fnabs

Floating Negative Absolute Value

fnabs FRT, FRB

Computes negative absolute value of a float.

Encoding

Binary Layout

63

0:5

FRT

6:10

0

11:15

FRB

16:20

136

21:30

/

31

 

Format X-form

Opcode 0xFC000110

Extension Floating-Point

Operands

• FRT
  Target
• FRB
  Source

Example

fnabs 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 negative absolute value of a double-precision floating-point number in FRB and places the result in FRT. The sign bit is set to 1 while all other bits are taken from the absolute value. No exception flags are set.

Operation

FRT ← -abs(FRB)

Programming Note

The fnabs instruction is useful for converting a positive floating-point number to its negative counterpart while maintaining its magnitude. Ensure that the input register (FRB) contains a valid floating-point value; otherwise, the result may be undefined. This operation does not affect the FPSCR register, so no exception flags are set based on the input value.