[Bug tree-optimization/83543] strlen of a local array member not optimized on some targets

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83543

--- Comment #6 from Martin Sebor <msebor at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #5)

The cutoff between (a) and (b) also depends on whether or not a function is
being optimized for speed or for size, so at -Os, the x86_64 target also uses
(b) for all sizes.

Here's a test case and its output with an x86_64 compiler:

$ cat t.c && gcc -S -Wall -fdump-tree-optimized=/dev/stdout t.c
#pragma GCC optimize ("O2")
int f (void)
{
  struct A { char a[4]; } a = { "123" };
  return __builtin_strlen (a.a);
}

#pragma GCC optimize ("Os")
int g (void)
{
  struct B { char b[4]; } b = { "123" };
  return __builtin_strlen (b.b);
}

;; Function f (f, funcdef_no=0, decl_uid=1957, cgraph_uid=0, symbol_order=0)

__attribute__((optimize ("O2")))
f ()
{
  <bb 2> [local count: 1073741825]:
  return 3;

}



;; Function g (g, funcdef_no=1, decl_uid=1963, cgraph_uid=1, symbol_order=1)

__attribute__((optimize ("O2", "Os")))
g ()
{
  struct B b;
  long unsigned int _1;
  int _4;

  <bb 2> [local count: 1073741825]:
  b.b = "123";
  _1 = __builtin_strlen (&b.b);
  _4 = (int) _1;
  b ={v} {CLOBBER};
  return _4;

}