Pseudoinstructions: logical

Instruction

Real instructions

Semantics

not $rd, $rs

addi    $at, $0, -1

# R[1] = -1

xor     $rd, $rs, $at

# R[d] = R[s] ^ R[1]

Better way:

not $rd, $rs

nor $rd, $rs, $0

# R[d] = ~R[s]

Why does this work?