[Bug tree-optimization/16856] Missed optimisation opportunity with -O2

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16856

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |steven at gcc dot gnu.org
         Resolution|                            |FIXED

--- Comment #2 from Steven Bosscher <steven at gcc dot gnu.org> 2011-05-22 
15:24:48 UTC ---
$ cat t.c
static int bar;
static long baz;

int foo (_Bool x)
{
  int y;
  if (x) {
      ++baz;
      y = bar;
  }
  else {
      y = bar;
      ++baz;
  }
  return y;
}

$ ./cc1 -quiet -m32 -O2 t.c -fdump-tree-optimized
$ cat t.c.143t.optimized 

;; Function foo (foo)

foo (_Bool x)
{
  long int baz.1;
  long int baz.0;

<bb 2>:
  if (x_2(D) != 0)
    goto <bb 3>;
  else
    goto <bb 4>;

<bb 3>:
  baz.0_3 = baz;
  baz.1_4 = baz.0_3 + 1;
  baz = baz.1_4;
  goto <bb 5>;

<bb 4>:
  baz.0_7 = baz;
  baz.1_8 = baz.0_7 + 1;
  baz = baz.1_8;

<bb 5>:
  return 0;

}


$ cat t.s
    .file    "t.c"
    .text
    .p2align 4,,15
    .globl    foo
    .type    foo, @function
foo:
.LFB0:
    .cfi_startproc
    addl    $1, baz
    xorl    %eax, %eax
    ret
    .cfi_endproc
.LFE0:
    .size    foo, .-foo
    .local    baz
    .comm    baz,4,4
    .ident    "GCC: (GNU) 4.6.0 20110312 (experimental) [trunk revision
170907]"
    .section    .note.GNU-stack,"",@progbits