frsqrtes

Floating Reciprocal Square Root Estimate Single

frsqrtes FRT, FRB

Estimates 1/sqrt(x) (Single Precision).

Encoding

Binary Layout

59

0:5

FRT

6:10

0

11:15

0

16:20

FRB

21:25

26

26:30

/

31

 

Format A-form

Opcode 0xEC000034

Extension Floating-Point

Operands

• FRT
  Target
• FRB
  Source

Example

frsqrtes f1, f3

Registers Altered

FPSCR

Related

More in Floating-Point

Reference

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

Description

Computes an estimate of the reciprocal of the square root (1/sqrt(x)) of the single-precision floating-point value in FRB and stores the result in FRT. The estimate is accurate to approximately 1 part in 256 for normalized positive values. If Rc=1, CR1 is set based on the result; FPSCR exception bits are set according to floating-point exception enable controls.

Operation

FRT ← estimate(1.0 / sqrt(FRB))
if Rc = 1 then
  CR1 ← (FRT_exception_summary)

Programming Note

The frsqrtes instruction provides a fast estimate of the reciprocal square root, suitable for performance-critical applications where precision is less critical than speed. Be aware that it may raise exceptions for special values like NaN or infinity, and results are only accurate to within one part in 32 of the true value.