1. Atanas (Nasko) Rountev Barbara G. Ryder Rutgers University
Points-to and Side-effect Analyses for Programs Built with Precompiled Libraries
Atanas (Nasko) Rountev
Barbara G. Ryder
Rutgers University
April 2, 2001
CC 2001

2. Whole-program Analysis
Static analysis
Optimizing compilers and SE tools
Whole-program analysis
Complex “global” properties
Aggressive optimizations
Helps humans
Large body of work
April 2, 2001
CC 2001

3. Weaknesses Need the whole program Incomplete programs
Parts not implemented yet
Separate compilation
Precompiled components, no source
Limited applicability
April 2, 2001
CC 2001

4. 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
April 2, 2001
CC 2001

5. Overview Introduction Analysis for Programs with Libraries
Analysis of Libraries
Library Summary Information
Analysis of Library Clients
Empirical Results
Summary
April 2, 2001
CC 2001

6. 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
April 2, 2001
CC 2001

7. Separate Analysis of a Library Module
Unknown client modules
Simulated by an abstract client
Abstract
Client
Whole-program
Analyzer
Library
Solution
Library
Module
April 2, 2001
CC 2001

8. Separate Analysis of a Client Module
Use precomputed summary information
Enables precise analysis
Client
Module
Whole-program
Analyzer
Client
Solution
Library
Summary
April 2, 2001
CC 2001

9. Library Summary Information
Used later to analyze client modules
Enclosed with library binary, reusable
Abstract
Client
Library
Module
Whole-program
Analyzer
Solution
Summary
Generator
Library
April 2, 2001
CC 2001

10. Points-to and Side-effect Analyses
What variables may *p refer to?
Andersen’s analysis
What variables may be modified?
MOD set for each statement
Pointer resolution: *p=0
Procedure calls: backward propagation
Wide range of applications
April 2, 2001
CC 2001

11. Overview Introduction Analysis for Programs with Libraries
Analysis of Libraries
Library Summary Information
Analysis of Library Clients
Empirical Results
Summary
April 2, 2001
CC 2001

12. 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
April 2, 2001
CC 2001

13. 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; }
April 2, 2001
CC 2001

14. 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); } fp p0 p1 t p g v0
s1:
MOD(s1) = {v0,g}
April 2, 2001
CC 2001

15. Overview Introduction Analysis for Programs with Libraries
Analysis of Libraries
Library Summary Information
Analysis of Library Clients
Empirical Results
Summary
April 2, 2001
CC 2001

16. 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
April 2, 2001
CC 2001

17. Basic Summary proc p1(p,fp) *t=s t=p (*fp)(t,g) q=&s proc p2(r) p2(q)
global g;
proc p1(p,fp) {
local s=1, t, q;
t = p;
q = &s;
p2(q);
*t = s;
(*fp)(t,g); }
proc p2(r)
{ *r = -(*r); }
proc p1(p,fp) *t=s
t=p (*fp)(t,g)
q=&s proc p2(r)
p2(q)
Mod(p1): (t,I)
Call(p1) : (p2,D) (fp,I)
Mod(p2): (r,I)
April 2, 2001
CC 2001

18. 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
April 2, 2001
CC 2001

19. Optimized Summary proc p1(p,fp) *t=s t=p (*fp)(t,g) q=&s 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)
April 2, 2001
CC 2001

20. Overview Introduction Analysis for Programs with Libraries
Analysis of Libraries
Library Summary Information
Analysis of Library Clients
Empirical Results
Summary
April 2, 2001
CC 2001

21. 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
April 2, 2001
CC 2001

22. Data Programs
April 2, 2001
CC 2001

23. Cost of Library Analysis
April 2, 2001
CC 2001

24. Cost of Client Analysis
April 2, 2001
CC 2001

25. Cost Reduction for Client Analysis
April 2, 2001
CC 2001

26. 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
April 2, 2001
CC 2001