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We will start by taking a walk through an optimizing compiler to see one at work. We think it’s interesting, and if you can empathize with the compiler, you will be a better programmer; you will know what the compiler wants from you, and what it can do on its own.

Compilation process

Basic compiler processes

This figure is a flowchart showing movement from numerous lines of code to numerous boxes. From the beginning is a group of code, the first line showing A=B*C+5, and the second line D=B*C. From the bottom of this group of code is a line pointing to a box labeled Lexical Analysis. Below this is a line pointing to a line of code, A=B*C+5. The A is labeled variable, the * is labeled Operator, and the 5 is labeled constant. Below this line of code is an arrow pointing down at a box labeled Parse. Below this box is a grouping of code. The first line reads, T1:=B*C, the second line reads, A:=T1+5, and the third line reads D:=B*C. Pointing towards the upper-right is an arrow that points at a box labeled Optimization.

The compilation process is typically broken down into a number of identifiable steps, as shown in [link] . While not all compilers are implemented in exactly this way, it helps to understand the different functions a compiler must perform:

  1. A precompiler or preprocessor phase is where some simple textual manipulation of the source code is performed. The preprocessing step can be processing of include files and making simple string substitutions throughout the code.
  2. The lexical analysis phase is where the incoming source statements are decomposed into tokens such as variables, constants, comments, or language elements.
  3. The parsing phase is where the input is checked for syntax, and the compiler translates the incoming program into an intermediate language that is ready for optimization.
  4. One or more optimization passes are performed on the intermediate language.
  5. An object code generator translates the intermediate language into assembly code, taking into consideration the particular architectural details of the processor in question.

As compilers become more and more sophisticated in order to wring the last bit of performance from the processor, some of these steps (especially the optimization and code-generation steps) become more and more blurred. In this chapter, we focus on the traditional optimizing compiler, and in later chapters we will look more closely at how modern compilers do more sophisticated optimizations.

Intermediate language representation

Because we are most interested in the optimization of our program, we start our discussion at the output of the parse phase of the compiler. The parse phase output is in the form of an an intermediate language (IL) that is somewhere between a high-level language and assembly language. The intermediate language expresses the same calculations that were in the original program, in a form the compiler can manipulate more easily. Furthermore, instructions that aren’t present in the source, such as address expressions for array references, become visible along with the rest of the program, making them subject to optimizations too.

How would an intermediate language look? In terms of complexity, it’s similar to assembly code but not so simple that the definitions By “definitions,” we mean the assignment of values: not declarations. and uses of variables are lost. We’ll need definition and use information to analyze the flow of data through the program. Typically, calculations are expressed as a stream of quadruples — statements with exactly one operator, (up to) two operands, and a result. More generally, code can be cast as n -tuples. It depends on the level of the intermediate language. Presuming that anything in the original source program can be recast in terms of quadruples, we have a usable intermediate language. To give you an idea of how this works, We’re going to rewrite the statement below as a series of four quadruples:

Questions & Answers

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, High performance computing. OpenStax CNX. Aug 25, 2010 Download for free at http://cnx.org/content/col11136/1.5
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