abs

Vector Absolute Value

ABS <Vd>.<T>, <Vn>.<T>

Calculates absolute value of integer elements.

Pseudocode Operation

element_size ← 8 << size;
for i = 0 to (vector_length / element_size - 1)
  if Vn.<element_size>[i] == minimum_signed_value(element_size)
    Vd.<element_size>[i] ← minimum_signed_value(element_size);
  else
    Vd.<element_size>[i] ← |Vn.<element_size>[i]|;

Example

ABS v0.4s.T, v1.4s.T

Encoding

Binary Layout

01110

28:24

size

23:22

10000

21:17

01011

16:12

11:10

9:5

4:0

Format SIMD Two Register

Opcode 0x0E20B800

Extension NEON (SIMD)

Operands

Vd
Destination SIMD/FP vector register
Vn
First source SIMD/FP vector register

Other forms of abs

abs SVE Absolute Value

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction	ISA	Bit pattern
0x5AC02000	ABS <Wd>, <Wn>	A64	0 \| 1 \| 0 \| 11010110 \| 00000 \| 001000 \| Rn \| Rd
0xDAC02000	ABS <Xd>, <Xn>	A64	1 \| 1 \| 0 \| 11010110 \| 00000 \| 001000 \| Rn \| Rd
0x5EE0B800	ABS D<d>, D<n>	A64	01 \| 0 \| 11110 \| 11 \| 10000 \| 01011 \| 10 \| Rn \| Rd
0x0E20B800	ABS <Vd>.<T>, <Vn>.<T>	A64	0 \| Q \| 0 \| 01110 \| size \| 10000 \| 01011 \| 10 \| Rn \| Rd
0x0416A000	ABS <Zd>.<T>, <Pg>/M, <Zn>.<T>	A64	00000100 \| size \| 010 \| 11 \| 0 \| 101 \| Pg \| Zn \| Zd

Description

Absolute value (vector). This instruction calculates the absolute value of each vector element in the source SIMD&FP register, puts the result into a vector, and writes the vector to the destination SIMD&FP 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

CheckFPAdvSIMDEnabled64();
bits(datasize) operand = V[n, datasize];
bits(datasize) result;
integer element;

for e = 0 to elements-1
    element = SInt(Elem[operand, e, esize]);
    if neg then
        element = -element;
    else
        element = Abs(element);
    Elem[result, e, esize] = element<esize-1:0>;

V[d, datasize] = result;

abs