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EE 333
Fall 2006
Computer Organization
Lecture 5
MIPS Instructions
Loops
Machine Instructions
Lillevik 333f06-l5
University of Portland
School of Engineering
1
EE 333
Fall 2006
Last time
• MIPS assembly language
• Arithmetic and logic instructions
• Load and store instructions
Lillevik 333f06-l5
University of Portland
School of Engineering
2
EE 333
Fall 2006
Write the program?
result  6  alpha  beta
Lillevik 333f06-l5
University of Portland
School of Engineering
3
EE 333
Fall 2006
Lets run the program
Lillevik 333f06-l5
University of Portland
School of Engineering
4
EE 333
Fall 2006
Instruction Classes
•
√ •
√ •
•
•
•
•
Arithmetic and logic (some more)
Load: li, la, lbu, lw
Store: sb, sw
Comparison
Branch and jump
Data Movement
Floating Point
Lillevik 333f06-l5
University of Portland
School of Engineering
5
EE 333
Fall 2006
Arithmetic and Logic
Instruction
Example
Meaning
And
and $s1, $s2, $s3
$s1 = $s2 & $s3
And immediate
andi $s1, $s2, 100
$s1 = $s2 & 100
Or
or $s1, $s2, $s3
$s1 = $s2 | $s3
Or immediate
ori $s1, $s2, 100
$s1 = $s2 | 100
Shift left logical
sll $s1, $s2, 10
$s1 = $s2 << 10
Shift right logical
srl $s1, $s2, 10
$s1 = $s2 >> 10
Only registers used for operands
Lillevik 333f06-l5
University of Portland
School of Engineering
6
EE 333
Fall 2006
Instruction Classes
√ • Arithmetic and logic: add, sub, and, or
√ • Load: li, la, lbu, lw
√ • Store: sb, sw
• Comparison
• Branch and jump
• Data Movement
• Floating Point
Lillevik 333f06-l5
University of Portland
School of Engineering
7
EE 333
Fall 2006
Branch and Jump
Instruction
Example
Meaning
Branch on equal
beq $s1, $s2, 100
If ($s1 = = $s2 ) go to
(PC +4 )+ 100
Branch on not equal
bne $s1, $s2, 100
If ($s1 ! = $s2 ) go to
(PC +4 )+ 100
Jump
j loop
Go to loop:
Jump and link
jal subroutine
$ra = PC + 4, go to
subroutine
Jump Register
jr $ra
PC = $ra
Lillevik 333f06-l5
University of Portland
School of Engineering
8
EE 333
Fall 2006
Loops in assembly
• Initialize loop counter
• Modify counter (decrement, increment)
• Check if counter = = end condition
– True, leave loop
– False, continue with loop
• Body of loop
• Continue with next pass in loop
Lillevik 333f06-l5
University of Portland
School of Engineering
9
EE 333
Fall 2006
Flowchart of loop
count = 5
count --
yes
count = = 0 ?
no
Body of loop
Lillevik 333f06-l5
University of Portland
Body could go ahead of test
School of Engineering
10
EE 333
Fall 2006
Loops
NOTE: you may place the
check after the body
How many times is
“body” executed?
(4 or 5?
Lillevik 333f06-l5
University of Portland
School of Engineering
11
EE 333
Fall 2006
Lets run the program
Lillevik 333f06-l5
University of Portland
School of Engineering
12
EE 333
Fall 2006
Write the program?
Write a loop that adds 4 to $t2, six times
Lillevik 333f06-l5
University of Portland
School of Engineering
13
EE 333
Fall 2006
Machine Instructions
• Definition: numeric (hex) versions of instruction
• Memory: contains binary number or machine
instruction, it’s what the hardware executes
• Formats
– R, register
– I, immediate
– J, jump
Lillevik 333f06-l5
University of Portland
NOTE: Result of
assembly is a machine
instruction
School of Engineering
14
EE 333
Fall 2006
Instruction Formats
Name
Fields
Size
6 bits
5 bits
5 bits
5 bits
5 bits
6 bits
R type
op
rs
rt
rd
shamt
funct
I type
op
rs
rt
J type
op
address/immediate
target address
32-bits
All instructions are 32-bits long
Lillevik 333f06-l5
University of Portland
School of Engineering
15
EE 333
Fall 2006
R-format
• Operation (op) code
All 0x00; exception mfc0 = 0x10,
• Funct determines specific instruction
add = 0x20, sub = 0x22, mult = 0x18, div = 0x1a
• Operands
Shamt = shift amount
– rd = destination register
– rs = first argument
– rt = second argument
Lillevik 333f06-l5
University of Portland
School of Engineering
16
EE 333
Fall 2006
R-format example
add $2, $3, $4
add rd, rs, rt
R type
Fields
Size
6 bits
5 bits
5 bits
5 bits
5 bits
6 bits
R type
op
rs
rt
rd
shamt
funct
00 0000
0 0011
0 0100
0 0010
0 0000
10 0000
0000 0000 0110 0100 0001 0000 0010 0000
0x 0064 1020
Lillevik 333f06-l5
University of Portland
School of Engineering
17
EE 333
Fall 2006
Find machine instruction?
sub $10, $6, $16
sub rd, rs, rt
R type
Fields
Size
6 bits
5 bits
5 bits
5 bits
5 bits
6 bits
R type
op
rs
rt
rd
shamt
funct
00 0000
0 0110
1 0000
0 1010
0 0000
10 0010
0x00d05022
Lillevik 333f06-l5
University of Portland
School of Engineering
18
EE 333
Fall 2006
I-format
• Op code examples
lw = 0x23, sw = 0x2b, beq = 0x04
• Operands
– rs = first argument
– rt = second argument
• Immediate = sign extended bits [15 – 0]
Lillevik 333f06-l5
University of Portland
School of Engineering
19
EE 333
Fall 2006
I-format example
lw $2, 100($3)
lw rt, adr (rs)
Name
Fields
Size
6 bits
5 bits
5 bits
16 bits
I type
op
rs
rt
address/immediate
10 0011
0 0011
0 0010
0000 0000 0110 0100
1000 1100 0110 0010 0000 0000 0110 0100
0x 8c62 0064
Lillevik 333f06-l5
University of Portland
School of Engineering
20
EE 333
Fall 2006
Find machine instruction?
sw
sw
$20, 64($8)
rt, adr (rs)
Name
Fields
Size
6 bits
5 bits
5 bits
16 bits
I type
op
rs
rt
address/immediate
101011
0 1000
1 0100
0000 0000 0100 0000
0xad14 0040
Lillevik 333f06-l5
University of Portland
School of Engineering
21
EE 333
Lillevik 333f06-l5
Fall 2006
University of Portland
School of Engineering
22
EE 333
Fall 2006
Write the program?
Write a loop that adds 4 to $t2, six times
Lillevik 333f06-l5
University of Portland
School of Engineering
23
EE 333
Fall 2006
Find machine instruction?
sub $10, $6, $16
sub rd, rs, rt
R type
Fields
Size
6 bits
5 bits
5 bits
5 bits
5 bits
6 bits
R type
op
rs
rt
rd
shamt
funct
00 0000
0 0110
1 0000
0 1010
0 0000
10 0010
0x 00d0 5022
Lillevik 333f06-l5
University of Portland
School of Engineering
24
EE 333
Fall 2006
Find machine instruction?
sw
sw
$20, 64($8)
rt, adr (rs)
Name
Fields
Size
6 bits
5 bits
5 bits
16 bits
I type
op
rs
rt
address/immediate
10 1011
0 1000
1 0100
0000 0000 0100 0000
0x ad14 0040
Lillevik 333f06-l5
University of Portland
School of Engineering
25