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# Topic: Constant propagation

 Constant folding - Wikipedia, the free encyclopedia A more advanced form of constant propagation known as sparse conditional constant propagation may be utilized to simultaneously remove dead code and more accurately propagate constants. Constant folding can be done in a compiler's front end on the IR tree that represents the high-level source language, before it is translated into three-address code, or in the back end, as an adjunct to constant propagation. Constant propagation can also cause conditional branches to simplify to one or more unconditional statements, when the conditional expression can be evaluated to true or false at compile time to determine the only possible outcome. en.wikipedia.org /wiki/Constant_propagation   (607 words)

 Brown CS: Tech Report CS-91-22 Constant propagation is a well-known global flow analysis problem. The goal of constant propagation is to discover values that are constant on all possible executions of a program and to propagate these constant values as far forward through the program as possible. A new algorithm is also presented that performs a form of interprocedural data flow analysis in which aliasing information is gathered in conjunction with constant propagation. www.cs.brown.edu /publications/techreports/reports/CS-91-22.html   (158 words)

 [No title] In general, to replace a use of "x" by a constant "k", we have to know that: (*) On every path leading to the use of "x", the last assignment to "x" is "x := k". The "global constant propagation" problem is a paradigmatic example of many similar global optimizations. Liveness is actually simpler than constant propagation, since it is a simple boolean property (either true or false). www.cs.berkeley.edu /~aiken/cs264/lectures/dataflow164   (1903 words)

 Conditional Pointer Aliasing and Constant Propagation   (Site not responding. Last check: 2007-10-08) A natural way to tackle this mutual dependence between conditional constant propagation and pointer analysis is to iterate over the two analyses until a fixed point is reached. Though this is unappealing because of efficiency concerns, the resulting precision may also not be optimal, i.e., a more tightly-coupled analysis may have better precision for both alias analysis and conditional constant propagation than iterating over the two analyses. I will describe the system used and the experiments performed that study the effects of combining several different pointer alias analyses and conditional constant propagation in a simple iterating-over-analyses fashion and a combined version where the analyses are more closely coupled. www.mcs.newpaltz.edu /colq/pioli.html   (239 words)

 Constant propagation delay current reference - Patent 4862015 The frequency of operation for the ring oscillator is dependent solely on the propagation delay of the inverters, and the propagation delay of the inverters are controlled by varying this injector current. Additional adjustment of output currents I.sub.2 -I.sub.N, and consequently circuit propagation delays, can be provided by multiplying the emitter areas of transistors 30-34 relative to the emitter area of diode connected transistor 18, as is well known to one of ordinary skill in the art. Because constant propagation delay characteristics can be obtained, as described, problems such as race conditions which ordinarily only show up over temperature or operating voltage excursions are eliminated in the logic circuit. www.freepatentsonline.com /4862015.html   (2472 words)

 Constant Propogation   (Site not responding. Last check: 2007-10-08) Constant propagation is the replacement of expressions, usually variables, with a constant value that the compiler determines it will have at compile-time. This can result in better instruction selection where you can use "immediate" machine code instructions which embed constants in the instruction, and result in faster execution than if a register must be used to store the constant. This removes the need for using a preprocessor for constants, as is standard practice in C. Constant propagation can result from learning more about the values of variables throughout the program. users.chariot.net.au /~matty/ultra/optcat/Constant_Propagation.html   (157 words)

 Parallel plate waveguide   (Site not responding. Last check: 2007-10-08) This mode has a normalized propagation constant that is always equal to one, provided that the material between the plates is free space. The normalized propagation constant of all higher order modes is between zero and one when you have free space between the plates. The upper limit of this interval is the normalized propagation constant of the primary mode. www.ifh.ee.ethz.ch /~hafner/1MaXTut/Parallelplatewaveguide.htm   (1707 words)

 Constant Propagation: A Fresh, Demand-Driven Look - Stoltz, Wolfe, Gerlek (ResearchIndex)   (Site not responding. Last check: 2007-10-08) Abstract: Constant propagation is a well-known static compiler technique in which values of variables which are determined to be constants can be passed to expressions which use these constants. Code size reduction, bounds propagation, and dead-code elimination are some of the optimizations which benefit from this analysis. 32 Interprocedural constant propagation: A study of jump functi.. citeseer.ist.psu.edu /stoltz94constant.html   (445 words)

 Ghinsu CR: Constant propagation   (Site not responding. Last check: 2007-10-08) Constant propagation is a code reduction technique that replaces program variables with constant values. The application of constant propagation in the example presented above may appear obvious and the example itself may seem oversimplified. It is true that no real-world source program would be like this, because a good programmer would have taken into account the constant value of the variable and would have propagated it in the first place. www.softlab.ntua.gr /research/research_projects/Ghinsu/ghincr31.html   (256 words)

 Beyond Constant Propagation Constant propagation is one of the best explored program optimization techniques. This propagation is executed by a worklist-based fixpoint algorithm that additionally applies rules at every iteration. Propagation of relational expressions is done there in the context of partial evaluation as a program transformation methodology used on programs after collecting dataflow information. sakharov.net /propagation.html   (250 words)

 Technical Program Paper Detail - AIChE   (Site not responding. Last check: 2007-10-08) The predicted apparent propagation rate constant remains truly constant at low conversions, but it then starts to drop by orders of magnitude as free radicals encounter obstacles in accessing functional groups (as quantified by the actual average number of functional groups neighboring each radical). However, this favored propagation does not last to high conversions when the initiation rate constant is raised because the initiators are consumed faster. raising the initiation rate constant or the primary cyclization rate constant, shorten the kinetic chain length, and lower the conversion when initiators are exhausted. www.aiche.org /conferences/techprogram/paperdetail.asp?PaperID=1671&DSN=annual01   (387 words)

 Propagating Constants Past Software to Hardware Peripherals   (Site not responding. Last check: 2007-10-08) While constant propagation in synthesis tools is commonly done, this work illustrates the benefits of recognizing initialization constants from the software as really being constants for hardware. Now, suppose we could somehow propagate the constant "10" into the VHDL description of the core, before the core were synthesized, letting the synthesis tool know that cont_reg would be written by that constant and only that constant. If the only access to that register is a write with a constant, and this write occurs during the reset or boot routines, as is often the case in embedded systems, then we have a candidate for constant propagation to peripheral cores. www.cs.ucr.edu /~vahid/pubs/colp01_cp_html   (3677 words)

 SUNY New Paltz Department of Computer Science   (Site not responding. Last check: 2007-10-08) Conditional constant propagation can, in turn, discover unexecutable code, which can improve the precision of pointer analysis. One way to resolved this mutual dependence between conditional constant propagation and pointer alias analysis is to iterate over the two analyses until a fixed point is reached. In this work we explore three combinations of pointer alias analysis and conditional constant propagation: a one-pass-over-analyses approach, an iterate-over-analyses approach, and a new algorithm that synthesizes pointer alias analysis and conditional constant propagation. www.newpaltz.edu /compsci/technicalreports/99-103.html   (193 words)

 10.1.3 Local Common Subexpression Elimination   (Site not responding. Last check: 2007-10-08) Constants are produced, not only by the programmer, but also by the compiler. The programmer may initialize a variable to be 1, using this as both the loop counter and as an array index. A related optimization computes constant expressions at compile-time rather than generating code to perform the optimization. www.cs.wpi.edu /~kal/PLT/PLT10.1.3.html   (126 words)

 Melles Griot Optics Guide - The Propagation Constant The propagation of a pure Gaussian beam can be fully specified by either its beam waist diameter or its far-field divergence. The need for a figure of merit for laser beams that can be used to determine the propagation characteristics of the beam has long been recognized. The concept of a dimensionless beam propagation parameter was developed in the early 1970s to meet this need, based on the fact that, for any given laser beam (even those not operating in the TEM www.mellesgriot.com /products/optics/gb_3_2.htm   (422 words)

 Examples In addition to inlining, our optimization enables constant propagation by providing opportunities for both interprocedural and intraprocedural constant propagation. (In general, knowing a type allows the number of cases to be pruned.) In the resulting code, shown Figure 4c, our optimization, inlining, and constant propagation have combined to transform a dynamic call into a static call. Constant propagation of this value allows the nested switch statements to be flattened; after inlining the calls on www.ebb.org /bkuhn/writings/technical/cpp-opt/node5.html   (340 words)

 Definition: attenuation constant   (Site not responding. Last check: 2007-10-08) The real part of the propagation constant in any electromagnetic propagation medium. Note 1: The attenuation constant is usually expressed as a numerical value per unit length. For a particular propagation mode in an optical fiber, the real part of the axial propagation constant. www.its.bldrdoc.gov /projects/devglossary/_attenuation_constant.html   (75 words)

 Constant Propagation   (Site not responding. Last check: 2007-10-08) Constants assigned to a variable can be propagated through the flow graph and substituted at the use of the variable. Below is the code fragment after constant propagation and constant folding. Some compilers perform constant propagation within basic blocks; some compilers perform constant propagation in more complex control flow. www.nullstone.com /htmls/category/consprop.htm   (105 words)

 Flow-Sensitive Interprocedural Constant Propagation   (Site not responding. Last check: 2007-10-08) We present a flow-sensitive interprocedural constant propagation algorithm, which supports recursion while only performing one flow-sensitive analysis of each procedure. We present experimental results which show that this method finds substantially more constants than previous methods and is efficient in practice. We introduce new metrics for evaluating interprocedural constant propagation algorithms which measure the number of interprocedural constant values that are propagated. www.research.ibm.com /people/h/hind/pldi95abs.html   (74 words)

 Citations: Constant propagation: A fresh demand-driven look - Stoltz, Wolfe, Gerlek (ResearchIndex)   (Site not responding. Last check: 2007-10-08) The most used algorithm for constant propagation is the Sparse conditional constant propagation (SCC) 21,17,14,2] SCC is an optimistic algorithm which avoids to consider.... SCC is an optimistic algorithm which avoids to consider unreachable code and continues the propagation of constant values in the branches of conditionals statements. ERROR ANALYSIS Though the value range propagation algorithm in the previous section can determine the minimum number of bits required for the integer part of the real variable, this is not true for the fractional part of the real variable. citeseer.ist.psu.edu /context/680019/187410   (585 words)

 [No title]   (Site not responding. Last check: 2007-10-08) Constant propagation (CP) is a powerful, practically rele vant optimization of sequential programs. In fact, because of the computational complexity introduced by the state explosion problem, the successful transfer of sequential techniques to the parallel setting is currently re stricted to bitvectorbased optimizations, which because of their struc tural simplicity can be enhanced to parallel programs at almost no costs on the implementation and computation side. Enhancing the framework for efficient bitvector analyses of parallel programs of [13, 15], we develop a powerful algorithm for parallel constant propagation (PCP), which can be implemented as easily and as efficiently as its sequential counterpart for simple constants, which are computed by stateoftheart sequential optimizers. www.europar98.ecs.soton.ac.uk /WebPages2/abstracts/305_abs.html   (124 words)

 [No title]   (Site not responding. Last check: 2007-10-08) This assignment asks you to design and implement a constant propagation algorithm for an imaginary intermediate representation for a Java-like imperative language. First, determining when it would be ok to replace a variable reference by a propagated constant, and second, actually enacting the transformation. Write a function that filters the statements in which a variable's definition dominates its use and the variable's value is a known constant. www.cs.berkeley.edu /~abegel/cs302/ps4.txt   (1112 words)

 Constant Propagation Encyclopedia Article, Definition, History, Biography   (Site not responding. Last check: 2007-10-08) Looking For constant propagation - Find constant propagation and more at Lycos Search. Find constant propagation - Your relevant result is a click away! Look for constant propagation - Find constant propagation at one of the best sites the Internet has to offer! www.karr.net /search/encyclopedia/Constant_propagation   (775 words)

 Definition: propagation constant   (Site not responding. Last check: 2007-10-08) For an electromagnetic field mode varying sinusoidally with time at a given frequency, the logarithmic rate of change, with respect to distance in a given direction, of the complex amplitude of any field component. , the imaginary part, is the phase constant. In a physical transmission medium, e.g., a coaxial cable or optical fiber, the velocity of an electrical or electromagnetic signal expressed as a decimal fraction of the speed of light in vacuuo. www.atis.org /tg2k/_propagation_constant.html   (120 words)

 Passes Constant folding and some arithmetic simplifications are also done during this pass, on the tree representation. This pass is more aggressive than the constant propgation done by the CSE and GCSE pases, but operates in linear time. If constant propagation causes conditional jumps to become unconditional or to become no-ops, jump optimization is run again when CSE is finished. www.fnal.gov /docs/products/gcc/v3_1/gccint.info,.Passes.html   (3228 words)

 : Package EDU.purdue.cs.bloat.trans Performs copy and constant propagation on the blocks in a control flow graph. A value folder is then used to eliminate redundent nodes from and to propagate constants through the control flow graph. Constant propagation removes unnecessary assignments by replacing variables that are assigned constant values with those values. www.cs.purdue.edu /s3/projects/bloat/docs/api/EDU/purdue/cs/bloat/trans/package-summary.html   (488 words)

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