Is the general-purpose destination register, encoded in the "Rd" field. |
<Rn> |
Is the first general-purpose source register, encoded in the "Rn" field. |
<Rm> |
Is the second general-purpose source register, encoded in the "Rm" field. |
if ConditionPassed() then EncodingSpecificOperations(); result = SInt(R[n]) * SInt(R[m]); if round then result = result + 0x80000000; R[d] = result<63:32>;
Internal version only: isa v00_81, pseudocode v34.2.2 ; Build timestamp: 2018-03-28T20:43
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