This document contains lecture slides on machine-level programming basics from a computer systems course at Carnegie Mellon University. It begins with an overview of the history of Intel processors and architectures. It then discusses C, assembly, and machine code, and covers basic assembly concepts like registers, operands, and moving data. The slides provide examples of arithmetic and logical operations in assembly. It also includes details on Intel x86 processors and their evolution over time.
HIS 2017 Mark Batty-Industrial concurrency specification for C/C++jamieayre
Modern computer systems have intricate memory hierarchies that violate the intuition of a global timeline of interleaved memory accesses. In these so-called relaxed-memory systems, it can be dangerous to use intuition, specifications are universally unreliable, and the outcome of testing is both wildly nondeterministic and dependent on hardware that is getting more permissive of odd behaviour with each generation. These complications pervade the whole system, and have led to bugs in language specifications, deployed processors, compilers, and vendor-endorsed programming idioms – it is clear that current engineering practice is severely lacking.
I will describe my part of a sustained effort in the academic community to tackle these problems by applying a range of techniques, from exhaustive testing to mechanised formal specification and proof. I will focus on a vein of work with strong industrial impact: the formalisation, refinement and validation of the 2011/14/17 C and C++ concurrency design, leading to changes in the ratified international standard, and ultimately uncovering fundamental flaws that lead us to the state of the art in concurrent language specification. This work represents an essential enabling step for verification on modern concurrent systems
HIS 2017 Mark Batty-Industrial concurrency specification for C/C++jamieayre
Modern computer systems have intricate memory hierarchies that violate the intuition of a global timeline of interleaved memory accesses. In these so-called relaxed-memory systems, it can be dangerous to use intuition, specifications are universally unreliable, and the outcome of testing is both wildly nondeterministic and dependent on hardware that is getting more permissive of odd behaviour with each generation. These complications pervade the whole system, and have led to bugs in language specifications, deployed processors, compilers, and vendor-endorsed programming idioms – it is clear that current engineering practice is severely lacking.
I will describe my part of a sustained effort in the academic community to tackle these problems by applying a range of techniques, from exhaustive testing to mechanised formal specification and proof. I will focus on a vein of work with strong industrial impact: the formalisation, refinement and validation of the 2011/14/17 C and C++ concurrency design, leading to changes in the ratified international standard, and ultimately uncovering fundamental flaws that lead us to the state of the art in concurrent language specification. This work represents an essential enabling step for verification on modern concurrent systems
How to Select Hardware for Internet of Things Systems?Hannes Tschofenig
With the increasing commercial interest in Internet of Things (IoT) the question about a reasonable hardware configuration surfaces again and again.
Peter Aldworth, a hardware engineer with more than 19 years of experience, discusses this topic in a presentation given to the IETF community.
Concisely describe the following terms 40 1. Source code 2. Object c.pdffeelinggift
Concisely describe the following terms 40% 1. Source code 2. Object code 3. Compiler 4.
Algorithm 5. Byte (used for what purpose) 6. Nano second or ns (used for what purpose) 7.
System program (provide two examples) 8. Application program (provide two examples) 9.
Preprocessing directive 10. ASCII
Solution
Answers:
1.
A programmer writes a program in a particular programming language (ex : c , c++ ,java).This
form of the program is called the source code. it can be read and easily understood by a human
being.
For example : Source code for Hello world program is:
#include
void main()
{
printf(“Hello World”);
}
2.
An interpreter or a complier translates source code into executable machine code. This machine
code is called as the object code.
Complier translates source code into object code. Object code contains instructions to be
executed by the computer.
3.
A complier is a program that translates a source program or source code written in particular
programming language ( such as c , c++ or java ) into machine language (code).
Example : Turbo c compiler.
4.
Step –by- step instructions of a program is called is an algorithm.
5.
1 byte = 8 bits.
A byte is a unit of measurement used to measure the data.
Each byte represents a character.
6.
A nano second or ns is a unit of time representing 10-9 or 1 billionth of a second. computer
memory speed is represented in nano seconds.
7.
It is a type of computer program that is designed to run a computer’s hardware and application
programs.
Examples are :
OS (operating system)
BIOS
Boot program.
8.
Application program is a software program that runs on computer.
Examples are word processors, web browsers.
9.
Preprocessor directives are invoked by the complier to process some programs before
compilation.
Preprocessor directives are lines included in a program that begin with the character #.
10.
ASCII: American Standard Code for Information Interchange)
It is the most common format for text files in computers and on the internet.
Short Answers:
1.
Source code
|
Complier
| Assembly code
Assembler
Libraries | Object code
Link Editor
|
Executable code
2.
a)
Memory unit (storage)
ALU (Arithmetic and Logical unit)
CU (Control Unit)
b)
Storage:
All the data to be processed and the instruction required for processing.
Intermediate results of processing.
Final results of processing before these results are released to an output device.
ALU (Arithmetic and Logical unit):
It performs all the arithmetic operations (like addition, subtraction etc) and logical operations.
CU (Control Unit):
The control unit directs and controls the activities of the internal and external devices.
3.
Fetch the instruction
Decode the instruction
Read the effective address
Execute the instruction
In executing the instruction Arithmetic and Logical unit (ALU) performs mathematical or logical
operations .ALU sends a condition signal back to the control unit (CU). The result generated by
the operation is stored in the main memory or sent to o.
Computer Architecture – An IntroductionDilum Bandara
Overview on high-level design of internal components of a computer. Cover step-by-step execution of a program through ALU while accessing & updating registers
Search and Society: Reimagining Information Access for Radical FuturesBhaskar Mitra
The field of Information retrieval (IR) is currently undergoing a transformative shift, at least partly due to the emerging applications of generative AI to information access. In this talk, we will deliberate on the sociotechnical implications of generative AI for information access. We will argue that there is both a critical necessity and an exciting opportunity for the IR community to re-center our research agendas on societal needs while dismantling the artificial separation between the work on fairness, accountability, transparency, and ethics in IR and the rest of IR research. Instead of adopting a reactionary strategy of trying to mitigate potential social harms from emerging technologies, the community should aim to proactively set the research agenda for the kinds of systems we should build inspired by diverse explicitly stated sociotechnical imaginaries. The sociotechnical imaginaries that underpin the design and development of information access technologies needs to be explicitly articulated, and we need to develop theories of change in context of these diverse perspectives. Our guiding future imaginaries must be informed by other academic fields, such as democratic theory and critical theory, and should be co-developed with social science scholars, legal scholars, civil rights and social justice activists, and artists, among others.
How to Select Hardware for Internet of Things Systems?Hannes Tschofenig
With the increasing commercial interest in Internet of Things (IoT) the question about a reasonable hardware configuration surfaces again and again.
Peter Aldworth, a hardware engineer with more than 19 years of experience, discusses this topic in a presentation given to the IETF community.
Concisely describe the following terms 40 1. Source code 2. Object c.pdffeelinggift
Concisely describe the following terms 40% 1. Source code 2. Object code 3. Compiler 4.
Algorithm 5. Byte (used for what purpose) 6. Nano second or ns (used for what purpose) 7.
System program (provide two examples) 8. Application program (provide two examples) 9.
Preprocessing directive 10. ASCII
Solution
Answers:
1.
A programmer writes a program in a particular programming language (ex : c , c++ ,java).This
form of the program is called the source code. it can be read and easily understood by a human
being.
For example : Source code for Hello world program is:
#include
void main()
{
printf(“Hello World”);
}
2.
An interpreter or a complier translates source code into executable machine code. This machine
code is called as the object code.
Complier translates source code into object code. Object code contains instructions to be
executed by the computer.
3.
A complier is a program that translates a source program or source code written in particular
programming language ( such as c , c++ or java ) into machine language (code).
Example : Turbo c compiler.
4.
Step –by- step instructions of a program is called is an algorithm.
5.
1 byte = 8 bits.
A byte is a unit of measurement used to measure the data.
Each byte represents a character.
6.
A nano second or ns is a unit of time representing 10-9 or 1 billionth of a second. computer
memory speed is represented in nano seconds.
7.
It is a type of computer program that is designed to run a computer’s hardware and application
programs.
Examples are :
OS (operating system)
BIOS
Boot program.
8.
Application program is a software program that runs on computer.
Examples are word processors, web browsers.
9.
Preprocessor directives are invoked by the complier to process some programs before
compilation.
Preprocessor directives are lines included in a program that begin with the character #.
10.
ASCII: American Standard Code for Information Interchange)
It is the most common format for text files in computers and on the internet.
Short Answers:
1.
Source code
|
Complier
| Assembly code
Assembler
Libraries | Object code
Link Editor
|
Executable code
2.
a)
Memory unit (storage)
ALU (Arithmetic and Logical unit)
CU (Control Unit)
b)
Storage:
All the data to be processed and the instruction required for processing.
Intermediate results of processing.
Final results of processing before these results are released to an output device.
ALU (Arithmetic and Logical unit):
It performs all the arithmetic operations (like addition, subtraction etc) and logical operations.
CU (Control Unit):
The control unit directs and controls the activities of the internal and external devices.
3.
Fetch the instruction
Decode the instruction
Read the effective address
Execute the instruction
In executing the instruction Arithmetic and Logical unit (ALU) performs mathematical or logical
operations .ALU sends a condition signal back to the control unit (CU). The result generated by
the operation is stored in the main memory or sent to o.
Computer Architecture – An IntroductionDilum Bandara
Overview on high-level design of internal components of a computer. Cover step-by-step execution of a program through ALU while accessing & updating registers
Search and Society: Reimagining Information Access for Radical FuturesBhaskar Mitra
The field of Information retrieval (IR) is currently undergoing a transformative shift, at least partly due to the emerging applications of generative AI to information access. In this talk, we will deliberate on the sociotechnical implications of generative AI for information access. We will argue that there is both a critical necessity and an exciting opportunity for the IR community to re-center our research agendas on societal needs while dismantling the artificial separation between the work on fairness, accountability, transparency, and ethics in IR and the rest of IR research. Instead of adopting a reactionary strategy of trying to mitigate potential social harms from emerging technologies, the community should aim to proactively set the research agenda for the kinds of systems we should build inspired by diverse explicitly stated sociotechnical imaginaries. The sociotechnical imaginaries that underpin the design and development of information access technologies needs to be explicitly articulated, and we need to develop theories of change in context of these diverse perspectives. Our guiding future imaginaries must be informed by other academic fields, such as democratic theory and critical theory, and should be co-developed with social science scholars, legal scholars, civil rights and social justice activists, and artists, among others.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
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Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
91mobiles recently conducted a Smart TV Buyer Insights Survey in which we asked over 3,000 respondents about the TV they own, aspects they look at on a new TV, and their TV buying preferences.
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
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Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
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LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
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1. Carnegie Mellon
1
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Machine-Level Programming I: Basics
15-213/18-213: Introduction to Computer Systems
5th Lecture, Sep. 15, 2015
Instructors:
Randal E. Bryant and David R. O’Hallaron
2. Carnegie Mellon
2
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Today: Machine Programming I: Basics
History of Intel processors and architectures
C, assembly, machine code
Assembly Basics: Registers, operands, move
Arithmetic & logical operations
3. Carnegie Mellon
3
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Intel x86 Processors
Dominate laptop/desktop/server market
Evolutionary design
Backwards compatible up until 8086, introduced in 1978
Added more features as time goes on
Complex instruction set computer (CISC)
Many different instructions with many different formats
But, only small subset encountered with Linux programs
Hard to match performance of Reduced Instruction Set Computers
(RISC)
But, Intel has done just that!
In terms of speed. Less so for low power.
4. Carnegie Mellon
4
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Intel x86 Evolution: Milestones
Name Date Transistors MHz
8086 1978 29K 5-10
First 16-bit Intel processor. Basis for IBM PC & DOS
1MB address space
386 1985 275K 16-33
First 32 bit Intel processor , referred to as IA32
Added “flat addressing”, capable of running Unix
Pentium 4E 2004 125M 2800-3800
First 64-bit Intel x86 processor, referred to as x86-64
Core 2 2006 291M 1060-3500
First multi-core Intel processor
Core i7 2008 731M 1700-3900
Four cores (our shark machines)
5. Carnegie Mellon
5
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Intel x86 Processors, cont.
Machine Evolution
386 1985 0.3M
Pentium 1993 3.1M
Pentium/MMX 1997 4.5M
PentiumPro 1995 6.5M
Pentium III 1999 8.2M
Pentium 4 2001 42M
Core 2 Duo 2006 291M
Core i7 2008 731M
Added Features
Instructions to support multimedia operations
Instructions to enable more efficient conditional operations
Transition from 32 bits to 64 bits
More cores
6. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
2015 State of the Art
Core i7 Broadwell 2015
Desktop Model
4 cores
Integrated graphics
3.3-3.8 GHz
65W
Server Model
8 cores
Integrated I/O
2-2.6 GHz
45W
7. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
x86 Clones: Advanced Micro Devices
(AMD)
Historically
AMD has followed just behind Intel
A little bit slower, a lot cheaper
Then
Recruited top circuit designers from Digital Equipment Corp. and
other downward trending companies
Built Opteron: tough competitor to Pentium 4
Developed x86-64, their own extension to 64 bits
Recent Years
Intel got its act together
Leads the world in semiconductor technology
AMD has fallen behind
Relies on external semiconductor manufacturer
8. Carnegie Mellon
8
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Intel’s 64-Bit History
2001: Intel Attempts Radical Shift from IA32 to IA64
Totally different architecture (Itanium)
Executes IA32 code only as legacy
Performance disappointing
2003: AMD Steps in with Evolutionary Solution
x86-64 (now called “AMD64”)
Intel Felt Obligated to Focus on IA64
Hard to admit mistake or that AMD is better
2004: Intel Announces EM64T extension to IA32
Extended Memory 64-bit Technology
Almost identical to x86-64!
All but low-end x86 processors support x86-64
But, lots of code still runs in 32-bit mode
9. Carnegie Mellon
9
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Our Coverage
IA32
The traditional x86
For 15/18-213: RIP, Summer 2015
x86-64
The standard
shark> gcc hello.c
shark> gcc –m64 hello.c
Presentation
Book covers x86-64
Web aside on IA32
We will only cover x86-64
10. Carnegie Mellon
10
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Today: Machine Programming I: Basics
History of Intel processors and architectures
C, assembly, machine code
Assembly Basics: Registers, operands, move
Arithmetic & logical operations
11. Carnegie Mellon
11
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Definitions
Architecture: (also ISA: instruction set architecture) The
parts of a processor design that one needs to understand
or write assembly/machine code.
Examples: instruction set specification, registers.
Microarchitecture: Implementation of the architecture.
Examples: cache sizes and core frequency.
Code Forms:
Machine Code: The byte-level programs that a processor executes
Assembly Code: A text representation of machine code
Example ISAs:
Intel: x86, IA32, Itanium, x86-64
ARM: Used in almost all mobile phones
12. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
CPU
Assembly/Machine Code View
Programmer-Visible State
PC: Program counter
Address of next instruction
Called “RIP” (x86-64)
Register file
Heavily used program data
Condition codes
Store status information about most
recent arithmetic or logical operation
Used for conditional branching
PC
Registers
Memory
Code
Data
Stack
Addresses
Data
Instructions
Condition
Codes
Memory
Byte addressable array
Code and user data
Stack to support procedures
13. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
text
text
binary
binary
Compiler (gcc –Og -S)
Assembler (gcc or as)
Linker (gcc or ld)
C program (p1.c p2.c)
Asm program (p1.s p2.s)
Object program (p1.o p2.o)
Executable program (p)
Static libraries
(.a)
Turning C into Object Code
Code in files p1.c p2.c
Compile with command: gcc –Og p1.c p2.c -o p
Use basic optimizations (-Og) [New to recent versions of GCC]
Put resulting binary in file p
14. Carnegie Mellon
14
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Compiling Into Assembly
C Code (sum.c)
long plus(long x, long y);
void sumstore(long x, long y,
long *dest)
{
long t = plus(x, y);
*dest = t;
}
Generated x86-64 Assembly
sumstore:
pushq %rbx
movq %rdx, %rbx
call plus
movq %rax, (%rbx)
popq %rbx
ret
Obtain (on shark machine) with command
gcc –Og –S sum.c
Produces file sum.s
Warning: Will get very different results on non-Shark
machines (Andrew Linux, Mac OS-X, …) due to different
versions of gcc and different compiler settings.
15. Carnegie Mellon
15
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Assembly Characteristics: Data Types
“Integer” data of 1, 2, 4, or 8 bytes
Data values
Addresses (untyped pointers)
Floating point data of 4, 8, or 10 bytes
Code: Byte sequences encoding series of instructions
No aggregate types such as arrays or structures
Just contiguously allocated bytes in memory
16. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Assembly Characteristics: Operations
Perform arithmetic function on register or memory data
Transfer data between memory and register
Load data from memory into register
Store register data into memory
Transfer control
Unconditional jumps to/from procedures
Conditional branches
17. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Code for sumstore
0x0400595:
0x53
0x48
0x89
0xd3
0xe8
0xf2
0xff
0xff
0xff
0x48
0x89
0x03
0x5b
0xc3
Object Code
Assembler
Translates .s into .o
Binary encoding of each instruction
Nearly-complete image of executable code
Missing linkages between code in different
files
Linker
Resolves references between files
Combines with static run-time libraries
E.g., code for malloc, printf
Some libraries are dynamically linked
Linking occurs when program begins
execution
• Total of 14 bytes
• Each instruction
1, 3, or 5 bytes
• Starts at address
0x0400595
18. Carnegie Mellon
18
Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Machine Instruction Example
C Code
Store value t where designated by
dest
Assembly
Move 8-byte value to memory
Quad words in x86-64 parlance
Operands:
t: Register %rax
dest: Register %rbx
*dest: MemoryM[%rbx]
Object Code
3-byte instruction
Stored at address 0x40059e
*dest = t;
movq %rax, (%rbx)
0x40059e: 48 89 03
19. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Disassembled
Disassembling Object Code
Disassembler
objdump –d sum
Useful tool for examining object code
Analyzes bit pattern of series of instructions
Produces approximate rendition of assembly code
Can be run on either a.out (complete executable) or .o file
0000000000400595 <sumstore>:
400595: 53 push %rbx
400596: 48 89 d3 mov %rdx,%rbx
400599: e8 f2 ff ff ff callq 400590 <plus>
40059e: 48 89 03 mov %rax,(%rbx)
4005a1: 5b pop %rbx
4005a2: c3 retq
20. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Disassembled
Dump of assembler code for function sumstore:
0x0000000000400595 <+0>: push %rbx
0x0000000000400596 <+1>: mov %rdx,%rbx
0x0000000000400599 <+4>: callq 0x400590 <plus>
0x000000000040059e <+9>: mov %rax,(%rbx)
0x00000000004005a1 <+12>:pop %rbx
0x00000000004005a2 <+13>:retq
Alternate Disassembly
Within gdb Debugger
gdb sum
disassemble sumstore
Disassemble procedure
x/14xb sumstore
Examine the 14 bytes starting at sumstore
Object
0x0400595:
0x53
0x48
0x89
0xd3
0xe8
0xf2
0xff
0xff
0xff
0x48
0x89
0x03
0x5b
0xc3
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
What Can be Disassembled?
Anything that can be interpreted as executable code
Disassembler examines bytes and reconstructs assembly source
% objdump -d WINWORD.EXE
WINWORD.EXE: file format pei-i386
No symbols in "WINWORD.EXE".
Disassembly of section .text:
30001000 <.text>:
30001000: 55 push %ebp
30001001: 8b ec mov %esp,%ebp
30001003: 6a ff push $0xffffffff
30001005: 68 90 10 00 30 push $0x30001090
3000100a: 68 91 dc 4c 30 push $0x304cdc91
Reverse engineering forbidden by
Microsoft End User License Agreement
22. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Today: Machine Programming I: Basics
History of Intel processors and architectures
C, assembly, machine code
Assembly Basics: Registers, operands, move
Arithmetic & logical operations
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Some History: IA32 Registers
%eax
%ecx
%edx
%ebx
%esi
%edi
%esp
%ebp
%ax
%cx
%dx
%bx
%si
%di
%sp
%bp
%ah
%ch
%dh
%bh
%al
%cl
%dl
%bl
16-bit virtual registers
(backwards compatibility)
general
purpose
accumulate
counter
data
base
source
index
destination
index
stack
pointer
base
pointer
Origin
(mostly obsolete)
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Moving Data
Moving Data
movq Source, Dest:
Operand Types
Immediate: Constant integer data
Example: $0x400, $-533
Like C constant, but prefixed with ‘$’
Encoded with 1, 2, or 4 bytes
Register: One of 16 integer registers
Example: %rax, %r13
But %rsp reserved for special use
Others have special uses for particular instructions
Memory: 8 consecutive bytes of memory at address given by register
Simplest example: (%rax)
Various other “address modes”
%rax
%rcx
%rdx
%rbx
%rsi
%rdi
%rsp
%rbp
%rN
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
movq Operand Combinations
Cannot do memory-memory transfer with a single instruction
movq
Imm
Reg
Mem
Reg
Mem
Reg
Mem
Reg
Source Dest C Analog
movq $0x4,%rax temp = 0x4;
movq $-147,(%rax) *p = -147;
movq %rax,%rdx temp2 = temp1;
movq %rax,(%rdx) *p = temp;
movq (%rax),%rdx temp = *p;
Src,Dest
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Simple Memory Addressing Modes
Normal (R) Mem[Reg[R]]
Register R specifies memory address
Aha! Pointer dereferencing in C
movq (%rcx),%rax
Displacement D(R) Mem[Reg[R]+D]
Register R specifies start of memory region
Constant displacement D specifies offset
movq 8(%rbp),%rdx
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Example of Simple Addressing Modes
void swap
(long *xp, long *yp)
{
long t0 = *xp;
long t1 = *yp;
*xp = t1;
*yp = t0;
}
swap:
movq (%rdi), %rax
movq (%rsi), %rdx
movq %rdx, (%rdi)
movq %rax, (%rsi)
ret
29. Carnegie Mellon
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%rdi
%rsi
%rax
%rdx
Understanding Swap()
void swap
(long *xp, long *yp)
{
long t0 = *xp;
long t1 = *yp;
*xp = t1;
*yp = t0;
}
Memory
Register Value
%rdi xp
%rsi yp
%rax t0
%rdx t1
swap:
movq (%rdi), %rax # t0 = *xp
movq (%rsi), %rdx # t1 = *yp
movq %rdx, (%rdi) # *xp = t1
movq %rax, (%rsi) # *yp = t0
ret
Registers
35. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Simple Memory Addressing Modes
Normal (R) Mem[Reg[R]]
Register R specifies memory address
Aha! Pointer dereferencing in C
movq (%rcx),%rax
Displacement D(R) Mem[Reg[R]+D]
Register R specifies start of memory region
Constant displacement D specifies offset
movq 8(%rbp),%rdx
36. Carnegie Mellon
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Complete Memory Addressing Modes
Most General Form
D(Rb,Ri,S) Mem[Reg[Rb]+S*Reg[Ri]+ D]
D: Constant “displacement” 1, 2, or 4 bytes
Rb: Base register: Any of 16 integer registers
Ri: Index register: Any, except for %rsp
S: Scale: 1, 2, 4, or 8 (why these numbers?)
Special Cases
(Rb,Ri) Mem[Reg[Rb]+Reg[Ri]]
D(Rb,Ri) Mem[Reg[Rb]+Reg[Ri]+D]
(Rb,Ri,S) Mem[Reg[Rb]+S*Reg[Ri]]
38. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Today: Machine Programming I: Basics
History of Intel processors and architectures
C, assembly, machine code
Assembly Basics: Registers, operands, move
Arithmetic & logical operations
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Carnegie Mellon
Address Computation Instruction
leaq Src, Dst
Src is address mode expression
Set Dst to address denoted by expression
Uses
Computing addresses without a memory reference
E.g., translation of p = &x[i];
Computing arithmetic expressions of the form x + k*y
k = 1, 2, 4, or 8
Example
long m12(long x)
{
return x*12;
}
leaq (%rdi,%rdi,2), %rax # t <- x+x*2
salq $2, %rax # return t<<2
Converted to ASM by compiler:
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Carnegie Mellon
Some Arithmetic Operations
Two Operand Instructions:
Format Computation
addq Src,Dest Dest = Dest + Src
subq Src,Dest Dest = Dest Src
imulq Src,Dest Dest = Dest * Src
salq Src,Dest Dest = Dest << Src Also called shlq
sarq Src,Dest Dest = Dest >> Src Arithmetic
shrq Src,Dest Dest = Dest >> Src Logical
xorq Src,Dest Dest = Dest ^ Src
andq Src,Dest Dest = Dest & Src
orq Src,Dest Dest = Dest | Src
Watch out for argument order!
No distinction between signed and unsigned int (why?)
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Carnegie Mellon
Some Arithmetic Operations
One Operand Instructions
incq Dest Dest = Dest + 1
decq Dest Dest = Dest 1
negq Dest Dest = Dest
notq Dest Dest = ~Dest
See book for more instructions
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Carnegie Mellon
Arithmetic Expression Example
Interesting Instructions
leaq: address computation
salq: shift
imulq: multiplication
But, only used once
long arith
(long x, long y, long z)
{
long t1 = x+y;
long t2 = z+t1;
long t3 = x+4;
long t4 = y * 48;
long t5 = t3 + t4;
long rval = t2 * t5;
return rval;
}
arith:
leaq (%rdi,%rsi), %rax
addq %rdx, %rax
leaq (%rsi,%rsi,2), %rdx
salq $4, %rdx
leaq 4(%rdi,%rdx), %rcx
imulq %rcx, %rax
ret
43. Carnegie Mellon
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Carnegie Mellon
Understanding Arithmetic Expression
Example
long arith
(long x, long y, long z)
{
long t1 = x+y;
long t2 = z+t1;
long t3 = x+4;
long t4 = y * 48;
long t5 = t3 + t4;
long rval = t2 * t5;
return rval;
}
arith:
leaq (%rdi,%rsi), %rax # t1
addq %rdx, %rax # t2
leaq (%rsi,%rsi,2), %rdx
salq $4, %rdx # t4
leaq 4(%rdi,%rdx), %rcx # t5
imulq %rcx, %rax # rval
ret
Register Use(s)
%rdi Argument x
%rsi Argument y
%rdx Argument z
%rax t1, t2, rval
%rdx t4
%rcx t5
44. Carnegie Mellon
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Bryant and O’Hallaron, Computer Systems: A Programmer’s Perspective, Third Edition
Machine Programming I: Summary
History of Intel processors and architectures
Evolutionary design leads to many quirks and artifacts
C, assembly, machine code
New forms of visible state: program counter, registers, ...
Compiler must transform statements, expressions, procedures into
low-level instruction sequences
Assembly Basics: Registers, operands, move
The x86-64 move instructions cover wide range of data movement
forms
Arithmetic
C compiler will figure out different instruction combinations to
carry out computation