[Bug tree-optimization/103121] [12 Regression] Warnings in cp/optimize.c causing build failure

[msebor at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103121

--- Comment #31 from Martin Sebor <msebor at gcc dot gnu.org> ---
I believe I understand what both of you are saying and (also) that the cache
behaves correctly.  It stores offsets based on the pointer definition
statements.  Here's a test that I think reproduces the conditions you describe,
along with a dump of the access pass.  The cache contents show the offset has
the range [0, 3] (negative offsets are invalid and so they were eliminated, as
were offsets in excess of 3).  Stepping through the pointer_query code shows
that the offset cached for the p_6 pointer is derived from the 'p_6 = &a + _1;'
statement.

(The duplicate pointer_query cache contents (again) dump is a bug that I should
fix.)

Let me know if I misunderstood something.

$ cat x.c && gcc -O2 -S -fdump-tree-waccess3-details=/dev/stdout x.c
char a[3];

void g (int i, const void *s, int n)
{
  int j = i + 1;

  char *p = a + j;

  if (j == 7)
    __builtin_memcpy (p, s, n);

  __builtin_memset (p, 0, 3);
}

;; Function g (g, funcdef_no=0, decl_uid=1984, cgraph_uid=1, symbol_order=1)

 Registering value_relation (j_5 > i_4(D)) (bb2) at j_5 = i_4(D) + 1;
pointer_query counters:
  index cache size:   19
  index entries:      2
  access cache size:  4
  access entries:     2
  hits:               1
  misses:             2
  failures:           0
  max_depth:          1

pointer_query cache contents:
  6.0[3]: p_6 = &a + [0, 3] (base0); size: 3
  9.0[1]: s_9(D) = s_9(D); size: unknown


pointer_query cache contents (again):
  6.0: p_6 = &a + [0, 3] (base0); size: 3
  9.0: s_9(D) = s_9(D); size: unknown
void g (int i, const void * s, int n)
{
  char * p;
  int j;
  sizetype _1;
  long unsigned int _2;

  <bb 2> [local count: 1073741824]:
  j_5 = i_4(D) + 1;
  _1 = (sizetype) j_5;
  p_6 = &a + _1;
  if (j_5 == 7)
    goto <bb 3>; [20.24%]
  else
    goto <bb 4>; [79.76%]

  <bb 3> [local count: 217325344]:
  _2 = (long unsigned int) n_8(D);
  __builtin_memcpy (p_6, s_9(D), _2);

  <bb 4> [local count: 1073741824]:
  __builtin_memset (p_6, 0, 3); [tail call]
  return;

}