Unsigned saturating subtract immediate (unpredicated)
Unsigned saturating subtract an unsigned immediate from each element of the source vector, and destructively place the results in the corresponding elements of the source vector. Each result element is saturated to the N-bit element's unsigned integer range 0 to (2N)-1. This instruction is unpredicated.
The immediate is an unsigned value in the range 0 to 255, and for element widths of 16 bits or higher it may also be a positive multiple of 256 in the range 256 to 65280.
The immediate is encoded in 8 bits with an optional left shift by 8. The preferred disassembly when the shift option is specified is "#<uimm8>, LSL #8". However an assembler and disassembler may also allow use of the shifted 16-bit value unless the immediate is 0 and the shift amount is 8, which must be unambiguously described as "#0, LSL #8".
| 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 | 0 | 1 | 0 | 0 | 1 | 0 | 1 | size | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | sh | imm8 | Zdn | ||||||||||||
| U | |||||||||||||||||||||||||||||||
if !HaveSVE() && !HaveSME() then UNDEFINED; if size:sh == '001' then UNDEFINED; constant integer esize = 8 << UInt(size); integer dn = UInt(Zdn); integer imm = UInt(imm8); if sh == '1' then imm = imm << 8; boolean unsigned = TRUE;
| <Zdn> |
Is the name of the source and destination scalable vector register, encoded in the "Zdn" field. |
| <T> |
Is the size specifier,
encoded in
|
| <imm> |
Is an unsigned immediate in the range 0 to 255, encoded in the "imm8" field. |
| <shift> |
Is the optional left shift to apply to the immediate, defaulting to LSL #0 and
encoded in
|
CheckSVEEnabled(); constant integer VL = CurrentVL; constant integer elements = VL DIV esize; bits(VL) operand1 = Z[dn, VL]; bits(VL) result; for e = 0 to elements-1 integer element1 = Int(Elem[operand1, e, esize], unsigned); (Elem[result, e, esize], -) = SatQ(element1 - imm, esize, unsigned); Z[dn, VL] = result;
This instruction might be immediately preceded in program order by a MOVPRFX instruction. The MOVPRFX instruction must conform to all of the following requirements, otherwise the behavior of the MOVPRFX and this instruction is unpredictable:
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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