xsnmsubqp

VSX Scalar Negative Multiply-Subtract Quad-Precision

xsnmsubqp VRT,VRA,VRB

Performs a negative multiply-subtract operation on quad-precision floating-point values.

Encoding

Binary Layout

64

VRT

VRA

VRB

RO

 

Format X-form

Opcode 0xFC0003C8

Extension VSX

Operands

• VRT
  Target Vector Register
• VRA
  Source Vector Register
• VRB
  Source Vector Register

Example

xsnmsubqp v1, v2, v3

Registers Altered

FPSCR, VXSNAN, VXIMZ, Vxisi, OX, UX, XX, FPRF, FR, FI

Related

More in VSX

Reference

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

Description

Performs a scalar negative multiply-subtract operation on quad-precision floating-point values, computing VRT = -(VRA × VRB) - VRT. The result is rounded according to the current rounding mode in FPSCR. This instruction requires VSX support and updates FPSCR exception flags based on the operation result.

Operation

VRT[0:127] ← -(VRA[0:127] × VRB[0:127]) - VRT[0:127]
FPSCR ← update_exception_flags(FPSCR, result)

Programming Note

The xsnmsubqp instruction is used for performing a scalar negative multiply-subtract operation on quad-precision floating-point numbers. Ensure that the VSX (Vector Scalar Extensions) are enabled in the MSR register to avoid exceptions. Be cautious of potential overflow and underflow conditions, as indicated by the exception flags in FPSCR. The result is rounded using round-to-nearest mode by default.