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Questions tagged [data-flow-analysis]

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Basic Blocks: Interrupted by "pointless" goto?

So I was studying some about compiler optimizations and as part of that, Control Flow Graphs (CFG's). Specifically, I saw a "basic block" being defined as "a straight-line code sequence ...
AnonA's user avatar
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Collapsing loops in a control-flow graph

Let's say we are given some CFG, maybe in SSA-form, and we want to "collapse" each top-level loop into s single node, whose successors would be all exit blocks of the original loop. So we ...
return true's user avatar
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data flow analysis reaching definition analysis meaning

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 ...
Jorayen's user avatar
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3 votes
1 answer
113 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 ...
David Yue's user avatar
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1 answer
206 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 ...
user3779002's user avatar
2 votes
0 answers
43 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 ...
James Bowery's user avatar
4 votes
1 answer
120 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 ...
Abhishek Ghosh's user avatar
1 vote
1 answer
38 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 ...
The Pointer's user avatar
1 vote
1 answer
67 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 ...
The Pointer's user avatar
4 votes
1 answer
98 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 ...
mythbuster's user avatar
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1 answer
336 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 ...
macro_controller's user avatar
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194 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 ...
user2994783's user avatar
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0 answers
59 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, ...
securitymensch's user avatar
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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 ...
user1999109's user avatar
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?
TheAhmad's user avatar
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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 ...
lilott8's user avatar
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0 votes
1 answer
319 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(...
Lance's user avatar
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0 votes
1 answer
337 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 ...
Lance's user avatar
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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,...
Lance's user avatar
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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 ...
mdxg's user avatar
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2 votes
1 answer
615 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 ...
dsax7's user avatar
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0 votes
1 answer
46 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 ...
dsax7's user avatar
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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 ...
Gaslight Deceive Subvert's user avatar
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: ...
Gaelan's user avatar
  • 123
2 votes
1 answer
55 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, ...
lllllllllllll's user avatar
2 votes
1 answer
663 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 ...
Sridhar Sarnobat's user avatar
6 votes
1 answer
223 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 ...
Yaroslav Bulatov's user avatar
2 votes
1 answer
94 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 ...
user1868607's user avatar
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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 ...
zr.'s user avatar
  • 171
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 <...
El Marce's user avatar
  • 333
3 votes
3 answers
623 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 $L$ "...
user avatar
1 vote
1 answer
128 views

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, ...
Haych's user avatar
  • 534
4 votes
1 answer
3k views

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 ...
Haych's user avatar
  • 534
6 votes
1 answer
2k views

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 ...
Eli Bendersky's user avatar
6 votes
1 answer
2k views

Difference between "data dependence graph", "data dependency graph", and "data flow graph"

Is there a difference between a "data dependence graph" and a "data dependency graph"? I have seen both terms - sometimes used interchangeably sometimes not. To make things even more complicated, a "...
langlauf.io's user avatar
4 votes
1 answer
6k views

What are GEN and KILL statements in dataflow analysis?

In data flow analysis, is GEN statement where a variable is used and KILL statement is where variable is redefined?
kaitlynrutledge's user avatar