What does the following assembly language instruction do?
addu $t5,$zero,$t7
It
copies
the contents of register
$t7
into register
$t5.
The
addu instruction,
used as above with register $zero, copies a bit pattern from the source register into
the destination register.
This is usually called a
move operation, although the source register does not change.
It is often convenient to move a value from one
register to another.
It
is awkward to say "add" when you mean "move".
The extended assembler
allows you to use the mnemonic
move
instead of addu.
This mnemonic does not correspond to a new machine
instruction.
It is just a way of asking for the same instruction
by using a more intuitive mnemonic.
It is a pseudoinstruction that the assembler
translates into
the appropriate basic assembly instruction.
A pseudoinstruction is an instruction that the extended assembler replaces with one or more basic assembly instructions.
The
extended assembler implements
many pseudoinstructions.
Sometimes they are just convenient re-naming of basic assembly
instructions.
Other times they correspond to a small, convenient
sequence of basic assembly instructions.
Here is the move pseudoinstruction:
move d,s # copy the contents of
# the source register s
# to the destination
# register d
# (pseudoinstruction)
The registers d and s can be
specified by using register mnemonic names
(such as $t5 or $zero) or by
using register numbers
(such as $13 or $0).
This is true for all instructions of the extended assembler.
Write the instruction that moves (copies) the contents of
register $t3 into register $s1.
,