xscmpgtqp

VSX Scalar Compare Greater Than Quad-Precision X-form

xscmpgtqp VRT,VRA,VRB

Compares two quad-precision floating-point values and sets the target vector register to all 1s if the first value is greater than the second, otherwise all 0s.

Encoding

Binary Layout

0:5

VRT

6:10

VRA

11:15

VRB

16:31

Format X-form

Opcode 0xFC0001C8

Extension VSX

Operands

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

Example

xscmpgtqp v1, v2, v3

Registers Altered

FPSCR, VXSNAN, VXVC

Reference

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

Description

The instruction compares the contents of VSR[VRA+32] (src1) with the contents of VSR[VRB+32] (src2). If src1 is greater than src2, VSR[VRT+32] is set to all 1s; otherwise, it is set to all 0s. NaN comparisons result in false for the predicate.

Operation

if MSR.VSX=0 then VSX_Unavailable()
src1 ←bfp_CONVERT_FROM_BFP128(VSR[VRA+32])
src2 ←bfp_CONVERT_FROM_BFP128(VSR[VRB+32])
vxsnan_flag ←0b0
vxvc_flag ←src1.class.QNaN | src2.class.QNaN
vex_flag ←FPSCR.VE & (vxsnan_flag | vxvc_flag)
if vxsnan_flag=1 then SetFX(FPSCR.VXSNAN)
if vxvc_flag=1   then SetFX(FPSCR.VXVC)
if vex_flag=0 then do
    if bfp_COMPARE_GT(src1, src2)=1 then
        VSR[VRT+32] ← 0xFFFF_FFFF_FFFF_FFFF_FFFF_FFFF_FFFF_FFFF
    else
        VSR[VRT+32] ← 0x0000_0000_0000_0000_0000_0000_0000_0000
end

Programming Note

xscmpgtqp can be used to implement the C/C++ conditional operation, RESULT = (x>y) ? a : b. xscmpgtqp vGT,vX,vY xxsel vRESULT,vA,vB,vGT xscmpgtqp can also be used to implement the C/C++ conditional operation, RESULT = (x<y) ? a : b. xscmpgtqp vLT,vY,vX xxsel vRESULT,vA,vB,vLT