xsrqpxp

VSX Scalar Round Quad-Precision to Extended-Precision

xsrqpxp R, VRT, VRB, RMC

Rounds a quad-precision floating-point value to extended-precision.

Details

The xsrqpxp instruction rounds the quad-precision floating-point value in VSR[VRB+32] to extended-precision format and places the result into VSR[VRT+32]. The rounding mode is specified by RMC.

Pseudocode Operation

if MSR.VSX=0 then VSX_Unavailable()
reset_xflags()
if R=0 then
do
    if RMC=0b00 then rmode ←0b100
    if RMC=0b11 then do
        if FPSCR.RN=0b00 then rmode ←0b000
        if FPSCR.RN=0b01 then rmode ←0b001
        if FPSCR.RN=0b10 then rmode ←0b010
        if FPSCR.RN=0b11 then rmode ←0b011
    end
do
else do // R=1
    if RMC=0b00 then rmode ←0b000
    if RMC=0b01 then rmode ←0b001
    if RMC=0b10 then rmode ←0b010
    if RMC=0b11 then rmode ←0b011
end
do
src ← bfp_CONVERT_FROM_BFP128(VSR[VRB+32])
rnd ← bfp_ROUND_TO_BFP80(rmode, src)
result ← bfp128_CONVERT_FROM_BFP(rnd)
if vxsnan_flag=1 then SetFX(FPSCR.VXSNAN)
if ox_flag=1 then SetFX(FPSCR.OX)
if ux_flag=1 then SetFX(FPSCR.UX)
if xx_flag=1 then SetFX(FPSCR.XX)
vex_flag ← FPSCR.VE & vxsnan_flag
if vex_flag=0 then do
    VSR[VRT+32] ← result
    FPSCR.FPRF ← fprf_CLASS_BFP128(result)
end
do
FPSCR.FR ← (vxsnan_flag=0) & inc_flag
FPSCR.FI ← (vxsnan_flag=0) & xx_flag

Programming Note

The xsrqpxp instruction is used to round a quad-precision floating-point number to extended-precision format. Ensure that the VSX facility is enabled by checking MSR.VSX before using this instruction. The rounding mode is determined by the RMC field and can be overridden by the FPSCR.RN setting when R=0. Be aware of potential exceptions such as VXSNAN, OX, UX, and XX, which may set corresponding flags in the FPSCR register.

Example

xsrqpxp 0, v1, v3, 0

Encoding

Binary Layout

VRT

VRB

RMC

Format Z23-form

Opcode 0x7C000000

Extension VSX

Registers Altered FPSCR

Operands

R
Rounding Mode Control
VRT
Target Vector Register (upper half)
VRB
Source Vector Register (upper half)
RMC
Rounding Mode Control