Receiving LLV Error in Custom Backend


I am receiving an LLVM Error from a custom 16-bit backend I am creating. I am having trouble understanding the error/problem and how to go about solving it. The error is:

LLVM ERROR: Cannot select: t29: i32,ch = load<LD2[%x.addr], anyext from i16> t14, FrameIndex:i16<0>, undef:i16
t7: i16 = FrameIndex<0>
t9: i16 = undef
In function: mul_add

Can anyone provide any pointers as to what the problem is and potential places I should look to fix it?

Thanks and best regards,