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VRSQRTS

Vector Reciprocal Square Root Step multiplies the elements of one vector by the corresponding elements of another vector, subtracts each of the products from 3.0, divides these results by 2.0, and places the results into the elements of the destination vector.

The operand and result elements are floating-point numbers.

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' || Vn[0] == '1' || Vm[0] == '1') then Undefined(); end; if sz == '1' && !IsFeatureImplemented(FEAT_FP16) then Undefined(); end; let esize : integer{} = 32 >> UInt(sz); let elements : integer = 64 DIV esize; let d : integer = UInt(D::Vd); let n : integer = UInt(N::Vn); 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' || Vn[0] == '1' || Vm[0] == '1') then Undefined(); end; if sz == '1' && !IsFeatureImplemented(FEAT_FP16) then Undefined(); end; if sz == '1' && InITBlock() then UnpredictableProcedure(); end; let esize : integer{} = 32 >> UInt(sz); let elements : integer = 64 DIV esize; let d : integer = UInt(D::Vd); let n : integer = UInt(N::Vn); 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.