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Dynamic Dead Code Elimination
In compiler theory, dead-code elimination (also known as DCE, dead-code removal, dead-code stripping, or dead-code strip) is a compiler optimization to remove code which does not affect the program results. Removing such code has several benefits: it shrinks program size, an important consideration in some contexts, and it allows the running program to avoid executing irrelevant operations, which reduces its running time. It can also enable further optimizations by simplifying program structure. ''Dead code'' includes code that can never be executed ('' unreachable code''), and code that only affects '' dead variables'' (written to, but never read again), that is, irrelevant to the program. Examples Consider the following example written in C. int foo(void) Simple analysis of the uses of values would show that the value of b after the first assignment is not used inside foo. Furthermore, b is declared as a local variable inside foo, so its value cannot be used outside foo. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compiler Theory
In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that translate source code from a high-level programming language to a low-level programming language (e.g. assembly language, object code, or machine code) to create an executable program. Compilers: Principles, Techniques, and Tools by Alfred V. Aho, Ravi Sethi, Jeffrey D. Ullman - Second Edition, 2007 There are many different types of compilers which produce output in different useful forms. A ''cross-compiler'' produces code for a different CPU or operating system than the one on which the cross-compiler itself runs. A ''bootstrap compiler'' is often a temporary compiler, used for compiling a more permanent or better optimised compiler for a language. Related software include, a program that translates from a low-level language to a h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Load Time
In computer systems a loader is the part of an operating system that is responsible for loading programs and libraries. It is one of the essential stages in the process of starting a program, as it places programs into memory and prepares them for execution. Loading a program involves memory-mapping the contents of the executable file containing the program instructions into memory, and then carrying out other required preparatory tasks to prepare the executable for running. Once loading is complete, the operating system starts the program by passing control to the loaded program code. All operating systems that support program loading have loaders, apart from highly specialized computer systems that only have a fixed set of specialized programs. Embedded systems typically do not have loaders, and instead, the code executes directly from ROM or similar. In order to load the operating system itself, as part of booting, a specialized boot loader is used. In many operating system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Software Updating
In computer science, dynamic software updating (DSU) is a field of research pertaining to upgrading programs while they are running. DSU is not currently widely used in industry. However, researchers have developed a wide variety of systems and techniques for implementing DSU. These systems are commonly tested on real-world programs. Current operating systems and programming languages are typically not designed with DSU in mind. As such, DSU implementations commonly either utilize existing tools, or implement specialty compilers. These compilers preserve the semantics of the original program, but instrument either the source code or object code to produce a dynamically updateable program. Researchers compare DSU-capable variants of programs to the original program to assess safety and performance overhead. Introduction Any running program can be thought of a tuple (\delta, P), where \delta is the current program state and P is the current program code. Dynamic software updating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conjunction Elimination
In propositional logic, conjunction elimination (also called ''and'' elimination, ∧ elimination, or simplification)Hurley is a valid immediate inference, argument form and rule of inference which makes the inference that, if the conjunction ''A and B'' is true, then ''A'' is true, and ''B'' is true. The rule makes it possible to shorten longer proofs by deriving one of the conjuncts of a conjunction on a line by itself. An example in English: :It's raining and it's pouring. :Therefore it's raining. The rule consists of two separate sub-rules, which can be expressed in formal language as: :\frac and :\frac The two sub-rules together mean that, whenever an instance of "P \land Q" appears on a line of a proof, either "P" or "Q" can be placed on a subsequent line by itself. The above example in English is an application of the first sub-rule. Formal notation The ''conjunction elimination'' sub-rules may be written in sequent notation: : (P \land Q) \vdash P and : (P \lan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Partial-redundancy Elimination
In compiler theory, partial redundancy elimination (PRE) is a compiler optimization that eliminates expressions that are redundant on some but not necessarily all paths through a program. PRE is a form of common subexpression elimination. An expression is called partially redundant if the value computed by the expression is already available on some but not all paths through a program to that expression. An expression is fully redundant if the value computed by the expression is available on all paths through the program to that expression. PRE can eliminate partially redundant expressions by inserting the partially redundant expression on the paths that do not already compute it, thereby making the partially redundant expression fully redundant. For instance, in the following code: if (some_condition) else z = x + 4; the expression x+4 assigned to z is partially redundant because it is computed twice if some_condition is true. PRE would perform code motion on the ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simplification (symbolic Computation)
In mathematics and computer science, computer algebra, also called symbolic computation or algebraic computation, is a scientific area that refers to the study and development of algorithms and software for manipulating mathematical expressions and other mathematical objects. Although computer algebra could be considered a subfield of scientific computing, they are generally considered as distinct fields because scientific computing is usually based on numerical computation with approximate floating point numbers, while symbolic computation emphasizes ''exact'' computation with expressions containing variables that have no given value and are manipulated as symbols. Software applications that perform symbolic calculations are called ''computer algebra systems'', with the term ''system'' alluding to the complexity of the main applications that include, at least, a method to represent mathematical data in a computer, a user programming language (usually different from the langua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redundant Code
In computer programming, redundant code is source code or compiled code in a computer program that is unnecessary, such as: * recomputing a value that has previously been calculated and is still available, * code that is never executed (known as unreachable code), * code which is executed but has no external effect (e.g., does not change the output produced by a program; known as dead code). A NOP instruction might be considered to be redundant code that has been explicitly inserted to pad out the instruction stream or introduce a time delay, for example to create a timing loop by "wasting time". Identifiers that are declared, but never referenced, are termed redundant declarations. Examples The following examples are in C. int foo(int iX) The second iX*2 expression is redundant code and can be replaced by a reference to the variable iY. Alternatively, the definition int iY = iX*2 can instead be removed. Consider: #define min(A,B) ((A)(B)?(A):(B)) int random(int cuto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hot Patching
Hot or the acronym HOT may refer to: Food and drink *Pungency, in food, a spicy or hot quality *Hot, a wine tasting descriptor Places * Hot district, a district of Chiang Mai province, Thailand **Hot subdistrict, a sub-district of Hot District, Thailand **Tha Kham, Chiang Mai, also known as Hot, a town in Hot District, Chiang Mai province, Thailand *Hot, Albania, a village in the Malësi e Madhe municipality, Shkodër County, Albania Music *H.O.T. pronounced "H. O. T.", (High-Five of Teenagers), a South Korean boy band *Hawaii Opera Theatre, an opera company in Honolulu, Hawaii * Hot (American vocal group), best known for 1977 hit "Angel in Your Arms" 1976–1980 *Hot 97, branding for hip-hop radio station WQHT in New York City Albums * ''Hot'' (Freda Payne album), 1979 * ''Hot'' (Half Japanese album), 1995 * ''Hot'' (Inna album) or the title song (see below), 2009 * ''Hot'' (James Brown album) or the title song (see below), 1976 * ''Hot'' (Mel B album), 2000 * ''Hot'' (Paul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Software Updating
In computer science, dynamic software updating (DSU) is a field of research pertaining to upgrading programs while they are running. DSU is not currently widely used in industry. However, researchers have developed a wide variety of systems and techniques for implementing DSU. These systems are commonly tested on real-world programs. Current operating systems and programming languages are typically not designed with DSU in mind. As such, DSU implementations commonly either utilize existing tools, or implement specialty compilers. These compilers preserve the semantics of the original program, but instrument either the source code or object code to produce a dynamically updateable program. Researchers compare DSU-capable variants of programs to the original program to assess safety and performance overhead. Introduction Any running program can be thought of a tuple (\delta, P), where \delta is the current program state and P is the current program code. Dynamic software updating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Just-in-time Compilation
In computing, just-in-time (JIT) compilation (also dynamic translation or run-time compilations) is a way of executing computer code that involves compilation during execution of a program (at run time) rather than before execution. This may consist of source code translation but is more commonly bytecode translation to machine code, which is then executed directly. A system implementing a JIT compiler typically continuously analyses the code being executed and identifies parts of the code where the speedup gained from compilation or recompilation would outweigh the overhead of compiling that code. JIT compilation is a combination of the two traditional approaches to translation to machine code—ahead-of-time compilation (AOT), and interpretation—and combines some advantages and drawbacks of both. Roughly, JIT compilation combines the speed of compiled code with the flexibility of interpretation, with the overhead of an interpreter and the additional overhead of compi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Assembly Language
In computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence between the instructions in the language and the architecture's machine code instructions. Assembly language usually has one statement per machine instruction (1:1), but constants, comments, assembler directives, symbolic labels of, e.g., memory locations, registers, and macros are generally also supported. The first assembly code in which a language is used to represent machine code instructions is found in Kathleen and Andrew Donald Booth's 1947 work, ''Coding for A.R.C.''. Assembly code is converted into executable machine code by a utility program referred to as an '' assembler''. The term "assembler" is generally attributed to Wilkes, Wheeler and Gill in their 1951 book '' The Preparation of Programs for an Electronic Di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ahead-of-time Compilation
In computer science, ahead-of-time compilation (AOT compilation) is the act of compiling an (often) higher-level programming language into an (often) lower-level language before execution of a program, usually at build-time, to reduce the amount of work needed to be performed at run time. Most often, It is associated with the act of compiling a higher-level programming language such as C or C++, or an intermediate representation such as Java bytecode or .NET Framework Common Intermediate Language (CIL) code, into a native (system-dependent) machine code so that the resulting binary file can execute natively, just like a ''standard'' native compiler. When being used in this specific context, it's often seen as an opposite of just-in-time (JIT) compiling. Speaking more generally, the target languages of an AOT compilation are not necessarily specific to native machine code but are defined rather arbitrarily. Some academic papers use this word to mean the act of compiling the Jav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
