Multiplication of signed integers
Coding numbers in computers

An n-bit x n-bit multiplication produces a 2n-bit result.

Instruction sets use different approaches:

• the IMUL instruction (IA-32 and Intel 64) multiplies n-bit numbers (n = 8,16,32) and provides the result on 2n bits (2n = 16, 32, 64);

• The M extension of the RISC-V instruction set has different instructions. MUL multiplies 2 32-bit numbers and places the 32 least significant bits of the result in a register. The MULH and MULHUS instructions multiply two 32-bit numbers (signed* signed and signed * unsigned) and place the 32 most significant bits of the result in a register.