Redundant malloc in structure optimization? (testsuite/gcc.dg/struct/wo_prof_global_var.c)

[Bingfeng Mei]

Hello, 
I am looking at a testsuite failure (wo_prof_global_var.c) in my
porting. Somehow, I found GCC 4.3.0 seems to generate unnecessary malloc
during structure optimization. In the code, the structure is split into
two individual fields (D.2240 and D.2242) and they are allocated
separately. But the original structure (D.2215) is still allocated, and
not used afterward.  The following RTL-level optimization cannot
eliminate it. 

Cheers,
Bingfeng Mei
Broadcom UK
 
Original C code: 
 
/* { dg-do compile } */
/* { dg-do run } */
 
#include <stdlib.h>
typedef struct
{
  int a;
  float b;
}str_t;
 
#define N 1000
 
str_t *p;
 
int
main ()
{
  int i, sum;
 
  p = malloc (N * sizeof (str_t));
  for (i = 0; i < N; i++)
    p[i].a = p[i].b + 1;
 
  for (i = 0; i < N; i++)
    if (p[i].a != p[i].b + 1)
      abort ();
 
  return 0;
}

.final_cleanup
 
/*----------------------------------------------------------------------
----*/
/* { dg-final { scan-ipa-dump "Number of structures to transform is 1"
"ipa_struct_reorg" } } */
/* { dg-final { cleanup-ipa-dump "*" } } */


;; Function main (main)
 
main ()
{
  int i.43;
  unsigned int D.2245;
  unsigned int D.2243;
  void * D.2242;
  void * D.2240;
  struct struct.0_sub.1 * p.0.4;
  struct struct.0_sub.0 * p.0.3;
  int i;
  void * D.2215;
 
<bb 2>:
  D.2215 = malloc (8000);
  D.2240 = malloc (4000);
  p.0.3 = (struct struct.0_sub.0 *) D.2240;
  D.2242 = malloc (4000);
  p.0.4 = (struct struct.0_sub.1 *) D.2242;
  p = (struct str_t *) D.2215;
  p.1 = p.0.4;
  p.0 = p.0.3;
  i = 0;
 
<bb 3>:
  D.2243 = (unsigned int) i << 2;
  (p.0.4 + D.2243)->a = (int) ((p.0.3 + D.2243)->b + 1.0e+0);
  i = i + 1;
  if (i != 1000)
    goto <bb 3>;
  else
    goto <bb 4>;
 
<bb 4>:
  i.43 = 0;
 
<bb 5>:
  D.2245 = (unsigned int) i.43 << 2;
  if ((float) (p.0.4 + D.2245)->a != (p.0.3 + D.2245)->b + 1.0e+0)
    goto <bb 6>;
  else
    goto <bb 7>;
 
<bb 6>:
  abort ();
 
<bb 7>:
  i.43 = i.43 + 1;
  if (i.43 != 1000)
    goto <bb 5>;
  else
    goto <bb 8>;
 
<bb 8>:
  return 0;
 
}