7.3.1 Induction Variable Recognition

Induction variables are integer or floating point variables that are incremented or decremented the same amount for each for -loop iteration. Recognizing their relationship to the loop control variables often lifts data dependence restrictions and permits further optimization, as shown in the following example:


for ( i=0; i<n; i++ ) {

    a[j] = b[k];

    j++;

    k+=2;

    }

Becomes:


_Kii2 = k;

    _Kii1 = j;

      for ( i = 0; i<n; i++ ) {

      a[_Kii1+i] = b[_Kii2+i*2];

   }


Previous Page | Next Page | Contents | Index |
Command-Line Qualifiers

Copyright © Digital Equipment Corporation. 1999. All Rights Reserved.