dxexq

Decimal Extract Exponent Quad-Precision

dxexq vD, vB

Extracts exponent from 128-bit DFP.

Encoding

Binary Layout

63

0:5

vD

6:10

0

11:15

vB

16:20

354

21:30

/

31

 

Format X-form

Opcode 0xFC0002C4

Extension Decimal Floating-Point

Operands

• vD
  Target
• vB
  Source

Example

dxexq vd, vb

Registers Altered

FPSCR

Related

More in Decimal Floating-Point

Reference

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

Description

Extracts the exponent field from a 128-bit decimal floating-point number in vB and stores it as a 64-bit signed integer in vD. For normal numbers, the result is the biased exponent; for special values (zero, infinity, NaN), the result follows the DFP specification. The instruction is part of the Decimal Floating-Point extension.

Operation

vD ← ExponentExtractDFP128(vB)

Programming Note

The dxexq instruction is used to extract the biased exponent from a quad-precision decimal floating-point number. Ensure the source operand is properly aligned, as misalignment can lead to exceptions. This operation requires FPSCR (Floating Point Status and Control Register) to be correctly set for proper rounding modes and exception handling.