 Solution

More processor registers can reduce register spills and the associated loads and stores. A richer instruction set may also replace several old machine instructions by one new operation. Both effects can decrease the number of instructions in a compiled program, although a particular program might obtain no benefit.

Wider instruction encodings increase the bytes per instruction. Consequently the total machine-code size can increase or decrease: approximately, it is instruction count times average encoded instruction width, with alignment and padding also relevant. There is no universal net direction without the program and revised encoding. The length of assembly language source text is a separate matter and is not determined by instruction bit widths.