The followoing opcodes are defined in VEX/pub/libvex_ir.h and used in
the various VEX/priv/host* and VEX/priv/guest* files - but are not
implemented in coregrind/m_translate.c.  I don't know why that is,
but I speculate they never occure in actual code.  markro 2/24/2015

Iop_ExpCmpNE8
Iop_F16toF32x4
Iop_F32toF16x4
Iop_MulHi32Sx4
Iop_MulHi32Ux4
Iop_PwMax32Fx4
Iop_PwMin32Fx4
Iop_RSqrtEst32Ux2
