xssubqp

VSX Scalar Subtract Quad-Precision

xssubqp VRT,VRA,VRB
xssubqpo VRT,VRA,VRB

Subtracts the contents of two quad-precision floating-point registers and handles special cases like NaNs.

Details

Subtracts the quad-precision floating-point operand in VSR VRB from VSR VRA and stores the result in VSR VRT, handling infinities, NaNs, and denormalised numbers according to IEEE 754 semantics. This VSX instruction may update FPSCR exception flags and the result sign. The 'o' suffix variant enables underflow/overflow exception.

Pseudocode Operation

FRT ← FRA - FRB
FPSCR ← updated with exception flags (XX, ZX, UX, OX, VXISI, VXSNAN, etc.)

Programming Note

The xssubqp instruction is used for subtracting quad-precision floating-point numbers. Ensure that the VSX feature is enabled in the MSR register to avoid exceptions. Handle special cases like NaNs and infinities by checking the FPSCR flags after execution. The result is rounded according to the rounding mode specified in FPSCR.RN.

Example

xssubqp v1, v2, v3

Encoding

Binary Layout
63
0
FRT
6
FRA
11
FRB
16
514
21
Rc
31
 
Format X-form
Opcode 0xFC000408
Extension VSX
Registers Altered FPSCR FPRF FR FI FX VXSNAN VXISI OX UX XX

Operands

  • vD
    Target
  • vA
    Src A
  • vB
    Src B
  • VRT
    Target Vector-Scalar Register
  • VRA
    Source Vector-Scalar Register
  • VRB
    Source Vector-Scalar Register