Re: Three Address Code

smitha_chandran@yahoo.com wrote:
>
> I would like to know if Three Address Code can be implemented in some
> way other then quadruple or triples.


In our C compiler platform LANCE, the three address code intermediate
representation (IR) is represented in the form of low-level C
statements.
The advantage of this is that the IR can be compiled
just like the original C source. This feature can be
used for validation of the C frontend and
the IR optimization passes.


I attach a small example that illustrates the translation
from C code to three address code.




/*******************************************************
                original C code
*******************************************************/


int A[10];


int f(int x,int y)
{
    return x + y - 1;
}


void main()
{
    int a,i;


    a = 1;
    for (i = 0; i < 10; i++)
    {
        a += i > 1 ? A[i] : f(2,3);
    }


}


/*******************************************************
                three address IR code
*******************************************************/


int A[10];


int f(int x_3,int y_4)
{
  int t1;
  int t2;


  /* 7 "demo.c" */
  /* return x + y - 1; */


                t1 = x_3 + y_4;
                t2 = t1 - 1;
                return t2;


}


void main()
{
  int a_7;
  int i_8;
  int t3;
  int t4;
  int t5;
  int t14;
  int t6;
  char *t7;
  int t8;
  char *t9;
  int *t10;
  int t11;
  int t12;
  int t13;




  /* 14 "demo.c" */
  /* a = 1; */


                a_7 = 1;


  /* 15 "demo.c" */
  /* for (i = 0; i < 10; i++) */


                i_8 = 0;
  LL5:


  /* 17 "demo.c" */
  /* a += i > 1 ? A[i] : f(2,3); */


                t6 = i_8 > 1;
                if (t6) goto LL3;


                t11 = f(2,3);
                t12 = t11;
                goto LL4;


  LL3:
                t9 = (char *)A;
                t8 = i_8 * 4;
                t7 = t9 + t8;
                t10 = (int *)t7;
                t12 = *t10;
  LL4:
                t13 = a_7 + t12;
                a_7 = t13;


  /* 15 "demo.c" */
  /* for (i = 0; i < 10; i++) */


                t5 = i_8 + 1;
                i_8 = t5;
                t3 = t5 < 10;
                if (t3) goto LL5;


                return;
}




--
Dr. Rainer Leupers
University of Dortmund, Dept. of Computer Science 12
Otto-Hahn-Str. 16, Room E23, D-44221 Dortmund, Germany
phone: +49 (0)231 755-6151, fax: -6116, mobile: +49 (0)177 2131146
email (office): leupers@ls12.cs.uni-dortmund.de
email (home): rainer@leupers.de
http://ls12-www.cs.uni-dortmund.de/~leupers

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