Shift right and insert (immediate)
This instruction reads each vector element in the source SIMD&FP register, right shifts each vector element by an immediate value, and inserts the result into the corresponding vector element in the destination SIMD&FP register such that the new zero bits created by the shift are not inserted but retain their existing value. Bits shifted out of the right of each vector element of the source register are lost.
The following figure shows an example of the operation of shift right by 3 for an 8-bit vector element.
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.
It has encodings from 2 classes: Scalar and Vector
| 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 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | x | x | x | immb | 0 | 1 | 0 | 0 | 0 | 1 | Rn | Rd | ||||||||||
| U | immh | opcode | |||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF); end; if immh[3] != '1' then EndOfDecode(Decode_UNDEF); end; let d : integer{} = UInt(Rd); let n : integer{} = UInt(Rn); let esize : integer{} = 8 << 3; let datasize : integer{} = esize; let elements : integer = 1; let shift : integer = (esize * 2) - UInt(immh::immb);
| 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 | 1 | 0 | != 0000 | immb | 0 | 1 | 0 | 0 | 0 | 1 | Rn | Rd | |||||||||||||
| U | immh | opcode | |||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF); end; if immh[3]::Q == '10' then EndOfDecode(Decode_UNDEF); end; let d : integer{} = UInt(Rd); let n : integer{} = UInt(Rn); let esize : integer{} = 8 << HighestSetBitNZ(immh); let datasize : integer{} = 64 << UInt(Q); let elements : integer = datasize DIV esize; let shift : integer = (esize * 2) - UInt(immh::immb);
| <d> |
Is the number of the SIMD&FP destination register, encoded in the "Rd" field. |
| <n> |
Is the number of the SIMD&FP source register, encoded in the "Rn" field. |
| <Vd> |
Is the name of the SIMD&FP destination register, encoded in the "Rd" field. |
| <T> |
Is an arrangement specifier,
encoded in
|
| <Vn> |
Is the name of the SIMD&FP source register, encoded in the "Rn" field. |
AArch64_CheckFPAdvSIMDEnabled(); let operand : bits(datasize) = V{}(n); let operand2 : bits(datasize) = V{}(d); let mask : bits(esize) = LSR(Ones{esize}, shift); var result : bits(datasize); var shifted : bits(esize); for e = 0 to elements-1 do shifted = LSR(operand[e*:esize], shift); result[e*:esize] = (operand2[e*:esize] AND NOT(mask)) OR shifted; end; V{datasize}(d) = result;
This instruction is a data-independent-time instruction as described in About PSTATE.DIT.
2026-03_rel 2026-03-26 20:48:11
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