muladd rounding

Discussion created by sgratton on Apr 10, 2008
Latest reply on Apr 14, 2008 by michael.chu
Hi there,

Would anybody mind detailing the actual rounding procedure that the MULADD instruction follows in its various flavours, i.e. MULADD, MULADD_IEEE and MULADD_64? Do any of them actually work out a*b+c and then only round at the end?

(...I think I may have read somewhere that, for MULADD at least, a*b is truncated and then this truncated product is added with rounding to c, but it'd be good to know for sure and if this applies to all variants).