[Bug middle-end/20290] [4.0/4.1 Regression] Miscompilation on ppc with -Os

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-03-02 
20:44 ---
Note this also happens on powerpc-darwin too but that would mean it is just 
semi ppc specific.

-- 
   What|Removed |Added

 CC||pinskia at gcc dot gnu dot
   ||org
  Component|rtl-optimization|middle-end
Summary|[4.0 Regression]|[4.0/4.1 Regression]
   |Miscompilation on ppc with -|Miscompilation on ppc with -
   |Os  |Os


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20290

[Bug middle-end/20290] [4.0/4.1 Regression] Miscompilation on ppc with -Os

[jakub at gcc dot gnu dot org]

--- Additional Comments From jakub at gcc dot gnu dot org  2005-03-02 21:16 
---
It seems loop_iterations incorrectly counts number of iterations of the second
loop:
  ivtmp.2 = 113;
  goto bb 4 (L4);

L3:;
  *(ivtmp.52 + 4294967292B) = 9;
  i = i + 1;

L4:;
  ivtmp.2 = ivtmp.2 - 1;
  ivtmp.52 = ivtmp.52 + 4B;
  if (ivtmp.2 != 0) goto L3; else goto L16;

L16:;

loop's n_iterations is 113, but only the loop header is executed 113 times,
while the loop body is executed only 112 times.

-- 
   What|Removed |Added

 AssignedTo|unassigned at gcc dot gnu   |jakub at gcc dot gnu dot org
   |dot org |
 Status|NEW |ASSIGNED
   Last reconfirmed|2005-03-02 20:40:05 |2005-03-02 21:16:56
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20290

[Bug middle-end/20290] [4.0/4.1 Regression] Miscompilation on ppc with -Os

[jakub at gcc dot gnu dot org]

--- Additional Comments From jakub at gcc dot gnu dot org  2005-03-02 23:09 
---
The bug goes away with -Os -floop-optimize2, it is just the old loop optimizer
that doesn't handle this properly.  It seems to me that loop.c really can't
do its job correctly if it doesn't detect where the loop header and latch
are and if a BIV increments are done in header, latch or body.

Zdenek, any ideas what to do with this?

-- 
   What|Removed |Added

 CC||rakdver at gcc dot gnu dot
   ||org
 AssignedTo|jakub at gcc dot gnu dot org|unassigned at gcc dot gnu
   ||dot org
 Status|ASSIGNED|NEW


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20290

[Bug middle-end/20290] [4.0/4.1 Regression] Miscompilation on ppc with -Os

[jakub at gcc dot gnu dot org]

-- 
   What|Removed |Added

   Severity|normal  |critical


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20290

[Bug middle-end/20290] [4.0/4.1 Regression] Miscompilation on ppc with -Os

[rakdver at gcc dot gnu dot org]

--- Additional Comments From rakdver at gcc dot gnu dot org  2005-03-02 
23:15 ---
As for 4.1, I hope we will get rid of the old loop optimizer.
I will check what can be done in 4.0.

-- 
   What|Removed |Added

 AssignedTo|unassigned at gcc dot gnu   |rakdver at gcc dot gnu dot
   |dot org |org
 Status|NEW |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20290