FIT1008 Lecture Notes - Lecture 1: Call Stack, Instruction Register, Opcode
18 Jun 2018
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Department
Course
Professor
In#computer#architecture…
GPRs
•
Memory (from#bottom)
OS,#stack#segment,#heap,#static#data,#text#segment,#OS
○
•
CU#(Control#Unit)
Tells#ALU#and#registers#what#to#do,#based#on#opcode#and#operands#in#
IR
○
•
ALU#(Arithmetic#Logic#Unit)
Performs#computations#mainly#on#register#values,#not#main#memory
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Register-register#archi
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Integer#and#bitwise#arithmetic
○
•
Registers.(GPRs.-General.Purpose.Registers)
Prefixed#with#$,#32#in#total,#given#names#based#on#usage#conventions
Each#GPR#is#4B#in#size#(32#bits)#(1#word)
○
•
Fast#but#expensive
•
Physically#located#on#CPU#chip
•
$0
Zero
Constant#zero,#read-only,#no#change
$2,#$3
$v0,#$v1
Function#return#values#&#syscall#numbers
$4-$7
$a0-$a3
Function#and#syscall#arguments
$8-$15
$t0-$t7
Temporary#storage#(caller-saved)
$24,$25
$t8,#$t9
Temporary#storage#(caller-saved)
$16-$23
$s0-$s7
Temporary#storage#(callee-saved)
$29
$sp
Top-of-stack#pointer
$30
$fp
Stack#frame#pointer
$31
$ra
Function#return#address
Special#purpose#registers:
PC (Program#Counter)
Acts#as#bookmark,#telling#computer#where#it#has#stopped
§
Stores#memory#address#of#(i.e.#points#to)#next#instruction#to#be#
executed#in#the#text#segment
§
Instruction#address#increments#by#4(PC#=#PC#+#4)
§
○
HI, LO ("high",#"low")
Used#for#multiplication#and#division
§
Multiplying#2#32-bit#numbers#might#require#64#bits#to#fit
§
Integer#division#might#be#used
HI#contains#quotient,#LO#contains#remainder□
§
○
IR (Instruction#Register)
Stores#instruction#currently#being#executed#
§
○
MAR/MRR/MWR#(Memory#Address/Read/Write#Register)
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•
To#work#on#data,#we#load#data#into#a#register#to#work#on#it,#then#store#the#data#
back#into#memory#when#done.
Loading#from#memory#to#register:#lw (load#word)
Address#to#be#loaded#goes#to#MAR,#telling#memory#controller#to#read#it•
Data#at#address#goes#to#MRR,#which#is#copied#to#destination#GPR#specified#
instruction
•
Loading#from#register#to#memory:#sw (store#word)
Contents#of#GPR#specified#in#instruction#copied#to#MWR#and#written#to#
memory
•
Address#to#be#stored#goes#into#MAR#memory#controller#is#told#to#write•
Memory
For#memory#addresses#lower#than#text#segments Reserved#for#
OS
Executable#code#goes#here#(in#machine#code)
Starts#at#0x00400000#(4194304#in#dec)
OS#puts#code#here#("loading")#when#you#tell#it#to#run#a#program
Text#segment
Starts#at#0x10000000
Contains#program's:
Global#variables•
String#constants•
Static#data
Contains#programs'#dynamically#allocated#memory
Shrinks#when#memory#is#de-allocated,#either#by#garbage#collector#
or#programmer
Empty#at#start#of#program#execution
Grows.downwards as#more#memory#is#allocated#during#runtime
Heap#segment
Grows.upwards during#runtime
Starts#at#7FFFFFFC
Contains#system#stack:
Function#local#vars,#args,#return#addresses•
Saved#registers•
Frame#pointer•
Stack#segment
Week$1:$memory$+$registers
Wednesday,# 13#June#2018
14:29
Document Summary
Os, stack segment, heap, static data, text segment, os. Tells alu and registers what to do, based on opcode and operands in. Performs computations mainly on register values, not main memory. Prefixed with $, 32 in total, given names based on usage conventions. Each gpr is 4b in size (32 bits) (1 word) , function return values & syscall numbers. Acts as bookmark, telling computer where it has stopped. Stores memory address of (i. e. points to) next instruction to be executed in the text segment. Instruction address increments by 4(pc = pc + 4) Multiplying 2 32-bit numbers might require 64 bits to fit. To work on data, we load data into a register to work on it, then store the data back into memory when done. Loading from memory to register: lw (load word) Address to be loaded goes to mar, telling memory controller to read it.
