Rounding Subtract returning High Narrow. This instruction subtracts each vector element of the second source SIMD&FP register from the corresponding vector element of the first source SIMD&FP register, places the most significant half of the result into a vector, and writes the vector to the lower or upper half of the destination SIMD&FP register.
The results are rounded. For truncated results, see SUBHN.
The RSUBHN instruction writes the vector to the lower half of the destination register and clears the upper half, while the RSUBHN2 instruction writes the vector to the upper half of the destination register without affecting the other bits of the register.
Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.
| 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 |
| 0 | Q | 1 | 0 | 1 | 1 | 1 | 0 | size | 1 | Rm | 0 | 1 | 1 | 0 | 0 | 0 | Rn | Rd | |||||||||||||
| U | o1 | ||||||||||||||||||||||||||||||
integer d = UInt(Rd); integer n = UInt(Rn); integer m = UInt(Rm); if size == '11' then UNDEFINED; constant integer esize = 8 << UInt(size); constant integer datasize = 64; integer part = UInt(Q); integer elements = datasize DIV esize; boolean sub_op = (o1 == '1'); boolean round = (U == '1');
| <Vd> |
Is the name of the SIMD&FP destination register, encoded in the "Rd" field. |
| <Tb> |
Is an arrangement specifier,
encoded in
|
| <Vn> |
Is the name of the first SIMD&FP source register, encoded in the "Rn" field. |
| <Ta> |
Is an arrangement specifier,
encoded in
|
| <Vm> |
Is the name of the second SIMD&FP source register, encoded in the "Rm" field. |
CheckFPAdvSIMDEnabled64(); bits(2*datasize) operand1 = V[n, 2*datasize]; bits(2*datasize) operand2 = V[m, 2*datasize]; bits(datasize) result; integer element1; integer element2; integer sum; for e = 0 to elements-1 element1 = UInt(Elem[operand1, e, 2*esize]); element2 = UInt(Elem[operand2, e, 2*esize]); if sub_op then sum = element1 - element2; else sum = element1 + element2; sum = RShr(sum, esize, round); Elem[result, e, esize] = sum<esize-1:0>; Vpart[d, part, datasize] = result;
If PSTATE.DIT is 1:
Internal version only: aarchmrs v2023-12_rel, pseudocode v2023-12_rel, sve v2023-12_rel ; Build timestamp: 2023-12-15T16:46
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