fneg

Floating-Point Negate (Scalar)

FNEG <Hd|Sd|Dd>, <Hn|Sn|Dn>

Negates the value (flips sign bit).

Pseudocode Operation

if HaveFPExt() then
  Vd ← FPNeg(Vn)
else
  UNDEFINED

Example

FNEG Dd, Dn

Encoding

Binary Layout

0

31

0

30

0

29

11110

28:24

11

23:22

10000

21:17

10

16:15

10000

14:10

Rn

9:5

Rd

4:0

 

Format FP Data Processing

Opcode 0x1EE14000

Extension Floating Point

Operands

• Hd|Sd|Dd
  Destination SIMD&FP register (half, single or double-precision)
• Hn|Sn|Dn
  First source SIMD&FP register (half, single or double-precision)

Related

Other forms of fneg

• fneg SVE Floating-Point Negate
• fneg Vector Floating-Point Negate
• fneg Floating-Point Negate (Half-Precision)

More in Floating Point

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x2EF8F800	FNEG <Vd>.<T>, <Vn>.<T>		A64		0 | Q | 1 | 01110 | 1 | 111100 | 01111 | 10 | Rn | Rd
0x2EA0F800	FNEG <Vd>.<T>, <Vn>.<T>		A64		0 | Q | 1 | 011101 | sz | 10000 | 01111 | 10 | Rn | Rd
0x1EE14000	FNEG <Hd>, <Hn>		A64		0 | 0 | 0 | 11110 | 11 | 10000 | 10 | 10000 | Rn | Rd
0x1E214000	FNEG <Sd>, <Sn>		A64		0 | 0 | 0 | 11110 | 00 | 10000 | 10 | 10000 | Rn | Rd
0x1E614000	FNEG <Dd>, <Dn>		A64		0 | 0 | 0 | 11110 | 01 | 10000 | 10 | 10000 | Rn | Rd
0x041DA000	FNEG <Zd>.<T>, <Pg>/M, <Zn>.<T>		A64		00000100 | size | 011 | 10 | 1 | 101 | Pg | Zn | Zd

Description

Floating-point Negate (scalar). This instruction negates the value in the SIMD&FP source register and writes the result to the SIMD&FP destination register. Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

Operation

CheckFPEnabled64();

boolean merge = IsMerging(FPCR);
bits(128) result = if merge then V[d, 128] else 0<127:0>;

bits(esize) operand = V[n, esize];

Elem[result, 0, esize] = FPNeg(operand, FPCR);
V[d, 128] = result;