Transcript The Instruction Set Architecture

The Instruction Set
Architecture
September 27th, 2007
By: Corbin Johnson
CS 146
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What is the Instruction Set
Architecture?

It contains instructions to use and manipulate
programmer-accessible hardware in a computer.
in terms of
place in a
computer
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What is the relationship between
the Instruction Set Architecture and
Assembly / Machine language?

An assembly / machine program is made
up of the instructions in the ISA and makes
use of registries in the ISA.
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Here’s how it works
Higher level languages (Java, C++, etc…)
are translated into assembly / machine
language by compilers.
 When a user calls the program, the
compiled program is loaded into RAM.
 The program then executes, line by line,
until the Operating System takes back
control of the computer.

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A Sample Computer: ARC
The ARC has an ISA that is a subset of the
ISA of the SPARC, or Scalable Processor
Architecture processor developed by Sun
in the mid 80’s.
 Has most important features of SPARC
but has left out most complex portions.
 ARC is considered a RISC or “Reduced
Instruction Set Computer.”

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Goal: Program the ARC

A program can be written for the ARC
using the ISA of the ARC.

Discuss three main parts of ARC:
RAM
 Processor (CPU)
 Instruction Set

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
Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
32 bit memory
 Byte Addressable
 Memory-mapped I/O

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

Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
The OS
211 bits of memory
 Only OS uses this
area

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

Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
The User Space
Undefined amount
 User’s program fills
Into unused space
 Designed to work well
If stack small and
Program large or
Vice versa.

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

Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
The System Stack
Undefined amount
 Program’s execution
Uses stack for storage
 Grows towards lower
Memory as user’s
Space grows towards
Higher memory.

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

Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
Memory-Mapped I/O
Static slots
 Data talks with input
And output devices

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

Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
The CPU
Executes programs
In main memory
 Contains Registries
Holding data
 Four-Step cycle to
Execute program

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

Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
The Four Step
Cycle
1)
2)
3)
4)
Fetch next instruction
Decode the instruction
Read operand in main
memory if any
Execute instruction
and store results, if
any.
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

Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
The registers


Positions in CPU that
hold data during
calculation
Special Registries:
%r0, %sp, %link,
%psr, % pc
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

Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
The Arithmetic and
Logic Unit


Takes care of
calculations that need
to be executed
Fed instructions by
the Control Unit
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

Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
Some Features of the ISA:



All of the instructions in the Instruction Set
are 32 bit
ARC is load-store: all operands must be
either loaded to use or stored in memory to
be stored
ARC is two’s compliment
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

Discuss three main parts of ARC:
 RAM
 Processor (CPU)
 Instruction Set
Three different classes of instructions:



Arithmetic and Logic
Memory Access
Transfer of Control
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

Three different classes of instructions:

Arithmetic and Logic

Memory Access

Transfer of Control
Arithmetic and Logic
Includes instructions
like Add and Subtract
Also includes
instructions like AND,
OR and NOT.
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

Three different classes of instructions:

Arithmetic and Logic

Memory Access

Transfer of Control
Memory Access
Includes instructions
load and store
Loads into registers
and stores into
memory slots in RAM
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

Three different classes of instructions:

Arithmetic and Logic

Memory Access

Transfer of Control
Transfer of Control
Instructions help get
to different places in
program
Place in ISA where
conditionals first are
seen (if statement,
loops, etc…)
Essentially changes
program counter
register
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The Syntax of the ARC Assembly
Language

The Mnemonic is a way for the programmer
to remember the instruction’s name.

A Compiler will take a written assembly
language code and convert it to machine
code.
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What’s that cc after addcc?

CC stands for Condition Code and they are set in the
PSR (it is a 32 bit registry)

There are 4:

Z: if the result of the instruction is zero, this flag is set.

N: if the most significant bit is 1, this bit is set

C: if there is a carry out of the MSB or a borrow into it,
this flag is set.

V: Overflow. The result cannot be represented in 32
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bits.
THE PSR
(Processor Status Register)
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More on The Syntax of the ARC
Assembly Language

Brackets [ ] around an operand means to load
(or store) from (or in) the memory which is
addressed by the operand within the brackets.
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A few of the 35 instructions
The ARC ISA has more than 35
instructions.
 Memory: ld [%r5 + 2064] , %r1
 Arithmetic: addcc %r1, 129, %r1
 Control: call sub_r

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From Assembly Language to
Machine Code

Each Assembly
Language
instruction is
translated one
line for one line
(one to one).
rd: destination registry
Cond: based on the PSR, this
executes differently
Simm13: a user defined
constant in 2’s compliment
in 13 bits.
Rs1: registry 1 in the CPU
Disp30/Disp 22: 30/22 bit number is
shifted to the left to achieve 32 bit
destination of it’s function.
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Summary
Although not explicitly shown, this method
will take an upper level program and
convert it into actual things the computer
can do.
 Involves translation from the higher level
into assembly language into machine code
using the ARC ISA.

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