File Name: code optimization and code generation in compiler design .zip
Search IDA. Goals Give Ph. Prerequisites Basic course in compiler construction, corresponding to the undergraduate courses Compilers and Interpreters or Compiler Construction.
This section contains selected lecture notes. Audio and video lectures from a previous semester can be found in the 6.
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Code optimization is any method of code modification to improve code quality and efficiency. The basic requirements optimization methods should comply with, is that an optimized program must have the same output and side effects as its non-optimized version. This requirement, however, may be ignored in the case that the benefit from optimization, is estimated to be more important than probable consequences of a change in the program behavior.
Optimization can be performed by automatic optimizers, or programmers. An optimizer is either a specialized software tool or a built-in unit of a compiler the so-called optimizing compiler. Modern processors can also optimize the execution order of code instructions. Optimizations are classified into high-level and low-level optimizations. High-level optimizations are usually performed by the programmer, who handles abstract entities functions, procedures, classes, etc.
Optimizations performed at the level of elementary structural blocks of source code - loops, branches, etc. Low-level optimizations are performed at the stage when source code is compiled into a set of machine instructions, and it is at this stage that automated optimization is usually employed.
Assembler programmers believe however, that no machine, however perfect, can do this better than a skilled programmer yet everybody agrees that a poor programmer will do much worse than a computer. With manual code optimization, one faces another problem: one doesn't just need to know how exactly optimization should be done, but also what particular part of the program should be optimized.
Tanenbaum makes it sound convincing. These code fragments are known as bottlenecks, and can be detected by special utilities - profilers - which can measure the time taken by various parts of the program to execute. In practice, however, optimization is usually done after the stage of "chaotic" programming including such methods as " Copy-Paste ", "we'll see later", "it's OK this way" , and therefore is a mixture of optimization as such, refactoring and bugfixes : simplification of "queer" constructs like strlen path.
Profilers are of little help with this kind of optimization. Nevertheless, you can detect these issues with static analysis tools, i. As you can see from the above mentioned example with the strange condition, inefficient code may appear as a result of errors like a misprint in our example, where a.
A powerful static analyzer will detect such code fragments and draw your attention to them by producing warning messages. In programming, almost everything should be treated from the viewpoint of rationality - optimization is no exception. There is a belief that code written by an inexperienced Assembler programmer is times slower than code generated by the compiler Zubkov.
Widely known is a phrase by Knuth regarding early low-level optimizations such as attempts to save on operators or variables : "Premature optimization is the root of all evil".
Most programmers don't complain about optimizations performed by the optimizer, some of which are conventional and obligatory. Such as, for instance, tail call optimization in functional languages tail call is a special case of recursion, which can be represented as a loop. However, one should understand that multiple complex optimizations at the level of machine code may cause a great slow-down of compilation.
The benefit they allow you to gain may be much too insignificant, when compared to general system design optimizations Wirth. One should also keep in mind that modern languages, with all their syntactic and semantic "frills", have many nuances and subtleties, so that a programmer who isn't familiar with them may be surprised by an outcome of optimization.
Because the compiler omits copying, this method is also called "Copy elision". So, the following code:. Thus, we should always consider optimizing the program code using specialized utilities wherever possible, yet do this with much care, and be ready for the probability of unexpected tricks from the compiler at times.
A set of diagnostics is implemented in the static analyzer PVS-Studio that enable you to find some situations where code can be optimized. However, PVS-Studio as any other static analyzer cannot serve as a replacement of the profiling tools. Only dynamic program analyzers are able to identify the bottlenecks. Static analyzers do not know what input data programs get and how often a particular piece of code is executed.
That is why we are saying that the analyzer suggests implementing some "micro-optimizations" of code, which do not guarantee the performance gains. Despite the considered disadvantage, PVS-Studio analyzer acts as a good complement to profiling tools. Moreover, when dealing with PVS-Studio warnings, related to optimization, code often becomes simpler and shorter. This effect is considered in more detail in the article " Exploring Microoptimizations Using Tizen Code as an Example ".
Users sometimes ask how new diagnostics appear in the PVS-Studio static analyzer. We answer that we draw inspiration from a Episode of CppCast was recorded on January 6th, Anyone who's ever dealt with information security What does this word mean to you?
Nowadays, companies spare no effort to ensure that their product is secured Static analysis helps developers catch errors early and improve code quality and reliability. This article examines some potential vulnerabilities and BlameNotifier utility. Types and Levels of Optimization Optimization can be performed by automatic optimizers, or programmers. What to Optimize With manual code optimization, one faces another problem: one doesn't just need to know how exactly optimization should be done, but also what particular part of the program should be optimized.
Good and Bad Outcomes of Optimization In programming, almost everything should be treated from the viewpoint of rationality - optimization is no exception. A copy was made. Hello World! Conclusion Thus, we should always consider optimizing the program code using specialized utilities wherever possible, yet do this with much care, and be ready for the probability of unexpected tricks from the compiler at times.
References A. Structured Computer Organization. Compiler Construction. Zubkov S. Code optimization. Optimizing compiler. Copy elision.
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In computing , code generation is the process by which a compiler 's code generator converts some intermediate representation of source code into a form e. Sophisticated compilers typically perform multiple passes over various intermediate forms. This multi-stage process is used because many algorithms for code optimization are easier to apply one at a time, or because the input to one optimization relies on the completed processing performed by another optimization. This organization also facilitates the creation of a single compiler that can target multiple architectures, as only the last of the code generation stages the backend needs to change from target to target. For more information on compiler design, see Compiler. The input to the code generator typically consists of a parse tree or an abstract syntax tree.
The code optimization in the synthesis phase is a program transformation technique, which tries to improve the intermediate code by making it consume fewer resources i. CPU, Memory so that faster-running machine code will result. Compiler optimizing process should meet the following objectives :. When to Optimize? Optimization of the code is often performed at the end of the development stage since it reduces readability and adds code that is used to increase the performance.
COMPILER DESIGN. UNIT V. Optimization A code optimizing process must follow the three rules given below: 1. The output After generating intermediate code, the compiler can modify the intermediate code by address calculations and.
Code optimization is any method of code modification to improve code quality and efficiency. The basic requirements optimization methods should comply with, is that an optimized program must have the same output and side effects as its non-optimized version. This requirement, however, may be ignored in the case that the benefit from optimization, is estimated to be more important than probable consequences of a change in the program behavior. Optimization can be performed by automatic optimizers, or programmers.
Both the course webpage and moodle may be frequently updated; please check them regularly. Course Description This course uses compilers as example to expose students to modern software development techniques. The course introduces the students to the fundamentals of compiler construction. Students will implement a simple yet complete compiler for an object-oriented programming language for a realistic target machine. Students will learn the use of appropriate tools.
Eventually you learned to look old friends straight in the eye and say, one of the dozen witnesses. This course on compiler design is to address all these issues, starting from the theoretical foundations to the architectural issues to automated tools. Feb 27, textbook of psychotherapeutic treatments in psychiatry They were paranoid of everyone and were sure people were staring at them. Not once did she come here that late at night. Updated to include the latest techniques, The Compiler Design Handbook, Second Edition offers a unique opportunity for designers and researchers to update their knowledge, refine their skills, and prepare for emerging innovations.
Запускайте видеозапись. ГЛАВА 117 - Трансляция видеофильма начнется через десять секунд, - возвестил трескучий голос агента Смита. - Мы опустим каждый второй кадр вместе со звуковым сопровождением и постараемся держаться как можно ближе к реальному времени. На подиуме все замолчали, не отрывая глаз от экрана. Джабба нажал на клавиатуре несколько клавиш, и картинка на экране изменилась. В левом верхнем углу появилось послание Танкадо: ТЕПЕРЬ ВАС МОЖЕТ СПАСТИ ТОЛЬКО ПРАВДА Правая часть экрана отображала внутренний вид мини-автобуса и сгрудившихся вокруг камеры Беккера и двух агентов.
Она испуганно посмотрела на вращающуюся дверь… как бы прикидывая расстояние. До выхода было метров тридцать. - Я оплачу тебе билет до дома, если… - Молчите, - сказала Меган с кривой улыбкой. - Я думаю, я поняла, что вам от меня. - Она наклонилась и принялась рыться в сумке.
И Сьюзан принялась объяснять, как Хейл отозвал Следопыта и как она обнаружила электронную почту Танкадо, отправленную на адрес Хейла. Снова воцарилось молчание. Стратмор покачал головой, отказываясь верить тому, что услышал. - Не может быть, чтобы Грег Хейл был гарантом затеи Танкадо. Это полный абсурд.
Да, я была с ним слишком сурова, - подумала Сьюзан. Ее мысли были прерваны внезапным звуковым сигналом входной двери Третьего узла. Стратмор чуть ли не вбежал в комнату. - Сьюзан, - сказал он, - только что позвонил Дэвид. Он задерживается.
Часть задания заключалась в немедленном уведомлении. Но сообщать имена жертв… с точки зрения человека в очках в металлической оправе, это было признаком особой элегантности стиля. Его пальцы снова задвигались, приводя в действие сотовый модем, и перед глазами появилось: СООБЩЕНИЕ ОТПРАВЛЕНО ГЛАВА 26 Сидя на скамейке напротив городской больницы, Беккер думал о том, что делать. Звонки в агентства услуг сопровождения ничего не дали.