dctfixq

Decimal Convert To Fixed Quad-Precision

dctfixq vD, vB

Converts 128-bit DFP to 64-bit integer.

Encoding

Binary Layout

63

0:5

vD

6:10

0

11:15

vB

16:20

290

21:30

/

31

 

Format X-form

Opcode 0xFC000244

Extension Decimal Floating-Point

Operands

• vD
  Target
• vB
  Source

Example

dctfixq vd, vb

Registers Altered

FPSCR

Related

More in Decimal Floating-Point

Reference

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

Description

Converts a 128-bit decimal floating-point number from vB into a 64-bit signed integer, storing the result in vD. The conversion rounds toward zero (truncates). If the DFP value is out of range for a 64-bit integer or is NaN, the result is undefined and FPSCR status flags may be set. The instruction is part of the Decimal Floating-Point extension.

Operation

vD ← ConvertToFixedDFP128(vB, FPSCR[RN])

Programming Note

The dctfixq instruction is used to convert a DFP Extended value to a 64-bit signed integer. It rounds the result and preserves the sign of the source operand. If the source is zero, the result is explicitly set to +0. This instruction operates at the FPSCR privilege level and may raise exceptions based on rounding modes or overflow conditions.