fabs

Floating Absolute Value

fabs FRT, FRB

Computes absolute value of a float.

Encoding

Binary Layout

63

0:5

FRT

6:10

0

11:15

FRB

16:20

264

21:30

/

31

 

Format X-form

Opcode 0xFC000210

Extension Floating-Point

Operands

• FRT
  Target
• FRB
  Source

Example

fabs f1, f3

Registers Altered

FPSCR

Related

More in Floating-Point

Reference

View in PowerISA v3.1C Specification ↗ OPF Power ISA v3.1C

Description

Computes the absolute value of a double-precision floating-point number in FRB and places the result in FRT. The sign bit is cleared while all other bits remain unchanged. No exception flags are set.

Operation

FRT ← abs(FRB)

Programming Note

The fabs instruction is commonly used when you need to ensure that a floating-point number is positive without altering its magnitude. Be cautious with NaN (Not-a-Number) values, as fabs will return a quiet NaN if the input is a signaling NaN. This instruction operates at user privilege level and does not raise exceptions for normal inputs; however, it respects the rounding mode set in the FPSCR register.