GitLab

Bugzilla Link	110
Created on	Sep 01, 2005 08:24
Resolution	FIXED
Resolved on	Jun 16, 2008 13:08
Version	1.00beta
OS	All
Architecture	All
Attachments	tutu2.sac, rotate.sac, test.sac

Extended Description

The attached example behaves differently depending on whether or not Loop Invariant Removal is 
activated or not. As I am yet not sure where this bug does actually stem from, I will shortly discuss what 
I found out.
The example looks like this:
use Array: all;
use SimplePrint: all;
int main() {
  A = with (.<=iv=[x,y]<=.) {
        i = 0;
        do { 
          i = i+1;
        } while ( i+x<10);
      }
      genarray( [10,10],i);
   c = print( A);
   return(c);  
}
When stopping the compilation after the optimizations (currently -b13) the relevant part of the code 
looks like this:
 i = 0; 
  A = with ( _flat_7_iv )
        ([ 0, 0 ] <= _flat_7_iv=[_flat_5_x, _flat_6_y] (IDXS:_wlidx_88_A) < [ 10, 10 ]) { 
          do 
          {
              i__SSA0_1 = (i + 1); 
              _pinl_90___flat_88 = (i__SSA0_1 + _flat_5_x); 
              _pinl_91___flat_45 = (_pinl_90___flat_88 < 10); 
              i = i__SSA0_1; 
          }
          while (_pinl_91___flat_45);
        } : i__SSA0_1 ; 
      genarray( [ 10, 10 ]) /* IDX: _wlidx_88_A */; 
As we can now clearly see, the errornous behaviour stems from i being overwritten in the with-loop 
body. However, the problem IS NOT caused by Loop Invariant Removal as i = 0 does certainly not 
depend on the index vector and is thus moved out of the with-loop correctly.
The issue becomes even more dramatic in this slightly modified example whose execution does not 
terminate at all:
int main() {
  i = 0;
  A = with (.<=iv=[x,y]<=.) {
        do { 
          i = i+1;
        } while ( i+x<10);
      }
      genarray( [10,10],i);
   c = print( A);
   return(c+i);  
}
My guess is that this bug is caused by lac2fun. What do you think?
Cheers,
Kai