Error in v64i32 type in x86 backend

Thank you;
i have changed as it fine now?

def VADD_256B : I<0xFE, MRMDestReg, (outs VR2048:$dst), (ins VR2048:$src1, VR2048:$src2),
“VADD_256B\t{$src, $dst|$dst, $src}”, [(set VR2048:$dst, (add VR2048:$src1, VR2048:$src2))]]>;

Also here i have changed class RI to I. Does it make any difference?

You don’t want RI. That’s used for instructions that need a reg prefix. You need to use $src1 and $src2 in the assembly string too. It also looks like you have two closing ] brackets.

Oops that should have said “REX prefix” in the first sentence.