Rounding subtract narrow high part (bottom)
Subtract each vector element of the second source vector from the corresponding vector element in the first source vector, and place the most significant rounded half of the result in the even-numbered half-width destination elements, while setting the odd-numbered half-width destination elements to zero. This instruction is unpredicated.
| 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 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | size | 1 | Zm | 0 | 1 | 1 | 1 | 1 | 0 | Zn | Zd | |||||||||||||
| S | R | T | |||||||||||||||||||||||||||||
if !HaveSVE2() && !HaveSME() then UNDEFINED; if size == '00' then UNDEFINED; integer esize = 8 << UInt(size); integer n = UInt(Zn); integer m = UInt(Zm); integer d = UInt(Zd);
| <Zd> |
Is the name of the destination scalable vector register, encoded in the "Zd" field. |
| <T> |
Is the size specifier,
encoded in
|
| <Zn> |
Is the name of the first source scalable vector register, encoded in the "Zn" field. |
| <Tb> |
Is the size specifier,
encoded in
|
| <Zm> |
Is the name of the second source scalable vector register, encoded in the "Zm" field. |
CheckSVEEnabled(); integer elements = VL DIV esize; bits(VL) operand1 = Z[n]; bits(VL) operand2 = Z[m]; bits(VL) result; integer halfesize = esize DIV 2; integer round_const = 1 << (halfesize - 1); for e = 0 to elements-1 integer element1 = UInt(Elem[operand1, e, esize]); integer element2 = UInt(Elem[operand2, e, esize]); integer res = ((element1 - element2) + round_const) >> halfesize; Elem[result, 2*e + 0, halfesize] = res<halfesize-1:0>; Elem[result, 2*e + 1, halfesize] = Zeros(); Z[d] = result;
If FEAT_SVE2 is enabled or FEAT_SME is enabled, then when PSTATE.DIT is 1:
Internal version only: isa v33.11seprel, AdvSIMD v29.05, pseudocode v2021-09_rel, sve v2021-09_rc3d ; Build timestamp: 2021-10-06T11:41
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