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VRSQRTE

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 ) .

A1

Decode for all variants of this encoding

if Q == '1' && (Vd[0] == '1' || Vm[0] == '1') then Undefined(); end; if (size == '01' && (!IsFeatureImplemented(FEAT_FP16) || F == '0')) || size IN {'00', '11'} then Undefined(); end; let floating_point : boolean = (F == '1'); let esize : integer{} = 8 << UInt(size); let elements : integer = 64 DIV esize; let d : integer = UInt(D::Vd); let m : integer = UInt(M::Vm); let regs : integer = if Q == '0' then 1 else 2;

T1

Decode for all variants of this encoding

if Q == '1' && (Vd[0] == '1' || Vm[0] == '1') then Undefined(); end; if size == '01' && (!IsFeatureImplemented(FEAT_FP16) || F == '0') then Undefined(); end; if size IN {'00', '11'} then Undefined(); end; if size == '01' && InITBlock() then UnpredictableProcedure(); end; let floating_point : boolean = (F == '1'); let esize : integer{} = 8 << UInt(size); let elements : integer = 64 DIV esize; let d : integer = UInt(D::Vd); let m : integer = UInt(M::Vm); let regs : integer = if Q == '0' then 1 else 2;

CONSTRAINED UNPREDICTABLE behavior

If size == '01' && InITBlock(), then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as if it passes the Condition code check.
• The instruction executes as NOP. This means it behaves as if it fails the Condition code check.