[Bug target/12395] Suboptimal code with global variables

[steven at gcc dot gnu dot org]

------- Comment #15 from steven at gcc dot gnu dot org  2010-02-12 21:58 -------
GCC still doesn't get it right for this PR. The .139t.optimized dump for trunk
r156706:

;; Function foo (foo)

foo ()
{
  int a.1;
  int a.0;

<bb 2>:
  a.0_1 = a;
  a.1_2 = a.0_1 + 1;
  a = a.1_2;
  if (a.1_2 != 0)
    goto <bb 3>;
  else
    goto <bb 4>;

<bb 3>:
  a.1_5 = a.1_2 + 1;
  a = a.1_5;

<bb 4>:
  return;

}


Assembly output on ix86 (with -O2 -fomit-frame-pointer):

foo:
        movl    a, %edx
        leal    1(%edx), %eax
        testl   %eax, %eax
        movl    %eax, a
        je      .L1
        addl    $2, %edx
        movl    %edx, a
.L1:
        rep
        ret


And on x86_64 (-O2):

foo:
.LFB0:
        .cfi_startproc
        movl    a(%rip), %edx
        leal    1(%rdx), %eax
        testl   %eax, %eax
        movl    %eax, a(%rip)
        je      .L1
        addl    $2, %edx
        movl    %edx, a(%rip)
.L1:
        rep
        ret
        .cfi_endproc


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2008-09-21 13:52:33         |2010-02-12 21:58:52
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12395