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Topic: Dead code elimination

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	Dead Code Elimination With the Link-Editor in the Solaris OS
		This process of concatenation may result in an output that includes one or more unused functions (dead code) and is larger than necessary.
		Unused section elimination in the link-editor is enabled with the
		Unless otherwise licensed, code in all technical manuals herein (including articles, FAQs, samples) is provided under this License.
	developers.sun.com /solaris/articles/deadcode_ld.html (734 words)

	Dead code elimination -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-06)
		In (additional info and facts about compiler theory) compiler theory, dead code elimination is a (additional info and facts about compiler optimization) compiler optimization used to reduce program size by removing code which can never be executed (known as dead or (additional info and facts about unreachable code) unreachable code).
		A common use of dead code elimination is as an alternative to optional code inclusion via a (additional info and facts about preprocessor) preprocessor.
		This technique is common in (additional info and facts about debugging) debugging to optionally activate blocks of code; using an optimizer with dead code elimination eliminates the need for using a (additional info and facts about preprocessor) preprocessor to perform the same task.
	www.absoluteastronomy.com /encyclopedia/d/de/dead_code_elimination.htm (452 words)

	Compiler article - Compiler computer program computer language Introduction history Types - What-Means.com (Site not responding. Last check: 2007-10-06)
		Most compilers translate source code written in a high level language to object code or machine language that may be directly executed by a computer or a virtual machine.
		A compiler may produce code intended to run on the same type of computer and operating system ("platform") as the compiler itself runs on.
		Code generation - the transformed intermediate language is translated into the output language, usually the native machine language of the system.
	www.what-means.com /encyclopedia/Compiler (1555 words)

	Compiler Optimization (Site not responding. Last check: 2007-10-06)
		Dead code elimination is the ability of the compiler to remove statements that it knows are `dead'.
		For our purposes, dead code can only be copies whose left hand side is not used again (ie, because of copy propagation, the copy is now dead).
		Dead code elimination may have to be repeated multiple times to catch all the dead copies.
	www.eecis.udel.edu /~breech/contest.inet.spring.00/problems/compiler-opt.html (678 words)

	Embedded Intel® Solutions (Site not responding. Last check: 2007-10-06)
		Using processor dispatch, the compiler inserts code to dispatch the call to a version of the Kasumi function dependent on the processor that is executing the application at runtime.
		Reduced code size is important in embedded applications, so employing techniques for reducing code size when using vectorization and processor dispatch is critical.
		Dead code elimination - increased interprocedural information enables detection of code that may be proven unreachable.
	www.embeddedintel.com /display.php?article=54 (1821 words)

	Code Optimization Using the GNU C Compiler LG #71 (Site not responding. Last check: 2007-10-06)
		Dead code is the code in the program that will never be executed for any input or other conditions.
		It has to keep track of various things like variables, their storage places (memory or registers), expression evaluations, constant expressions, dead code etc. It is because of this high complexity of the process that the compiler takes much longer to compile a program with optimization enabled.
		Code optimization is a field of active research and interested readers can refer to [1] for additional information.
	www.linuxgazette.com /issue71/joshi.html (2868 words)

	Compilers, Part 2: The Back End \| Linux Magazine
		Code is divided into basic blocks such that if the first statement in a block is executed, all the statements in that block are executed.
		Dead code can occur in many forms and some are easier for the compiler to find than others.
		Both inlining and loop unrolling may cause the size of code to grow and it may be inappropriate to inline all functions and unroll all loops.
	www.linux-mag.com /id/1112 (1641 words)

	Dead code (Site not responding. Last check: 2007-10-06)
		Even by using for the optimization of the code the level 1 " Dead codes elimination ", code is generated for the uncalled functions.
		Dead code elimination should work the same whether I build a lib or list a string of.obj's for the link.
		I'd suggest you need perhaps three levels: the current style; a "warnings only" where the linker merely notes that the code has been removed to nag you into getting to the final code yet without adding to the "program size" counters; and a silent option where the code disappears without any warning.
	www.keil.com /forum/docs/thread1701.asp (664 words)

	Dead Code Elimination (Site not responding. Last check: 2007-10-06)
		2] is an optimization technique to eliminate some variables not used at all.
		Since these control variables are often unused, and the methods are specialized methods known to the compiler--side effect free--we don't have any side effects from applying DCE with data flow analysis to them.
		We assume that DCE should be applied after all optimization techniques we discussed earlier.
	www.hpjava.org /papers/PAA-Special-04/hpjava/node15.html (102 words)

	Code Optimization Using the GNU C Compiler LG #71
		Dead code is the code in the program that will never be executed for any input or other conditions.
		It has to keep track of various things like variables, their storage places (memory or registers), expression evaluations, constant expressions, dead code etc. It is because of this high complexity of the process that the compiler takes much longer to compile a program with optimization enabled.
		Code optimization is a field of active research and interested readers can refer to [1] for additional information.
	www.tldp.org /LDP/LG/issue71/joshi.html (2868 words)

	[No title]
		This is where the code inside some methods is substituted for the calls to that method, eliminating the need to use memory to call and load that method.
		Method inlining is when the code inside a short or frequently called method is substituted for the call to the method, so that memory is not required to load and perform the method each time it is called.
		Dead code elimination is an optimization that allows a compiler or virtual machine to ignore code and variables that are never used.
	cda.mrs.umn.edu /~elenam/Caudill-MICS-corrected.doc (2352 words)

	compilers.net > paedia > compiler
		However, translation from a low level language to a high level one is also possible; this is normally known as a decompiler if it is reconstructing a high level language program which (could have) generated the low level language program.
		Certain languages, due to the design of the language and certain rules placed on the declaration of variables and other objects used, and the predeclaration of executable procedures prior to reference or use, are capable of being compiled in a single pass.
		Popular optimizations are in-line expansion, dead code elimination, constant propagation, loop transformation, register allocation or even auto parallelization.
	www.compilers.net /paedia/compiler/index.htm (1852 words)

	Dead-code elimination (Site not responding. Last check: 2007-10-06)
		The usual method for dead code elimination is to first locate all instructions that are useful in some sense.
		Typically, dead code elimination algorithms start by marking output instructions to be critical.
		Any code that is left unmarked is useless to the given computation.
	www.cs.uh.edu /~jhuang/JCH/ASE/slicing2/sld021.htm (67 words)

	Java theory and practice: Dynamic compilation and performance measurement
		Only compiling code that is executed frequently has several performance advantages: No time is wasted compiling code that will execute infrequently, and the compiler can, therefore, spend more time on optimization of hot code paths because it knows that the time will be well spent.
		It can perform many of the standard optimizations found in static compilers, such as code hoisting, common subexpression elimination, loop unrolling, range check elimination, dead-code elimination, and data-flow analysis, as well as a variety of optimizations that are not practical in statically compiled languages, such as aggressive inlining of virtual method invocations.
		If the compiler is going to optimize away a block of code because it reasons the code to be irrelevant (a common situation with benchmarks that don't actually do anything), you can see it in the generated machine code -- the code is not there.
	www-128.ibm.com /developerworks/java/library/j-jtp12214?ca=degr-L0260dyncompilation (3542 words)

	Dead Code Elimination (Site not responding. Last check: 2007-10-06)
		Code that is unreachable or that does not affect the program (e.g.
		The first assignment to global is dead, and the third assignment to global is unreachable; both can be eliminated.
		Below is the code fragment after dead code elimination.
	www.nullstone.com /htmls/category/deadcode.htm (103 words)

	Dead Code Elimination (Site not responding. Last check: 2007-10-06)
		All instructions that define a certain variable, which is not subsequently used, is dead.
		The data flow solver is used to solve a backward data flow problem of liveness of variables.
		The solution is used to eliminate all code that is found to be dead.
	www.cs.umd.edu /users/suman/docs/731s98/node8.html (75 words)

	5.3 Control-flow Optimizations
		Unreachable code is code that cannot possibly be executed, regardless of the input data.
		592, a variable is dead if it is not used on any path from the location in the code where it is defined to the exit point of the routine in the question ; an instruction is dead if it computes only values that are not used on any executable path leading from the instruction.
		This phase tries to generate finite state machine from arbitrary code by applying rules numeroting branches of the syntax tree and using it as state variable for the finite state machine.
	www.cri.ensmp.fr /PIPS/pipsmake-rc/node33.html (1297 words)

	: Package EDU.purdue.cs.bloat.trans
		Eliminate partially redundant local variable loads and stores by replacing them with stack variables and dups.
		Dead code elimination removes code from a method that does not contribute to the final output of the program.
		A value folder is then used to eliminate redundent nodes from and to propagate constants through the control flow graph.
	www.cs.purdue.edu /s3/projects/bloat/docs/api/EDU/purdue/cs/bloat/trans/package-summary.html (488 words)

	Real World Technologies - Compilers - Code Optimization
		This is dead, unreachable code, it is actually quite uncommon and rarely affects performance or code size.
		Common subexpression elimination is very important in array address calculations since some parts of the calculations can be reused.
		So dead code can be found by looking for nodes with no variables left alive.
	www.realworldtech.com /page.cfm?ArticleID=RWT110302111309&p=2 (533 words)

	COSC 6361 Class Projects (Site not responding. Last check: 2007-10-06)
		The task is to fully understand and test the Dead Code Elimination (DCE) algorithm in the Open64 compiler.
		Dead code elimination algorithms may eliminate code that is unreachable, will never be computed, or whose values do not contribute to the outcome of the code.
		Use one or more code examples to test the dead code elimination algorithm and understand how it changes the IR Study how to map the eliminated code from IR to source code in Open64, and dump the eliminated code information from the compiler
	www.cs.uh.edu /~hpctools/cosc6361/projects.html (1309 words)

	Red Hat \| GCC Optimization (Site not responding. Last check: 2007-10-06)
		GCC supports loop inversion, which eliminates some test, and branch code inside loops and, supports inversion of loop counter to count down to zero instead of up to a constant value.
		Reduced register pressure leads to more efficient code, particularly in routines where the number of user variables and compiler generated temporaries is larger than the physical register set for the target processor.
		Spill code moves data in/out of memory or in/out of special registers when a particular variable/compiler temporary did not get allocated to one of the target processor's registers.
	www.redhat.com /en_us/USA/home/gnupro/technicaldetails/gccoptimization (1168 words)

	Christopher Ogren
		Dead Code Elimination gets rid of statements that produce values that never get used or statements that can never be reached due to a value staying constant.
		Code motion takes code that is inside a loop and moves it outside of and before the loop.
		The way this table is works is that the loop is assumed to operate over I from 1 to n with the operation in the expression column appearing inside the loop.
	www.cs.engr.uky.edu /~jurek/cs541/Spring2002/files/ChrisOgrenLauraReynolds4.html (1615 words)

	IBM Software - IBM Asset Transformation Workbench - Componentization using the IBM Asset Transformation Workbench
		By eliminating this code, analysis and ongoing development is simplified.
		The challenge when dead code elimination is conducted manually is how to avoid destabilizing the application.
		Efficiently navigating through our code, we locate the rule we had previously identified and using the diagramming capabilities of ATW, we look at our code in more detail to reconfirm that this rule is suitable for componentization.
	www-306.ibm.com /software/awdtools/atw/library/component.html (966 words)

	CSc 553 : Programming Assignment 4 (Site not responding. Last check: 2007-10-06)
		You are to use the information obtained from your liveness analysis to eliminate dead code, i.e., code whose results are never used.
		A naive approach would be to repeat the liveness analysis all over again, eliminate some more dead code, and repeat the procedure.
		At the end of the analysis all instructions that are marked ``dead'' represent dead code, and can be eliminated.
	www.cs.arizona.edu /classes/cs553/spring04/ASSIGNMENTS/prog4.optimization.html (543 words)

	Experiments and Anlysis
		In general, doing dead code elimination the last would be a good idea, based on the assumption that since users do not generally write dead code, it would be wasteful doing that earlier.
		All optimization passes that I tested the code with, produced correct code, in as much that it gives the output as the un-optimized code.
		To show that dead code elimination indeed is an useful postphase for most optimizations, let us compare data in the following table.
	www.cs.umd.edu /users/suman/docs/731s98/node11.html (823 words)

	Dead-Code Elimination (Site not responding. Last check: 2007-10-06)
		level is 1 or higher, KAP performs dead-code elimination.
		Elimination of resolved conditionals, as shown in the following example:
		The full effect of dead-code elimination is realized when combined with other optimizations, such as subprogram inlining and forward substitution, which help in exposing useless or unreachable code.
	www.mun.ca /hpc/kapc/kapc_osf_ug0123.html (139 words)

	DeputyOptimizer - Ivy Wiki
		The first flow-insensitive pass is highly important not only because it eliminates a large number of checks, but also because it allows the flow-sensitive passes that follow to be executed efficeintly.
		The number of checks is reduced by a further 19.3% when these phases are run again after a symbolic evaluation, and an additional 16% are eliminated when duplicates unaffected by intervening statements are examined.
		From looking at the code and examining these results it seems that the biggest opportunity for improvement is in increasing the aggressiveness of Matt's analysis.
	largo.millennium.berkeley.edu /ivywiki/DeputyOptimizer (833 words)

	Java theory and practice: Dynamic compilation and performance measurement
		Only compiling code that is executed frequently has several performance advantages: No time is wasted compiling code that will execute infrequently, and the compiler can, therefore, spend more time on optimization of hot code paths because it knows that the time will be well spent.
		It can perform many of the standard optimizations found in static compilers, such as code hoisting, common subexpression elimination, loop unrolling, range check elimination, dead-code elimination, and data-flow analysis, as well as a variety of optimizations that are not practical in statically compiled languages, such as aggressive inlining of virtual method invocations.
		If the compiler is going to optimize away a block of code because it reasons the code to be irrelevant (a common situation with benchmarks that don't actually do anything), you can see it in the generated machine code -- the code is not there.
	www-106.ibm.com /developerworks/library/j-jtp12214 (3508 words)

	DeadCode - MLton Standard ML Compiler (SML Compiler) (Site not responding. Last check: 2007-10-06)
		Dead-code elimination is an optimization pass for the CoreML IntermediateLanguage, invoked from CoreMLSimplify.
		In order to compile small programs rapidly, a pass of dead code elimination is run in order to eliminate as much of the Basis Library as possible.
		The dead code elimination includes the minimal set of declarations from the Basis Library so that there are no free variables in the user program (or remaining Basis Library implementation).
	mlton.org /DeadCode (138 words)

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