Points-to and Side-effect Analyses for Programs Built with Precompiled Libraries

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Points-to and Side-effect Analyses for Programs
Built with Precompiled Libraries

• Atanas (Nasko) Rountev
• Barbara G. Ryder
• Rutgers University

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Whole-program Analysis

• Static analysis
• Optimizing compilers and SE tools
• Whole-program analysis
• Complex global properties
• Aggressive optimizations
• Helps humans
• Large body of work

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Weaknesses

• Need the whole program
• Incomplete programs
• Parts not implemented yet
• Separate compilation
• Precompiled components, no source
• Limited applicability

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Our Target Problem

• Goal handle incompleteness and separation
• Specific instance
• C programs with precompiled libraries
• Points-to analysis and side-effect analysis
• Importance
• Points-to and side-effect info is necessary
• Techniques useful for similar problems

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Overview

• Introduction
• Analysis for Programs with Libraries
• Analysis of Libraries
• Library Summary Information
• Analysis of Library Clients
• Empirical Results
• Summary

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Programs Built with Libraries

• Library module
• Write the library
• Create library binary
• Client module
• Write the client
• Compile and link with library binary
• No library source
• Need separate analyses

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Separate Analysis of a Library Module

• Unknown client modules
• Simulated by an abstract client

Abstract Client
Whole-program Analyzer
Library Solution
Library Module
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Separate Analysis of a Client Module

• Use precomputed summary information
• Enables precise analysis

Client Module
Whole-program Analyzer
Client Solution
Library Summary
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Library Summary Information

• Used later to analyze client modules
• Enclosed with library binary, reusable

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Points-to and Side-effect Analyses

• What variables may p refer to?
• Andersens analysis
• What variables may be modified?
• MOD set for each statement
• Pointer resolution p0
• Procedure calls backward propagation
• Wide range of applications

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Overview

• Introduction
• Analysis for Programs with Libraries
• Analysis of Libraries
• Library Summary Information
• Analysis of Library Clients
• Empirical Results
• Summary

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Separate Analysis of Libraries

• Unknown clients
• Access through library interface
• Abstract client
• Placeholder variable v0
• Placeholder procedure p0
• Apply whole-program analyses
• Reuse of implementation

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Abstract Client

proc p0(v1,...,vn) returns ret0 v0 vi
v0 v (v ? interface) v0 v0
v0 p0 v0 v0 v0 v0 v0
(v0)(v0,...,v0) ret0 v0

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Library Example

global g proc p1(p,fp) proc p2(r)
local s, t, q r -(r) t
p q s p2(q) t s
(fp)(t,g)
s1
MOD(s1) v0,g
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Overview

• Introduction
• Analysis for Programs with Libraries
• Analysis of Libraries
• Library Summary Information
• Analysis of Library Clients
• Empirical Results
• Summary

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Library Summary Information

• Used for separate analysis of clients
• Enclosed with library binary, reusable
• Input to whole-program analyzers
• Best possible precision
• Basic summary
• Precision-preserving optimizations
• Reduce summary size
• Reduce cost of separate analysis of clients

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Basic Summary

global g proc p1(p,fp) local s1, t, q
t p q s p2(q) t s
(fp)(t,g) proc p2(r) r -(r)
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Summary Optimizations

• Replace sets of equivalent variables
• Have the same points-to sets
• Replace with a set representative
• Remove irrelevant summary elements
• Smaller points-to and MOD sets in clients
• Inactive variables
• Inaccessible variables
• Use solution from separate library analysis

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Optimized Summary

proc p1(p,fp) ts tp (fp)(t,g) qs
proc p2(r) p2(q)
proc p1(rep1,fp) (fp)(rep1,g)
Mod(p1) (t,I) Call(p1) (p2,D) (fp,I)
Mod(p2) (r,I)
Mod(p1) (rep1,I) Call(p1) (fp,I)
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Overview

• Introduction
• Analysis for Programs with Libraries
• Analysis of Libraries
• Library Summary Information
• Analysis of Library Clients
• Empirical Results
• Summary

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Experiments

• Library and client points-to analyses
• BANE toolkit (UC Berkeley)
• Summary generation and optimization
• Publicly available C programs
• Include general-purpose libraries
• Sun Ultra-60, 360MHz, 512K memory

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Data Programs

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Cost of Library Analysis

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Cost of Client Analysis

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Cost Reduction for Client Analysis

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Summary

• Challenges for whole-program analysis
• Programs with precompiled libraries
• Points-to and side-effect analyses
• Separate analysis of libraries and clients
• Summary construction
• Future work
• Other points-to analyses
• Client analyses