vfnma

Vector Fused Negated Multiply Accumulate

VFNMA<c>.F32 <Sd>, <Sn>, <Sm>

Computes Vd = Vd - (Vn * Vm).

Pseudocode Operation

Sd ← round_to_nearest(Sd - (Sn × Sm))

Example

VFNMA.F32 s0, s1, s2

Encoding

Binary Layout

cond

31:28

1110

27:24

1

23

D

22

01

21:20

Vn

19:16

Vd

15:12

10

11:10

10

9:8

N

7

1

6

M

5

0

4

Vm

3:0

 

Format VFP Arith

Opcode 0x0E900A40

Extension VFPv4 (Float)

Operands

• Sd
  Destination 32-bit floating-point register
• Sn
  First source 32-bit floating-point register
• Sm
  Second source 32-bit floating-point register

Related

More in VFPv4 (Float)

Reference

View in Arm A64 ISA Reference ↗ Arm AArch32 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x0E900940	VFNMA{<c>}{<q>}.F16 <Sd>, <Sn>, <Sm>		A32		cond | 1110 | 1 | D | 01 | Vn | Vd | 10 | 01 | N | 1 | M | 0 | Vm
0x0E900A40	VFNMA{<c>}{<q>}.F32 <Sd>, <Sn>, <Sm>		A32		cond | 1110 | 1 | D | 01 | Vn | Vd | 10 | 10 | N | 1 | M | 0 | Vm
0x0E900B40	VFNMA{<c>}{<q>}.F64 <Dd>, <Dn>, <Dm>		A32		cond | 1110 | 1 | D | 01 | Vn | Vd | 10 | 11 | N | 1 | M | 0 | Vm
0xEE900940	VFNMA{<c>}{<q>}.F16 <Sd>, <Sn>, <Sm>		T32		11101110 | 1 | D | 01 | Vn | Vd | 10 | 01 | N | 1 | M | 0 | Vm
0xEE900A40	VFNMA{<c>}{<q>}.F32 <Sd>, <Sn>, <Sm>		T32		11101110 | 1 | D | 01 | Vn | Vd | 10 | 10 | N | 1 | M | 0 | Vm
0xEE900B40	VFNMA{<c>}{<q>}.F64 <Dd>, <Dn>, <Dm>		T32		11101110 | 1 | D | 01 | Vn | Vd | 10 | 11 | N | 1 | M | 0 | Vm

Description

Vector Fused Negate Multiply Accumulate negates one floating-point register value and multiplies it by another floating-point register value, adds the negation of the floating-point value in the destination register to the product, and writes the result back to the destination register. The instruction does not round the result of the multiply before the addition. Depending on settings in the CPACR, NSACR, HCPTR, and FPEXC 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(); CheckVFPEnabled(TRUE);
    case esize of
        when 16
            op16 = if op1_neg then FPNeg(S[n]<15:0>) else S[n]<15:0>;
            S[d] = Zeros(16) : FPMulAdd(FPNeg(S[d]<15:0>), op16, S[m]<15:0>, FPSCR[]);
        when 32
            op32 = if op1_neg then FPNeg(S[n]) else S[n];
            S[d] = FPMulAdd(FPNeg(S[d]), op32, S[m], FPSCR[]);
        when 64
            op64 = if op1_neg then FPNeg(D[n]) else D[n];
            D[d] = FPMulAdd(FPNeg(D[d]), op64, D[m], FPSCR[]);