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* [Bug rtl-optimization/37263]  New: [4.3/4.4 Regression] extra code for doloop with unsigned 32bit types on LP64
@ 2008-08-28  2:20 pinskia at gcc dot gnu dot org
  2008-09-16 16:23 ` [Bug rtl-optimization/37263] [4.3 " pinskia at gcc dot gnu dot org
                   ` (6 more replies)
  0 siblings, 7 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2008-08-28  2:20 UTC (permalink / raw)
  To: gcc-bugs

Take (again):
unsigned ReverseBits (unsigned index, unsigned NumBits)
{
  unsigned i, rev;

  for (i = rev = 0; i < NumBits; i++)
  {
    rev = (rev << 1) | (index & 1);
    index >>= 1;
  }
  return rev;
}

--- CUT ---
Currently we get:
.L.ReverseBits:
        cmpdi 0,4,0
        mr 0,3
        li 3,0
        beqlr 0
        addi 9,4,-1
        cmpwi 7,4,0
        rldicl 9,9,0,32
        addi 9,9,1
        mtctr 9
        beq- 7,.L8
        beq- 7,.L8

But since we know that any time cmpdi r4, 0/beq is true, then cmpwi r4, 0/beq
is also.  I think one of the issue is that doloop is also not generating
subregs with /s/u  on them, even though the original subregs have them.


-- 
           Summary: [4.3/4.4 Regression] extra code for doloop with unsigned
                    32bit types on LP64
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org
GCC target triplet: powerpc64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37263


^ permalink raw reply	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2011-06-27 11:36 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <bug-37263-4@http.gcc.gnu.org/bugzilla/>
2011-06-27 11:36 ` [Bug rtl-optimization/37263] [4.3 Regression] extra code for doloop with unsigned 32bit types on LP64 rguenth at gcc dot gnu.org
2008-08-28  2:20 [Bug rtl-optimization/37263] New: [4.3/4.4 " pinskia at gcc dot gnu dot org
2008-09-16 16:23 ` [Bug rtl-optimization/37263] [4.3 " pinskia at gcc dot gnu dot org
2008-09-16 16:24 ` pinskia at gcc dot gnu dot org
2008-11-20  1:00 ` cnstar9988 at gmail dot com
2009-01-24 10:27 ` rguenth at gcc dot gnu dot org
2009-04-16 15:43 ` pinskia at gcc dot gnu dot org
2009-08-04 12:42 ` rguenth at gcc dot gnu dot org
2010-05-22 18:26 ` rguenth at gcc dot gnu dot org

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