xsresp

VSX Scalar Reciprocal Estimate Single-Precision

xsresp XT,XB

Estimates the reciprocal of a single-precision floating-point value.

Encoding

Binary Layout

T

6:10

B

11:15

26

16:20

BX

21:29

TX

30:31

 

Format XX2-form

Opcode 0xF0000068

Extension VSX

Operands

• XT
  Target Vector-Scalar Register
• XB
  Source Vector-Scalar Register

Example

xsresp vs1, vs3

Registers Altered

FPSCR, VXSNAN

Related

More in VSX

Reference

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

Description

Computes an estimate of the reciprocal (1/XB) for a single-precision floating-point scalar value, placing the result in XT. The estimate is accurate to about 7 bits of precision. This instruction requires VSX support and may update FPSCR exception flags if the source is invalid or zero.

Operation

XT[32:63] ← reciprocal_estimate(XB[32:63])
FPSCR ← update_exception_flags(FPSCR, result)

Programming Note

Previous versions of the architecture allowed the contents of doubleword 1 of the result register to be undefined. However, all processors that support this instruction write 0s into doubleword 1 of the result register.