vrecps

Vector Reciprocal Step

VRECPS<c>.F32 <Qd>, <Qn>, <Qm>

Newton-Raphson step for reciprocal refinement: (2 - Vn * Vm).

Pseudocode Operation

for i = 0 to 3
  Qd[i] ← 2.0 - (Qn[i] * Qm[i])

Example

VRECPS.F32 q0, q1, q2

Encoding

Binary Layout

1111001

31:25

0

24

0

23

D

22

0

21

sz

20

Vn

19:16

Vd

15:12

1111

11:8

N

7

0

6

M

5

1

4

Vm

3:0

 

Format NEON 3-Reg

Opcode 0xF2000F10

Extension NEON (SIMD)

Operands

• Qd
  Destination 128-bit SIMD register
• Qn
  First source 128-bit SIMD register
• Qm
  Second source 128-bit SIMD register

Related

More in NEON (SIMD)

Reference

View in Arm A64 ISA Reference ↗ Arm AArch32 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0xF2000F10	VRECPS{<c>}{<q>}.<dt> {<Dd>, }<Dn>, <Dm>		A32		1111001 | 0 | 0 | D | 0 | sz | Vn | Vd | 1111 | N | 0 | M | 1 | Vm
0xF2000F50	VRECPS{<c>}{<q>}.<dt> {<Qd>, }<Qn>, <Qm>		A32		1111001 | 0 | 0 | D | 0 | sz | Vn | Vd | 1111 | N | 1 | M | 1 | Vm
0xEF000F10	VRECPS{<c>}{<q>}.<dt> {<Dd>, }<Dn>, <Dm>		T32		111 | 0 | 11110 | D | 0 | sz | Vn | Vd | 1111 | N | 0 | M | 1 | Vm
0xEF000F50	VRECPS{<c>}{<q>}.<dt> {<Qd>, }<Qn>, <Qm>		T32		111 | 0 | 11110 | D | 0 | sz | Vn | Vd | 1111 | N | 1 | M | 1 | Vm

Description

Vector Reciprocal Step multiplies the elements of one vector by the corresponding elements of another vector, subtracts each of the products from 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.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();  CheckAdvSIMDEnabled();
    for r = 0 to regs-1
        for e = 0 to elements-1
            Elem[D[d+r],e,esize] = FPRecipStep(Elem[D[n+r],e,esize], Elem[D[m+r],e,esize]);