Vector Reciprocal Square Root Estimate finds an approximate reciprocal square root of each element in a vector, and places the results in a second vector.
The operand and result elements are the same type, and can be floating-point numbers or unsigned integers.
For details of the operation performed by this instruction see Floating-point reciprocal estimate and step.
Depending on settings in the CPACR, NSACR, and HCPTR registers, and the Security state and PE mode in which the instruction is executed, an attempt to execute the instruction might be undefined, or trapped to Hyp mode. For more information see Enabling Advanced SIMD and floating-point support.
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 |
| 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | D | 1 | 1 | size | 1 | 1 | Vd | 0 | 1 | 0 | F | 1 | Q | M | 0 | Vm | |||||||
if Q == '1' && (Vd<0> == '1' || Vm<0> == '1') then UNDEFINED; if (size == '01' && (!HaveFP16Ext() || F == '0')) || size IN {'00', '11'} then UNDEFINED; floating_point = (F == '1'); integer esize; integer elements; case size of when '01' esize = 16; elements = 4; when '10' esize = 32; elements = 2; d = UInt(D:Vd); m = UInt(M:Vm); regs = if Q == '0' then 1 else 2;
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| 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | D | 1 | 1 | size | 1 | 1 | Vd | 0 | 1 | 0 | F | 1 | Q | M | 0 | Vm | |||||||
if Q == '1' && (Vd<0> == '1' || Vm<0> == '1') then UNDEFINED; if (size == '01' && (!HaveFP16Ext() || F == '0')) || size IN {'00', '11'} then UNDEFINED; if size == '01' && InITBlock() then UNPREDICTABLE; floating_point = (F == '1'); integer esize; integer elements; case size of when '01' esize = 16; elements = 4; when '10' esize = 32; elements = 2; d = UInt(D:Vd); m = UInt(M:Vm); regs = if Q == '0' then 1 else 2;
If size == '01' && InITBlock(), then one of the following behaviors must occur:
| <c> |
For encoding A1: see Standard assembler syntax fields. This encoding must be unconditional. |
|
For encoding T1: see Standard assembler syntax fields. |
| <q> |
| <dt> |
Is the data type for the elements of the vectors,
encoded in
|
| <Qd> |
Is the 128-bit name of the SIMD&FP destination register, encoded in the "D:Vd" field as <Qd>*2. |
| <Qm> |
Is the 128-bit name of the SIMD&FP source register, encoded in the "M:Vm" field as <Qm>*2. |
| <Dd> |
Is the 64-bit name of the SIMD&FP destination register, encoded in the "D:Vd" field. |
| <Dm> |
Is the 64-bit name of the SIMD&FP source register, encoded in the "M:Vm" field. |
Newton-Raphson iteration
For details of the operation performed and how it can be used in a Newton-Raphson iteration to calculate the reciprocal of the square root of a number, see Floating-point reciprocal estimate and step.
if ConditionPassed() then EncodingSpecificOperations(); CheckAdvSIMDEnabled(); for r = 0 to regs-1 for e = 0 to elements-1 if floating_point then Elem[D[d+r],e,esize] = FPRSqrtEstimate(Elem[D[m+r],e,esize], StandardFPSCRValue()); else Elem[D[d+r],e,esize] = UnsignedRSqrtEstimate(Elem[D[m+r],e,esize]);
Internal version only: isa v01_31, pseudocode v2023-06_rel, sve v2023-06_rel ; Build timestamp: 2023-07-04T18:06
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