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* [Bug middle-end/35310]  New: Late struct expansion -- missing PRE (2)
@ 2008-02-23  5:27 xinliangli at gmail dot com
  2008-02-24 22:13 ` [Bug middle-end/35310] " rguenth at gcc dot gnu dot org
  2009-02-06 21:52 ` steven at gcc dot gnu dot org
  0 siblings, 2 replies; 4+ messages in thread
From: xinliangli at gmail dot com @ 2008-02-23  5:27 UTC (permalink / raw)
  To: gcc-bugs

union U {
   struct A {
     int a;
     int b;
  }aa;
  long long ll;
};

struct B{
   union U u1;
   union U u2;
} bg;
struct B bg;

struct B bar();
int foo (int n)
{
     if (n)
     {
        bg = bar();
     }

     return bg.u1.ll + bg.u2.ll;
};

// Two union fields loads are partially redundant.

gcc genearted code at -O2:

foo:
.LFB2:
        subq    $24, %rsp
.LCFI0:
        testl   %edi, %edi
        je      .L2
        xorl    %eax, %eax
        call    bar
        movq    %rax, bg(%rip)
        movq    %rdx, bg+8(%rip)
.L2:
        movq    bg(%rip), %rax
        addl    bg+8(%rip), %eax
        addq    $24, %rsp
        ret


-- 
           Summary: Late struct expansion -- missing PRE (2)
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: xinliangli at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35310


^ permalink raw reply	[flat|nested] 4+ messages in thread
* [Bug middle-end/35310] Late struct expansion -- missing PRE (2)
  2008-02-23  5:27 [Bug middle-end/35310] New: Late struct expansion -- missing PRE (2) xinliangli at gmail dot com
@ 2008-02-24 22:13 ` rguenth at gcc dot gnu dot org
  2009-02-06 21:52 ` steven at gcc dot gnu dot org
  1 sibling, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2008-02-24 22:13 UTC (permalink / raw)
  To: gcc-bugs



-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
           Keywords|                            |missed-optimization
            Version|unknown                     |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35310


^ permalink raw reply	[flat|nested] 4+ messages in thread
* [Bug middle-end/35310] Late struct expansion -- missing PRE (2)
  2008-02-23  5:27 [Bug middle-end/35310] New: Late struct expansion -- missing PRE (2) xinliangli at gmail dot com
  2008-02-24 22:13 ` [Bug middle-end/35310] " rguenth at gcc dot gnu dot org
@ 2009-02-06 21:52 ` steven at gcc dot gnu dot org
  1 sibling, 0 replies; 4+ messages in thread
From: steven at gcc dot gnu dot org @ 2009-02-06 21:52 UTC (permalink / raw)
  To: gcc-bugs



------- Comment #1 from steven at gcc dot gnu dot org  2009-02-06 21:52 -------
Confirmed.  Looks like something for postreload-gcse to handle.  Before that,
there are no partial redundancies in the RTL (at least, not in the quick look I
gave it).


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2009-02-06 21:52:19
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35310


^ permalink raw reply	[flat|nested] 4+ messages in thread
* [Bug middle-end/35310] Late struct expansion -- missing PRE (2)
       [not found] <bug-35310-4@http.gcc.gnu.org/bugzilla/>
@ 2012-10-31 21:17 ` xinliangli at gmail dot com
  0 siblings, 0 replies; 4+ messages in thread
From: xinliangli at gmail dot com @ 2012-10-31 21:17 UTC (permalink / raw)
  To: gcc-bugs


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35310

--- Comment #2 from davidxl <xinliangli at gmail dot com> 2012-10-31 21:17:27 UTC ---
GCC is still not generating good code here, neither does ICC.

However LLVM does a good job here.

David



(In reply to comment #1)
> Confirmed.  Looks like something for postreload-gcse to handle.  Before that,
> there are no partial redundancies in the RTL (at least, not in the quick look I
> gave it).


^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2012-10-31 21:17 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2008-02-23  5:27 [Bug middle-end/35310] New: Late struct expansion -- missing PRE (2) xinliangli at gmail dot com
2008-02-24 22:13 ` [Bug middle-end/35310] " rguenth at gcc dot gnu dot org
2009-02-06 21:52 ` steven at gcc dot gnu dot org
     [not found] <bug-35310-4@http.gcc.gnu.org/bugzilla/>
2012-10-31 21:17 ` xinliangli at gmail dot com

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