Question

1. MIPS ISA does not have all the instruction that one would wish for, for a good reason, the main “customer” is not a human programmer but a compiler. Pseudo-instructions can be added to an ISA to simplify the programming by humans. These are essentially mnemonics for a sequence of ISA instructions. Provide the expansions for the following pseudo-instructions:

Name	Assembly	C operation	Expansion
nop	nop	{}
not	not $r1, $r2	$r1 = ~$r2
branch if greater than	bgt $r1, $r2, C	if (x > y) then
move	mov $r1, $r2	x = y
clear	clear $r1	x = 0
load 16-bit immediate without sign extension	li $r1, C	x = C

Answer 1

Expansions for pseudo code instructions as follows:

1. sll $zero, $zero, 0
2. not $t, $s, $zero
3. slt $at, $t, $sbne $at, $zero, C
4. $t, $s, $zero
5. $t, $zero, $zero
6. $t, $zero, C_lo