IBM Research

© 2006 IBM Corporation

CDT Static Analysis Features

CDT Developer Summit - Ottawa

Beth Tibbitts tibbitts@us.ibm.comSeptember 20, 2006

This work has been supported in part by the Defense Advanced Research Projects Agency (DARPA) under contract No. NBCH30390004.

IBM Research

© 2006 IBM Corporation

2

The Problem

Static Analysis of C programs is useful

Existing Abstract Syntax Tree (AST) in Eclipse CDT provides basic navigation and information, but needs more

IBM Research

© 2006 IBM Corporation

3

CDT AST Extensions

Enhance existing CASTNode and Visitor – bottom-up traversal

Add other additional graphs:– Call Graph– Control Flow Graph– Data Dependence Graph

Traversal of these new graphs available in:– Topological Order– Reverse Topological Order

IBM Research

© 2006 IBM Corporation

4

Bottom-up AST traversal

org.eclipse.cdt.core.dom.ast.ASTVisitor

org.eclipse.cdt.core.dom.ast.c.CASTVisitor

Existing:

public int visit(IASTxxx..){

return PROCESS_CONTINUE;

}

New:

public int leave(IASTxxx..){

return PROCESS_CONTINUE;

}

IBM Research

© 2006 IBM Corporation

5

Call Graph

main

a

kei

gee

foo

Recursive calls detected…

A cycle is detected on foo, gee and kei

#include "mpi.h"#include "stdio.h" void foo(int x);void gee(int x);void kei(int x);

void foo(int x){ x ++; gee(x);}

void gee(int x){ x *= 3; kei(x);}

void kei(int x){ x = x % 10; foo(x);}

void a(int x){ x --;}

int main3(int argc, char* argv[]){ int x = 0; foo(x); a(x);}

IBM Research

© 2006 IBM Corporation

6

Control Flow Graph & Data Flow Dependence Graph– sample program

#include <stdio.h>

#include <string.h>

#include "mpi.h"

// Sample MPI program

int main(int argc, char* argv[]){

printf("Hello MPI World the original.\n");

int my_rank; /* rank of process */

int p; /* number of processes */

int source; /* rank of sender */

int dest; /* rank of receiver */

int tag=0; /* tag for messages */

char message[100], *tmp; /* storage for message */

MPI_Status status ; /* return status for receive */

int * array;

/* start up MPI */

array = (int *)malloc(sizeof(int) * 10);

MPI_Init(&argc, &argv);

/* find out process rank */

MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

/* find out number of processes */

MPI_Comm_size(MPI_COMM_WORLD, &p);

MPI_Barrier(MPI_COMM_WORLD);

if (my_rank !=0){

/* create message */

sprintf(message, "Greetings from process %d!", my_rank);

dest = 0;

/* use strlen+1 so that '\0' get transmitted */

MPI_Send(message, strlen(message)+1, MPI_CHAR,

dest, tag, MPI_COMM_WORLD);

MPI_Barrier(MPI_COMM_WORLD);

}

else{

printf("From process 0: Num processes: %d\n",p);

for (source = 1; source < p; source++) {

MPI_Recv(message, 100, MPI_CHAR, source, tag,

MPI_COMM_WORLD, &status);

printf("%s\n",message);

}

MPI_Barrier(MPI_COMM_WORLD);

}

/* shut down MPI */

MPI_Finalize();

free(array);

return 0;

}

if

for

IBM Research

© 2006 IBM Corporation

7

Control Flow Graphentry

printf

Int my_rank

Int source

Int p

Char message[100], *tmp

Int tag = 0

Int dest

MPI_Init()

MPI_Status status

array = malloc()

Int *array

MPI_Comm_rank()

MPI_Comm_size

my_rank != 0

dest = 0

sprintf

MPI_Barrier()

A

A

MPI_Barrier()

MPI_Send()

free(array)

(join block)

MPI_Barrier()

source ++

printf

MPI_Recv

source < p

source = 1

printf

MPI_Finalize()

B

B

return 0

exitif

for

IBM Research

© 2006 IBM Corporation

8

Data Dependence Graph (DDG)entry

printf

Int my_rank

Int source

Int p

Char message[100], *tmp

Int tag = 0

Int dest

MPI_Init()

MPI_Status status

array = malloc()

Int *array

MPI_Comm_rank()

MPI_Comm_size

my_rank != 0

dest = 0

sprintf

MPI_Barrier()

A

A

MPI_Barrier()

MPI_Send()

free(array)

(join block)

MPI_Barrier()

source ++

printf

MPI_Recv

source < p

source = 1

printf

MPI_Finalize()

B

B

return 0

exit

Control flowData flowControl flow

Work in Progress(graph not complete)

IBM Research

© 2006 IBM Corporation

9

Summary

MPI Barrier Analysis uses these structures

Is this valuable as an addition to CDT?

Other Future plans

– Parallel Tools Platform (PTP) Analysis:• Static and Dynamic Analysis of MPI, OpenMP, and LAPI

programs for detection of common errors• Code Refactorings for Performance Optimization, e.g.

refactoring for improved computation / communication overlap