# Questions tagged [data-flow-analysis]

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I'm trying to understand reaching definitions and I'm having hard problem wrapping it around my head with the following definition (taken from the the following paper page 114): $B_i\;\text{be a ... 1 vote 1 answer 61 views ### Dataflow Analysis: Available Expressions, why is OUT[B] initialized to universal set? In the dragon book, section 9.2.6, why is the$OUT[B]$initialized to$U$except for$OUT[ENTRY]$. Wouldn't using the$OUT[B] = \emptyset \quad \forall B$be a more conservative solution? The book ... 0 votes 1 answer 145 views ### What is the intepretation of the top & bottom elements of a lattice? (moved from stackoverflow to here) I'm trying to understand dataflow stuff for program analysis. Transfer functions move lattice elements up (towards top ⊤) and down (towards bottom ⊥). Sometimes the ... 2 votes 0 answers 42 views ### Is there a functional programming language with inherent change propagation? Change propagation in programming environments is an add-on at the framework level such as React. There was a lot of work on dataflow virtual machines in the wake of Backus's Turing Award Lecture on ... 4 votes 1 answer 114 views ### Can reading a value of a variable kill the definition of the variable? I was going through the concept of reaching definitions from the red dragon book. The authors define reaching definitions as follows: Definition: We say a definition$d$reaches a point$p$if there ... 1 vote 1 answer 36 views ### How do we know that$F^{n + 1}(\overrightarrow{\emptyset}) = F(F^n(\overrightarrow{\emptyset}))$? I am currently studying the textbook Principles of Program Analysis by Flemming Nielson, Hanne R. Nielson, and Chris Hankin. Chapter 1.3 Data Flow Analysis says the following: The least solution. The ... 1 vote 1 answer 61 views ### Showing that$F$is a monotone function I am currently studying the textbook Principles of Program Analysis by Flemming Nielson, Hanne R. Nielson, and Chris Hankin. Chapter 1.3 Data Flow Analysis says the following: The least solution. The ... 4 votes 1 answer 94 views ### Which language is used to construct a type system? Typically, OCaml and Scala seem to be used for designing any programming languages tool. But what features offer them an edge over other languages. A related question, is a type system for a language ... 0 votes 1 answer 274 views ### Difference between forward/backward slicing and reaching definition - def/use - use/def chains I'm a little bit confused about the difference between forward/backward slicing and the use/def-def/use as part of the reaching definitions technique. Isn't the use-def chain supposed to be equivalent ... 0 votes 0 answers 148 views ### Difference between data flow and control flow I am trying to read a paper. I can’t understand the difference between data flow and control. Maybe control flow means OS's or hardware's steps taken for execution of statements whereas data flow ... 0 votes 0 answers 54 views ### Compiler design: How are the initialize conditions for data-flow problems set? Consider a typical data-flow problem, for example, reaching definitions or available expressions. I am struggling to understand how$IN$and$OUT$of the basic blocks are initialized. For example, ... 0 votes 0 answers 1k views ### How to draw flowchart for if condition within nested loops? Please find my program logic as below : Please find my flowchart for the above program logic as below: My superior asked me correct the flowchart. But I couldn't identify my mistakes. Please guide ... 1 vote 0 answers 58 views ### Order of Traversal in Bidirectional Dataflow Analysis Does order of traversing CFG matter in solving bidirectional dataflow problems, from a performance perspective? 2 votes 2 answers 74 views ### When to use Context-(in)Sensitive Inter-procedural Data Flow Analysis I've been exploring the differences between Context Sensitive Analysis (CSA) and Context Insensitive Analysis (CIA), members of ... 0 votes 1 answer 307 views ### How to Compute the Fixed Point on a DataFlow Lattice Wondering the general overview of how to compute the fixed point on a program's dataflow lattice. A fixed point of a function$f(x)$is one where the output of the function equals the input, so:$$f(... 0 votes 1 answer 316 views ### How to Construct a Lattice from Program Statements In order to optimize a program, I am trying to figure out how the idea of a lattice applies to data-flow graphs, as introduced by this presentation (first diagram below). The lattice seems to take a ... 1 vote 1 answer 2k views ### Why use a CFG instead of a DFG I just realized a Control-Flow Graph (CFG) is composed of basic blocks, which is a set of instructions. It is mentioned that you can still do stuff like dead code elimination and whatnot, with the CFG,... 2 votes 0 answers 1k views ### Calculation of Gen and Kill set for data flow analys I'm currently preparing for an exam in compiler construction. The course is mainly about optimization in the backend of the compiler. For the optimization we have to do data flow analysis by hand. In ... 2 votes 1 answer 560 views ### Why is it better to do the data flow analysis in the basic blocks I have been reading about compilers and it is said that doing the data flow analysis in the basic blocks is more optimal. Sadly, quoting the exact source, would be slightly hard as it is not in ... 0 votes 1 answer 44 views ### Saving information from reaching definition I am learning about compilers at the moment and in my textbook it is briefly mentioned that UD/DU (Use-Def, Def-Use Chains) a way of saving information from the reaching definition is. It is just said ... 2 votes 0 answers 176 views ### Novel escape analysis algorithm for Java Today I read a very interesting article about escape analysis in Java called Escape Analysis for Object Oriented Languages: Application to Java I think I have some grasp on how escape analysis works ... 2 votes 2 answers 38 views ### Inferring used fields in return type A common issue in app development is avoiding over-fetching of data, such as in this naive (pseudocode) example: ... 2 votes 1 answer 54 views ### Cut costly functions in inter-procedural abstract interpretation I am performing some inter-procedural abstract interpretation to capture certain program properties. Following the standard way, what I am doing is to maintain a work list of to-be-analyzed functions, ... 2 votes 1 answer 609 views ### What makes data flow analysis higher level than control flow analysis? I feel understanding why data flow is higher level than control flow is key to writing good code (and convincing others during code reviews). I find this repeatedly when arguing why my functional ... 6 votes 1 answer 210 views ### Memory needed for computational graph Suppose we have a set of equations like this p7=f(p1+p6); p6=f(p2+p5); p5=f(p3+p4); p4=f(p3); p3=f(p2); p2=f(p1); p1=f() It can be represented by computational ... 2 votes 1 answer 93 views ### Data-flow analysis problem adjust to Ullman-Aho's framework? I am reading the classical book "Compilers. Principles, techniques and tools" by Aho et alii. On chapter 9.3 they talk about a general framework to solve data-flow analysis problems that use a ... 7 votes 1 answer 1k views ### When is it useful to split critical edges? Some compilers have utility functions that split critical edges in the control flow graph. I assume that this is not done as an optimization in itself, but rather to simplify other analyses and ... 2 votes 1 answer 64 views ### Data flow equations to determine value dependencies I need to define the data-flow analysis equations to determine the value dependencies of an statement. For example: a = 9 b = a + 7 c = b * 2 the value of <... 3 votes 3 answers 620 views ### Formal notion of a call graph for Turing machines To most computer programs one can assign a "call graph". Is there a formal notion of call graphs of Turing machines? Motivation is, that one could intuitively call a decidable language$L\$ "... 1 vote
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### If Data-Flow Analysis is able to approximate, what does that mean?

I have been learning about data-flow analysis and have come across the idea of approximations and that the data-flow analysis should be able to under and over approximate a situation. For example, ...
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### Backward vs Forward Data-flow Analysis

I understand how both forward and backward data-flow analysis work but in what situations would we use them? Why do we need to be able to do it in both ways? Do compilers of certain types perform one ...
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### Backward data-flow: post-order or RPO on reverse CFG?

When solving backward data-flow problems, many resources (Wikipedia and many presentations found online) recommend traversing the control-flow graph (CFG) in post-order for fastest convergence, which ...