natawut nupairojassembly language1 introduction to assembly programming

Natawut Nupairoj Assembly Language 1

Introduction to Assembly Programming


Outline

• What is assembly ?• How does it look like ?• Type of instructions.• Assembler and other tools.


What is Assembly ?

• Symbolic representation of machine language.– opcodes– operands– labels

• More readable to human (not computer).

add A, B 1000111000010110

• Easy to translate to machine language.


Level of Languages

swap(int v[], int k)

{ int temp;

temp = v[k];

v[k] = v[k+1];

v[k+1] = temp;

}

swap:

muli $2, $5, 4

add $2, $4, $2

lw $15, 0($2)

...

000010001101101100110000

000010001101101100110000

000010001101101100110000

000010001101101100110000

...

C Compiler

Assembler

•High level: C / Java / Pascal•Low level: Assembly / Bytecode•Machine Language


When to Use Assembly

• When speed and size matter !– Equipment that must response very quickly.– Embedded devices.– Device driver.– When the resource is limited.

• When we use the specialized instructions:– 3D graphic library

• When there is no compiler !


When to Use Assembly

• When you want to understand internal architecture of a CPU !– Complex Instruction Set Computers (CISC)

• Intel x86, Intel Pentium, etc.

– Reduce Instruction Set Computers (RISC)• DEC Alpha, Sun SPARC, HP P/A, MIPS, Pentium II/III/4,

etc.

– Very-Large Instruction Word (VLIW)• Intel Itanium (Pentium 4), Transmeta Crusoe.

– Pentium II/III/4 are special cases• Outside CICS, inside RISC.


Drawbacks of Assembly

• Machine-dependent:– must be rewritten on another computer architecture.– not portable.

• Longer codes to write.• Difficult to read and understand.


Inside Computer

MEMORY

CPU

ALU

R egister

I nput

O utput


Instruction Formats

• Different CPUs, different formats.• Something in common:

– opcode: instruction• What is the command ?• Arithmetic• Branch

– operand: perform that command on ?• What is the data ?• registers• memory• constant


Example: adding two numbers

• Sparc: r2 = r0 + r1add %r0, %r1, %r2

• MIPS: s2 = s0 + s1add $s2, $s0, $s1

• IBM 370: R1 = R1 + R2AR R1, R2


Instruction Formats (Cont’)

• Limited number of operands per instruction:

r5 = r1 + 8 - r2 + r3

add %r1, 8, %r1 ! r1 = r1 + 8sub %r1, %r2, %r1 ! r1 = r1 - r2add %r1, %r3, %r5 ! r5 = r1 + r3


Translation Process

• Assembler:– translate assembly to a binary code.– check syntax.– produce an object file (not executable).

• Linker:– combine one or more object files.– resolve references to other object files / libraries.– produce an executable program.


Translation Process (Cont’)

Assembly Program

Assembler

ObjectFile

ObjectFile

ObjectFile

Libraries

Linker

Executable File


Other Tools

• Debugger:– trace assembly program.– run a program in a step-by-step fashion.– can display values of memory and registers.

• Profiler:– estimate time that a program spends in each

subroutine.– find the one with the longest time, optimize it.

natawut nupairojassembly language1 introduction to assembly programming

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