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not $s1,$t5     =     nor $s1, $t5, $0

The order of $t5 and $0 could be reversed. (You could also say $zero rather than $0.)

Implicit Immediate Operand

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

Sometimes the same mnemonic is used for a basic instruction and also for a pseudoinstruction. For example, you can use the mnemonic or for an or with register operands and also for an or with an immediate operand:

or $s0,$s1,0x00ff      translates into:      ori $s0,$s1,0x00ff

Here, the extended assembler notices the immediate operand and translates the instruction into an ori basic 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 or instruction.

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


Is there both a basic add instruction and an add immediate instruction?