fabs

SVE Floating-Point Absolute Value

FABS <Zdn>.<T>, <Pg>/M, <Zdn>.<T>

Calculates absolute value of floats.

Pseudocode Operation

for i = 0 to VL-1
  if Pg[i] == '1' then
    Zdn[i] ← FPAbs(Zdn[i])
  // else Zdn[i] unchanged

Example

FABS z0.s.T, p0/m/M, z0.s.T

Encoding

Binary Layout

00000100

31:24

size

23:22

011

21:19

10

18:17

0

16

101

15:13

Pg

12:10

Zn

9:5

Zd

4:0

 

Format SVE FP Unary

Opcode 0x041CA000

Extension SVE

Operands

• Zdn
  Combined destination/source scalable vector register (SVE)
• Pg
  Mask

Related

Other forms of fabs

• fabs Floating-Point Absolute Value (Scalar)
• fabs Vector Floating-Point Absolute Value
• fabs Floating-Point Absolute Value (Half-Precision)

More in SVE

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x0EF8F800	FABS <Vd>.<T>, <Vn>.<T>		A64		0 | Q | 0 | 01110 | 1 | 111100 | 01111 | 10 | Rn | Rd
0x0EA0F800	FABS <Vd>.<T>, <Vn>.<T>		A64		0 | Q | 0 | 011101 | sz | 10000 | 01111 | 10 | Rn | Rd
0x1EE0C000	FABS <Hd>, <Hn>		A64		0 | 0 | 0 | 11110 | 11 | 10000 | 01 | 10000 | Rn | Rd
0x1E20C000	FABS <Sd>, <Sn>		A64		0 | 0 | 0 | 11110 | 00 | 10000 | 01 | 10000 | Rn | Rd
0x1E60C000	FABS <Dd>, <Dn>		A64		0 | 0 | 0 | 11110 | 01 | 10000 | 01 | 10000 | Rn | Rd
0x041CA000	FABS <Zd>.<T>, <Pg>/M, <Zn>.<T>		A64		00000100 | size | 011 | 10 | 0 | 101 | Pg | Zn | Zd

Description

Take the absolute value of each active floating-point element of the source vector, and place the results in the corresponding elements of the destination vector. This clears the sign bit and cannot signal a floating-point exception. Inactive elements in the destination vector register remain unmodified.

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
bits(PL) mask = P[g, PL];
bits(VL) operand = if AnyActiveElement(mask, esize) then Z[n, VL] else Zeros(VL);
bits(VL) result = Z[d, VL];

for e = 0 to elements-1
    if ActivePredicateElement(mask, e, esize) then
        bits(esize) element = Elem[operand, e, esize];
        Elem[result, e, esize] = FPAbs(element, FPCR);

Z[d, VL] = result;