[Bug tree-optimization/83501] New: [8 Regression] strlen(a) not folded after strcpy(a, "...")

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83501

            Bug ID: 83501
           Summary: [8 Regression] strlen(a) not folded after strcpy(a,
                    "...")
           Product: gcc
           Version: 8.0
            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: ---

GCC 7 and prior folded into a constant the strlen call in the following simple
test case but GCC 8 no longer does.

$ cat z.c && gcc -O2 -S -Wall -fdump-tree-optimized=/dev/stdout z.c
extern char* stpcpy (char*, const char*);
extern char* strcpy (char*, const char*);

char a[4];

void f (void)
{
  strcpy (a, "abc");

  if (__builtin_strlen (a) != 3)
    __builtin_abort ();
}

;; Function f (f, funcdef_no=0, decl_uid=1899, cgraph_uid=0, symbol_order=1)

f ()
{
  long unsigned int _1;

  <bb 2> [local count: 1073741825]:
  MEM[(char * {ref-all})&a] = MEM[(char * {ref-all})"abc"];
  _1 = __builtin_strlen (&a);
  if (_1 != 3)
    goto <bb 3>; [0.00%]
  else
    goto <bb 4>; [99.96%]

  <bb 3> [count: 0]:
  __builtin_abort ();

  <bb 4> [local count: 1073312327]:
  return;

}