frsqrte

Floating Reciprocal Square Root Estimate

frsqrte FRT,FRB

Estimates the reciprocal of the square root of a floating-point operand.

Encoding

Binary Layout

63

0:5

FRT

6:10

0

11:15

0

16:20

FRB

21:25

26

26:30

/

31

 

Format A-form

Opcode 0xFC000034

Extension Floating-Point

Operands

• FRT
  Target
• FRB
  Source

Example

frsqrte f1, f3

Registers Altered

FPSCR, CR1

Related

More in Floating-Point

Reference

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

Description

A estimate of the reciprocal of the square root of the floating-point operand in register FRB is placed into register FRT. The estimate placed into register FRT is correct to a precision of one part in 32 of the reciprocal of the square root of (FRB).

Operation

FRT ← estimate(1 / √FRB)

Programming Note

The frsqrte instruction provides a fast, approximate reciprocal square root calculation. It is useful for performance-critical applications where precision can be traded for speed. Ensure the input in FRB is positive to avoid undefined behavior. The result may need refinement for higher precision applications.