[Bug tree-optimization/86613] New: missing -Warray-bounds on a wide string access due to ccp folding

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86613

            Bug ID: 86613
           Summary: missing -Warray-bounds on a wide string access due to
                    ccp folding
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

Similar to bug 86611 but with a different root cause, GCC fails to diagnose the
out-of-bounds array index in the following test case, in both ilp32 and lp64. 
According to the dumps, the underlying root cause appears to be that the
invalid array dereference is folded in ccp1.

$ cat c.c && gcc -O2 -S -Warray-bounds -Wno-stringop-overflow
-fdump-tree-objsz=/dev/stdout -fdump-tree-ccp1=/dev/stdout c.c -m32
void f (int);

void h (void)
{
  __PTRDIFF_TYPE__ i = -__PTRDIFF_MAX__ - 1;
  f (L"123456789"[i]);
}


;; Function h (h, funcdef_no=0, decl_uid=1841, cgraph_uid=1, symbol_order=0)

h ()
{
  int i;
  long int _1;

  <bb 2> :
  i_2 = -2147483648;
  _1 = "1"[i_2];
  f (_1);
  return;

}



;; Function h (h, funcdef_no=0, decl_uid=1841, cgraph_uid=1, symbol_order=0)

h ()
{
  int i;
  long int _1;

  <bb 2> :
  _1 = "1"[-2147483648];
  f (_1);
  return;

}



;; Function h (h, funcdef_no=0, decl_uid=1841, cgraph_uid=1, symbol_order=0)

h ()
{
  <bb 2> [local count: 1073741825]:
  f (49);
  return;

}