xvnmaddasp

Vector Negative Multiply-Add Single-Precision Type-A

xvnmaddasp XT,XA,XB

Performs a negative multiply-add operation on single-precision floating-point elements.

Details

The xvnmaddasp instruction multiplies the single-precision floating-point value in VSR[XA] by the single-precision floating-point value in VSR[XT], adds the result to the single-precision floating-point value in VSR[XB], and stores the result back into VSR[XT].

Pseudocode Operation

if MSR.VSX=0 then VSX_Unavailable()
ex_flag ←0b0
do i = 0 to 3
    reset_xflags()
    src1 ←bfp_CONVERT_FROM_BFP32(VSR[32×AX+A].word[i])
    src2 ←bfp_CONVERT_FROM_BFP32(VSR[32×TX+T].word[i])
    src3 ←bfp_CONVERT_FROM_BFP32(VSR[32×BX+B].word[i])
    v   ←bfp_MULTIPLY_ADD(src1,src3,src2)
    rnd ←bfp_NEGATE(bfp_ROUND_TO_BFP32(FPSCR.RN,v))
    vresult.word[i] ←bfp32_CONVERT_FROM_BFP(rnd)
    if vxsnan_flag=1 then SetFX(FPSCR.VXSNAN)
    if vximz_flag=1 then SetFX(FPSCR.VXIMZ)
    if vxisi_flag=1 then SetFX(FPSCR.VXISI)
    if ox_flag=1 then SetFX(FPSCR.OX)
    if ux_flag=1 then SetFX(FPSCR.UX)
    if xx_flag=1 then SetFX(FPSCR.XX)
    ex_flag ←ex_flag | (FPSCR.VE & vxsnan_flag) | (FPSCR.VE & vximz_flag) | (FPSCR.VE & vxisi_flag) | (FPSCR.OE & ox_flag) | (FPSCR.UE & ux_flag) | (FPSCR.XE & xx_flag)
end
if ex_flag=0 then VSR[32×TX+T] ←vresult

Programming Note

This instruction is commonly used in vectorized floating-point computations where negative multiplication and addition are required. Ensure that the VSX (Vector Scalar Extensions) are enabled by checking MSR.VSX before using this instruction. Be aware of potential exceptions such as NaNs, infinities, or underflows, which can set flags in FPSCR and may trigger exceptions based on the current settings.

Example

xvnmaddasp vs1, vs2, vs3

Encoding

Binary Layout

1544

Format XX3-form

Opcode 0xF0000608

Extension VSX

Registers Altered FPSCR, VXSNAN, VXIMZ, Vxisi, OX, UX, XX

Operands

XT
Target Vector Register
XA
Source Vector Register
XB
Source Vector Register