fsel

Floating Select

fsel FRT,FRA,FRC,FRB

Selects FRA if FRC >= 0, else FRB (Optional).

Encoding

Binary Layout

63

0:5

FRT

6:10

FRA

11:15

FRB

16:20

FRC

21:25

23

26:30

/

31

 

Format A-form

Opcode 0xFC00002E

Extension Floating-Point

Operands

• FRT
  Target
• FRA
  True
• FRC
  Cond
• FRB
  False

Example

fsel f1, f2, f4, f3

Registers Altered

CR1, FPSCR

Related

More in Floating-Point

Reference

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

Description

Selects between FRA and FRB based on the sign of FRC: if FRC ≥ 0, the result is FRA; otherwise, the result is FRB. The optional dot (.) form sets CR1 based on the result's FPRF. This is an optional category instruction.

Operation

if FRC ≥ 0.0 then
  FRT ← FRA
else
  FRT ← FRB
if Rc = 1 then CR1 ← FPRF(FRT)

Programming Note

Warning: Care must be taken in using fsel if IEEE compatibility is required, or if the values being tested can be NaNs or infinities.