xscvqpudz

VSX Scalar Convert with round to zero Quad-Precision to Unsigned Doubleword format X-form

xscvqpudz VRT,VRB

Converts a quad-precision floating-point value to an unsigned doubleword integer, rounding towards zero.

Encoding

Binary Layout

0:5

VRT

6:10

11:15

VRB

16:20

836

21:30

Format X-form

Opcode 0xFC110688

Extension VSX

Operands

VRT
Target Vector Register
VRB
Source Vector Register

Example

xscvqpudz v1, v3

Registers Altered

FPSCR.FPRF, FPSCR.FR, FPSCR.FI, FPSCR.XX, FPSCR.VXSNAN, FPSCR.VXCVI

Reference

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

Description

The instruction converts the quad-precision floating-point value in VSR[VRB+32] to an unsigned doubleword integer, rounding towards zero. The result is placed into doubleword element 0 of VSR[VRT+32]. Doubleword element 1 of VSR[VRT+32] is set to 0.

Operation

if MSR.VSX=0 then VSX_Unavailable()
reset_xflags()
src ←bfp_CONVERT_FROM_BFP128(VSR[VRB+32])
vxsnan_flag ←0
vxcvi_flag ←0
if src.class.QNaN=1 | src.class.SNaN=1 then do
    result ←0x0000_0000_0000_0000
    vxsnan_flag ←src.class.SNaN
    vxcvi_flag ←1
end else if src.class.Infinity=1 then do
    vxcvi_flag ←1
    if src.sign=0 then
        result ←0xFFFF_FFFF_FFFF_FFFF
    else
        result ←0x0000_0000_0000_0000
    end
end else if src.class.Zero then
    result ←0x0000_0000_0000_0000
else do
    rnd ←bfp_ROUND_TO_INTEGER(0b001,src)
    if bfp_COMPARE_GT(rnd, +264-1) then do
        result ←0xFFFF_FFFF_FFFF_FFFF
        vxcvi_flag ←1
    end else if bfp_COMPARE_LT(rnd, 0) then do
        result ←0x0000_0000_0000_0000
        vxcvi_flag ←1
    end else do
        result ←ui64_CONVERT_FROM_BFP(rnd)
        if xx_flag=1 then SetFX(FPSCR.XX)
    end
end
if vxsnan_flag=1 then SetFX(FPSCR.VXSNAN)
if vxcvi_flag=1  then SetFX(FPSCR.VXCVI)
vx_flag ←vxsnan_flag | vxcvi_flag
ex_flag ←FPSCR.VE & vx_flag
if ex_flag=0 then do
    VSR[VRT+32].dword[0] ←result
    VSR[VRT+32].dword[1] ←0x0000_0000_0000_0000
end
FPSCR.FR ←(vx_flag=0) & inc_flag
FPSCR.FI ←(vx_flag=0) & xx_flag

Programming Note

This instruction is used to convert a quad-precision floating-point number to an unsigned doubleword integer, rounding towards zero. Ensure the VSX facility is enabled; otherwise, it will raise an exception. Be cautious of NaNs and infinities, as they result in specific values and set condition flags. The operation does not require any particular alignment or privilege level.