LLVM: A Compila ilation Framework for Lifelong Progr for Lifelong - - PowerPoint PPT Presentation

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LLVM: A Compila ilation Framework for Lifelong Progr for Lifelong - - PowerPoint PPT Presentation

Nov 22, 2022 353 likes •576 views

Systems and Internet Infrastructure Security ity Network and Security Research Center Department of Computer Science and Engineering Pennsylvania State University, University Park PA LLVM: A Compila ilation Framework for Lifelong Progr for

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SLIDE 1

Systems and Internet Infrastructure Security

Network and Security Research Center Department of Computer Science and Engineering Pennsylvania State University, University Park PA

LLVM: A Compila for Lifelong Progr

Systems and Internet Infrastructure Security (SIIS) Laboratory

for Lifelong Progr Transfor

Chris Lattner an Presented by: N

ity

ilation Framework gram Analysis and

Page 1

gram Analysis and

  • rmation

and Vikram Adve Nirupama Talele

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Agenda

  • What is LLVM
  • LLVM Code Represent
  • LLVM Compiler Archite

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Framework Analysis

ntation itecture

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LLVM

  • “Compiler framework desig

lifelong, program analysis

  • Provides high level info to

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Compile-time
  • Link-time
  • Run-time
  • In-idle-time

signed to support transparent, is and transformation” to compiler transformations

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LLVM

  • Program analysis shou

lifetime of a program

  • Intra-procedural optimiz

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Intra-procedural optimiz
  • Machine-dependent opt
  • Dynamic optimization (r
  • Profile-guided optimizat

uld occur through the

izations (link time)

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izations (link time) ptimizations (install time) (run time) ations (idle time)

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LLVM Difference

  • No high-level construct
  • classes, inheritance, etc

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • No runtime system or o
  • Does not guarantee sa
  • type and memory

e with VMs

cts

etc

Page

r object model afety

5

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LLVM Analysis

  • Aim to make lifelong an

programmers

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Achieved through two p
  • Code Representation
  • Compiler Architecture

analysis transparent to

Page

parts:

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LLVM Code Repr

  • Key feature: high and low
  • RISC-like instruction set
  • SSA-based representation

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • SSA-based representation
  • Low-level, language indep
  • LLVM is complementary to

JVM,Microsoft CLI), not an

presentation

w level

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ependent type system to virtual machines(like an alternative

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LLVM Code Repr

  • How Support Lifelong A
  • 5 capabilities
  • Persistent program info
  • Offline code generation

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Offline code generation
  • User-based profiling/op
  • Transparent runtime mo
  • Uniform, whole program
  • No previous system pro

presentation

Analysis?

formation n

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n ptimization

  • del

m compilation

rovides all 5

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Instruction Set

  • Avoids machine specific co
  • Infinite set of typed virtual
  • In SSA form
  • Includes support for phi fun
  • This allows flow insensitive

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • This allows flow insensitive

sensitive without expensive

  • Avoids same code for mul
  • pcodes)
  • Is in load/store form -progr

registers and memory sole

  • perations using typed po

constraints al registers

nctions ve algo to gain benefits of flow

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ve algo to gain benefits of flow ve Data Flow analysis

ultiple instructions (overloaded grams transfer values between lely via load and store

  • inters

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Type Information

  • Makes all address arith

to all LLVM optimizatio

Example :- X[i].a = 1; (assuming a is third field)

Systems and Internet Infrastructure Security (SIIS) Laboratory

Example :- X[i].a = 1; (assuming a is third field) %p = getelementptr %xty* %X, long %i, ubyte 3; store int 1, int* %p;

  • All addressable objects

allocated ithmetic explicit, exposing it ions.

X[i].a = 1; (assuming a is third field)

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X[i].a = 1; (assuming a is third field) %p = getelementptr %xty* %X, long %i, ubyte 3;

ts (“lvalues”) are explicitly

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Exception Hand

  • Exceptions mechanism

instructions

  • invoke
  • unwind

Systems and Internet Infrastructure Security (SIIS) Laboratory

unwind

  • Isolate code to throw/re

front-end libraries

  • Handling automatic var
  • An invoke instruction is

destructor is run, then u the unwind instruction.

dling

m based on two

Page

/recover from exceptions to ariable destructors:

is used to halt unwinding, the unwinding is continued with

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LLVM Compiler A

  • Remember: goal to ena

link-time, install-time, ru

  • Must be transparent to

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Must be transparent to

and end-users

  • Efficient enough for use

applications

Architecture

nable transformations at run-time, and idle-time to application developers

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to application developers se with real-world

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LLVM Compiler A

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • This strategy provides the
  • Some limitations
  • Language specific optimiza

end

  • Benefit to languages like Ja

systems?

Architecture

Page

e 5 benefits discussed earlier

ations must be performed on front Java requiring sophisticated runtime

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LLVM Compiler A

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Front-end compiler
  • Translate source code to LL
  • Perform language specific o
  • Need not perform SSA const
  • Invoke LLVM passes for glo

at module level

Architecture

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LLVM representation c optimizations nstruction at this time lobal inter procedural optimization

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LLVM Compiler A

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Linker/Interprocedure Opti
  • Various analyses occur
  • Points-to analysis
  • Mod/Ref analysis
  • Dead global elimination, dead

propagation, array bounds che

  • Can be speeded up by adding

Architecture

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ptimizer

d argument elimination, constant heck, etc g inter-procedural summaries)

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LLVM Compiler A

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Native Code Generation
  • JIT or Offline
  • Currently supports Sparc V

Architecture

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c V9 and x86 architectures

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LLVM Compiler A

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Reoptimizers
  • Identifies frequently run cod
  • Performs additional optimiza

generation can be performe

  • Idle-time reoptimizer

Architecture

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code and ‘hotspots’ izations, thus native code ed ahead of time

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LLVM Analysis

  • When compiled to LLV

undergo the following a

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Flow-insensitive, field-s

points-to analysis

  • Uses Data Structure An

VM, a program can analyses

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sensitive, context-sensitive nalysis (DSA)

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LLVM Analysis –

  • Relatively compact cod

Systems and Internet Infrastructure Security (SIIS) Laboratory

Code Size

  • de size

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Conclusion

  • LLVM is language inde
  • Optimizations at all sta

(compile,link, runtime, e

  • Compact code size

Systems and Internet Infrastructure Security (SIIS) Laboratory

  • Efficient- due to small,

low level representation

  • Future work: can high-l

implemented on top of

  • ptimization and code g

ependent tages of software lifetime , etc)

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ll, uniform instruction set in ion level VMs be f the LLVM runtime e generation framework?

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Questions?

Systems and Internet Infrastructure Security (SIIS) Laboratory Page 21