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Questions tagged [ssa]

Static single assignment is a property of a compiler's intermediate representation for optimization and static analysis.

Static single assignment is an intermediate representation where each "variable" is assigned only once. When translating from a form with mutable variables, each variable is replaced with a set of variables representing each possible assignment in order to make the definition and usage of every value explicit.

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Does loop operation with variable assignment violate SSA principle?

I just started to learn LLVM IR and SSA, got a question about the SSA principle. I found the following code block on the Internet, which seems to violate SSA principle because variables are assigned value for several times. Is my comprehension…
eom
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How to build dominance frontier for control flow graph?

I would like to understand what a common principle is used for building Ф-functions for nodes. I read about "dominance frontier (DF)" relationship in a graph that allow to build Ф-functions. Here is an example with control-flow graph for simple code…
NoName
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What's the difference between effect and control edges of V8's TurboFan?

I've read many blog posts, articles, presentation and videos, even inspected V8's source code, both the bytecode generator, the sea-of-nodes graph generator and the optimization phases, and still couldn't find an answer. V8's optimizing compiler,…
Chayim Friedman
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Is my construction of SSA correct? (Renaming)

I've been learning about ssa (static single assignment form), and I was given the following graph with phi functions inserted, but the graph hasn't been renamed: I had to rename the variables, and this is what I got: I am very unsure that this is…
xilpex
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What is program point and what's the relationship with basic block?

When I read the book "Compilers: Principles, Techniques, and Tools", I always meet the word "program point", though I got a blur feeling about what it is, and with this feeling, I went through the chapter about data flow analysis, I still want to…
user2269707
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How to get program variable which a phi variables contains in LLVM-IR

for a IR like %.0 = phi i32* [ @y, %bb2 ], [ @z, %bb3 ] %.1 = phi i32* [ %.0, %bb4 ], [ %.x, %bb19 ] store i32* %.1, i32** @x, align 8 So if I am iterating in my llvm-pass and encounter use of 0.1 at third instruction. I store it in value class…
Akshay Gupta
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What programming language is displayed?

Since I couldn't find anything on Google and I have never seen such syntax before t11 = phi [0: 2:int, 1: t10] #i t12 = t11 < 70:int if t12 goto 1 else 2 t2 = t11 / 2:int t3 = &pow10tab[t11] t4 = &pow10tab[t2] t5 = *t4 t6 = t11 - t2 I like to ask…
Eden Shvartz
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Dimensionality reduction using (multivariat) Singular Spectrum Analysis

I have given a time-series in various channels. There are two major oscillations "hidden" in the time-series and distributed over all channels. I want to extract these oscillations using multivariate Singular Spectrum (mSSA) Analysis. I am new to…
refle
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benchmarks for register allocation in SSA-form

i want to do graph coloring on chordal graphs. i need some chordal graphs and their results to compare my work against theme. can anyone help me? for example 164.gzip 175.vpr 176.gcc 181.mcf 186.crafty 197.parser …
shabnam_mrz
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LLVM IR position of predecessor block labels in phi node instruction

When using a phi node in a basic block is there a suggested order in which I should place the labels if there is a higher probability that the predecessor is a certain block. For example take the simple factorial function listed below. define…
Daniel Robertson
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Semantics of SSA and multiple assignment

In SSA form, a variable assigned from a phi ends up with the appropriate value depending on which path it was reached by. But what happens if, perhaps via some unusual path, both inputs to the phi have been assigned? e.g. a = 1 ... b = 2 ... c =…
rwallace
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Converting stack pushing loop to three address code basic block

I've been working on a small compiler (Using llvm, but shoulden't matter) for a super simple stack based language. I've been reading a lot of papers about translating an evaluation stack based language to TAC or SSA, and the basic procedure outlined…
Miguel Ángel
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How to accumulate results with SSA in Erlang?

This is a total functional newbie question. I'm trying to learn some Erlang and have created a (hopefully concurrent) Monte Carlo Simulation where multiple processes are spawned, which report their local results to the parent process via message…
user1101674
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How to deal with variables cannot be converted to SSA form?

I remember reading this somewhere that not all variables can be converted to SSA form. For example, aliased variables and probably pointers and global variables are not candidates for SSA. Aggregate and array variables may be tricky. If a real…
wildpi
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Do PHI nodes remain in LLVM IR until compilation to binary?

I am new to LLVM and Intermediate Representation (IR), and I am trying to understand how PHI nodes are handled in LLVM IR. I understand that PHI nodes are a fundamental component of SSA (Static Single Assignment) form in LLVM IR, and are used to…
Volodya Lombrozo
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