[Bug tree-optimization/92157] New: incorrect strcmp() == 0 result for unknown strings

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92157

            Bug ID: 92157
           Summary: incorrect strcmp() == 0 result for unknown strings
           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: ---

The strcmp optimization checked in r276773 doesn't handle the following case
correctly, causing regressions in the arj package.

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

__attribute__ ((noipa)) int f (const char *s)
{
  int n = __builtin_strlen (s);

  if (__builtin_strcmp (s, a) == 0)
    __builtin_abort ();

  return n;
}

int main (void)
{
  a[0] = '1';
  f ("");
}

;; Function f (f, funcdef_no=0, decl_uid=1931, cgraph_uid=1, symbol_order=1)

__attribute__((noipa, noinline, noclone, no_icf))
f (const char * s)
{
  <bb 2> [count: 0]:
  __builtin_abort ();

}



;; Function main (main, funcdef_no=1, decl_uid=1935, cgraph_uid=2,
symbol_order=2) (executed once)

main ()
{
  <bb 2> [local count: 1073741824]:
  a[0] = 49;
  f ("");
  return 0;

}