[Bug c++/91895] Compile the code with -O1 or -O2 is slower than with -O3 and -Os

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91895

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |marxin at gcc dot gnu.org
         Resolution|---                         |INVALID

--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
With GCC 9 we end up with the following code with -O and higher optimization
levels:

$ gcc pr91895.c -O -fdump-tree-optimized=/dev/stdout

;; Function foo (foo, funcdef_no=0, decl_uid=1915, cgraph_uid=1,
symbol_order=5)

foo ()
{
  <bb 2> [local count: 222998]:
  d = 17;
  c = 17;
  b = 17;
  a = 17;
  return;

}



;; Function main (main, funcdef_no=1, decl_uid=1930, cgraph_uid=2,
symbol_order=6) (executed once)

main ()
{
  <bb 2> [local count: 1073741824]:
  foo ();
  return 0;

}