CS 230 – Introduction to Computers and Computer Systems Lecture 7 – Assembly Language Intro CS 230 - Spring 2020 2-1
System Layers Python/C/Racket Code Multiprocessing and Operating Systems Build and Runtime Environments Memory and Caching CS 230 CPU Instructions Here now! and Pipelining Binary Signals & Number Representation Finished! Logic Gates Transistors and Electrical Properties CS 230 - Spring 2020 2-2
Machine Code Binary code – comprised of 0s and 1s “Direct” execution by processor Program composed of instructions operation code (opcode) + operands instructions control processor opcode says what thing to do operands say what to apply that thing to CS 230 - Spring 2020 2-3
Assembly Language Human- readable “programming language” very simple compared to Racket, Python, etc. Almost direct mapping to machine code except a few concepts we’ll cover later Assembler turns it into machine code process is called “assembling” rather than “compiling” CS 230 - Spring 2020 2-4
Instruction Set Repertoire of instructions of a processor Different processors have different sets many commonalities mathematical memory access control flow CS 230 - Spring 2020 2-5
MIPS Architecture MIPS: Microprocessor without Interlocked Pipeline Stages details later Multiple revisions, systems, and compilers not just a single standard MIPS we use simplified version in CS 230 CS 230 - Spring 2020 2-6
MIPS Assembly Language Each instruction takes 32 bits 4 bytes = 1 word Arithmetic instructions operate on registers 32 registers available numbered $0 to $31 refer to them in assembly language with $[register number] register $0 always equals 0 Instructions have up to 3 operands 1 st is destination, 2 nd and 3 rd are sources same register can be source and destination CS 230 - Spring 2020 2-7
Immediate Addition addi $t, $s, i add register s and value i value i can be negative value i can be hexadecimal place result in register t example: addi $1, $2, 14 sets content of $1 to the content of $2 plus 14 10 often used to initialize registers: addi $t, $0, i CS 230 - Spring 2020 2-8
Addition and Subtraction add $d, $s, $t add content of register s and t place result in register d example: add $3, $2, $1 sets content of $3 to content of $2 plus content of $1 sub $d, $s, $t subtract register t from s place result in register d example: sub $6, $5, $4 sets content of $6 to content of $5 minus content of $4 CS 230 - Spring 2020 2-9
Example addi $2, $0, -3 add $3, $2, $0 sub $3, $3, $2 jr $31 What is the value in register $3 at the end of this program? CS 230 - Spring 2020 2-10
Example addi $2, $0, -3 add $3, $2, $0 $0 $1 $2 $3 $4 $5 … ? … sub $3, $3, $2 0 ? ? ? ? jr $31 What is the value in register $3 at the end of this program? CS 230 - Spring 2020 2-11
Example addi $2, $0, -3 add $3, $2, $0 $0 $1 $2 $3 $4 $5 … ? … sub $3, $3, $2 0 ? -3 ? ? jr $31 What is the value in register $3 at the end of this program? CS 230 - Spring 2020 2-12
Example addi $2, $0, -3 add $3, $2, $0 $0 $1 $2 $3 $4 $5 … ? … sub $3, $3, $2 0 ? -3 -3 ? jr $31 What is the value in register $3 at the end of this program? CS 230 - Spring 2020 2-13
Example addi $2, $0, -3 add $3, $2, $0 $0 $1 $2 $3 $4 $5 … ? … sub $3, $3, $2 0 ? -3 0 ? jr $31 What is the value in register $3 at the end of this program? CS 230 - Spring 2020 2-14
Example addi $2, $0, -3 add $3, $2, $0 $0 $1 $2 $3 $4 $5 … ? … sub $3, $3, $2 0 ? -3 0 ? jr $31 What is the value in register $3 at the end of this program? • $3 = 0 10 CS 230 - Spring 2020 2-15
Try it yourself addi $1, $0, 13 addi $2, $1, 0xA sub $4, $2, $1 jr $31 What is the value in register $4 at the end of this program? CS 230 - Spring 2020 2-16
Try it yourself addi $1, $0, 13 addi $2, $1, 0xA $0 $1 $2 $3 $4 $5 … ? … sub $4, $2, $1 0 ? ? ? ? jr $31 What is the value in register $4 at the end of this program? CS 230 - Spring 2020 2-17
Try it yourself addi $1, $0, 13 addi $2, $1, 0xA $0 $1 $2 $3 $4 $5 … ? … sub $4, $2, $1 0 13 ? ? ? jr $31 What is the value in register $4 at the end of this program? CS 230 - Spring 2020 2-18
Try it yourself addi $1, $0, 13 addi $2, $1, 0xA $0 $1 $2 $3 $4 $5 … ? … sub $4, $2, $1 0 13 23 ? ? jr $31 What is the value in register $4 at the end of this program? CS 230 - Spring 2020 2-19
Try it yourself addi $1, $0, 13 addi $2, $1, 0xA $0 $1 $2 $3 $4 $5 … 0 13 23 ? 10 ? … sub $4, $2, $1 jr $31 What is the value in register $4 at the end of this program? CS 230 - Spring 2020 2-20
Try it yourself addi $1, $0, 13 addi $2, $1, 0xA $0 $1 $2 $3 $4 $5 … 0 13 23 ? 10 ? … sub $4, $2, $1 jr $31 What is the value in register $4 at the end of this program? • $4 = 10 10 CS 230 - Spring 2020 2-21
Example Consider the equation z = x + y + 83 10 Assume x represents $1, y represents $2, and z represents $3. Write a MIPS assembly language program that evaluates the value of z given x and y . CS 230 - Spring 2020 2-22
Example Consider the equation z = x + y + 83 10 Assume x represents $1, y represents $2, and z represents $3. Write a MIPS assembly language program that evaluates the value of z given x and y . add $3, $1, $2 CS 230 - Spring 2020 2-23
Example Consider the equation z = x + y + 83 10 Assume x represents $1, y represents $2, and z represents $3. Write a MIPS assembly language program that evaluates the value of z given x and y . add $3, $1, $2 addi $3, $3, 83 CS 230 - Spring 2020 2-24
Example Consider the equation z = x + y + 83 10 Assume x represents $1, y represents $2, and z represents $3. Write a MIPS assembly language program that evaluates the value of z given x and y . add $3, $1, $2 addi $3, $3, 83 jr $31 CS 230 - Spring 2020 2-25
Try it Yourself Consider the equation z = (x – y) – (0xB3C + y) Assume x represents $1, y represents $2, and z represents $3. Write a MIPS assembly language program that evaluates the value of z given x and y . CS 230 - Spring 2020 2-26
Try it Yourself Consider the equation z = (x – y) – (0xB3C + y) Assume x represents $1, y represents $2, and z represents $3. Write a MIPS assembly language program that evaluates the value of z given x and y . sub $4, $1, $2 CS 230 - Spring 2020 2-27
Try it Yourself Consider the equation z = (x – y) – (0xB3C + y) Assume x represents $1, y represents $2, and z represents $3. Write a MIPS assembly language program that evaluates the value of z given x and y . sub $4, $1, $2 addi $3, $2, 0xB3C CS 230 - Spring 2020 2-28
Try it Yourself Consider the equation z = (x – y) – (0xB3C + y) Assume x represents $1, y represents $2, and z represents $3. Write a MIPS assembly language program that evaluates the value of z given x and y . sub $4, $1, $2 addi $3, $2, 0xB3C sub $3, $4, $3 CS 230 - Spring 2020 2-29
Try it Yourself Consider the equation z = (x – y) – (0xB3C + y) Assume x represents $1, y represents $2, and z represents $3. Write a MIPS assembly language program that evaluates the value of z given x and y . sub $4, $1, $2 addi $3, $2, 0xB3C sub $3, $4, $3 jr $31 CS 230 - Spring 2020 2-30
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