[PATCH] Regression in SPEC

[Sebastian Pop <sebastian dot pop at cri dot ensmp dot fr>]

Hello,

On Wed, Nov 03, 2004 at 09:30:12AM +0200, Ira Rosen wrote:
> 
> Hi Sebastian,
> 
> We got the following problem while compiling gap benchmark of SPEC2000:
> 
> /Develop/mainline_ira4_build2/bin/gcc -c -o vector.o  -DSYS_IS_BSD
> -DSYS_HAS_IOCTL_PROTO
> -DSYS_HAS_TIME_PROTO -DSYS_HAS_SIGNAL_PROTO -DSYS_HAS_ANSI
> -DSYS_HAS_CALLOC_PROTO
> -DSYS_HAS_STDIO_PROTO -fprofile-arcs -O3 -mcpu=G5 -mpowerpc64 -ffast-math
> -mdynamic-no-pic
> -freorder-blocks -fstrict-aliasing -ftree-vectorize -maltivec
> -fdump-tree-vect-stats
> -fdump-tree-vect-details   vector.c
> virtual memory exhausted: Cannot allocate memory
> specmake: *** [vector.o] Error 1
> 
> This does not happen without vectorization pass.
> I checked out a snapshot from October 13 that doesn't contain your patch (
> "Merge data dependence bits for interchanging swim loops"). It was OK. Then
> I applied your patch, and got the above error.
> 
> We can reduce the testcase to the following loop (the file with the
> complete testcase is attached):
> 
> unsigned long i;
> for (i = 0; i <= 5; i++)
>     {
>       ia[i][3] = 5;
>       ia[3][i] = 5;
>     }
> 
> Note, that if i is int, or instead of 3 there is some variable the problem
> doesn't occur.
> 
> The program gets stuck in analyze_array() function when it tries to
> allocate memory (res = xmalloc (sizeof (struct data_reference));), and
> after a while it returns with memory exhaustion error. This happens for the
> second reference: ia[3][i].
> 

The problem comes from the fact that the computation of the gcd
doesn't stop, and has nothing to do with the memory allocation.
Here is a patch that solves the problem:

	* tree.c (tree_fold_gcd): Use FLOOR_MOD_EXPR instead of
	CEIL_MOD_EXPR.

*** tree.c.~1.442.~	Tue Nov  2 20:08:25 2004
--- tree.c	Wed Nov  3 13:04:44 2004
*************** tree_fold_gcd (tree a, tree b)
*** 6029,6035 ****
  
    while (1)
      {
!       a_mod_b = fold (build2 (CEIL_MOD_EXPR, type, a, b));
  
        if (!TREE_INT_CST_LOW (a_mod_b)
  	  && !TREE_INT_CST_HIGH (a_mod_b))
--- 6029,6035 ----
  
    while (1)
      {
!       a_mod_b = fold (build2 (FLOOR_MOD_EXPR, type, a, b));
  
        if (!TREE_INT_CST_LOW (a_mod_b)
  	  && !TREE_INT_CST_HIGH (a_mod_b))