Implicit Immediate Operand

Some pseudoinstructions translate into different basic instructions depending on the type of operands used with it. A pseudoinstruction used with an immediate operand translates into different basic instructions than one used with all register operands.

Sometimes a mnemonic is used for a basic instruction and also for a pseudoinstruction. For example:

or $s0,$s1,0x00ff   ==  ori $s0,$s1,0x00ff

Here, the extended assembler notices the immediate operand and translates the instruction into an ori instruction. The resulting machine code is a 32-bit or immediate. However, the following is a basic instruction:

or $s0,$s1,$t1 

This assembly instruction is not changed. The resulting machine code is a 32-bit and instruction.

The mmenomic and is similar. It might call for the basic instruction and, or the basic instruction andi, or other basic instructions depending on the operands.