[Bug target/38621] [4.3/4.4 Regression] sh gcc unable to spill register when building ghostscript-gpl with -O2

[kkojima at gcc dot gnu dot org]

------- Comment #3 from kkojima at gcc dot gnu dot org  2008-12-25 03:38 -------
Here is an another reduced testcase.

struct s
{
  char a[512];
  int b;
  int c;
};

long long
foo (struct s *p, int m, int r)
{
  if (r == m)
    p->b = 3;
  p->c = 1;
  return m;
}

I've confirmed that this fails with the trunk compiler too.

The insn scheduling before reload permutes the insns of
the exit basic block like as:

;;   ======================================================
;;   -- basic block 5 from 18 to 38 -- before reload
;;   ======================================================

;;        0-->    18 r166=0x204                       
:(issue+load_store),nothing,memory
changing bb of uid 55
;;        0-->    55 {r170=r161<<0x1;t=r161<0x0;}      :issue,int
changing bb of uid 56
;;        1-->    56 r170=-t                           :issue,int
changing bb of uid 46
;;        1-->    46 r0=r161                           :issue
;;        2-->    19 r168=0x1                          :issue,int
changing bb of uid 47
;;        2-->    47 r1=r170                           :issue
;;        3-->    20 [r160+r166]=r168                 
:(issue+load_store),nothing,memory
;;        3-->    38 use r0                            :nothing

i.e. insn 46 r0=r161 is placed before insn 20.
Unfortunately insn 20 [r160+r166]=r168 requires r0 because
sh has r0 + reg addressing only.  -fno-schedule-insns gets
rid of the error, though I have no idea for the right solution
ATM.


-- 

kkojima at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
      Known to fail|4.3.2                       |4.3.2 4.4.0
           Priority|P3                          |P4
   Last reconfirmed|0000-00-00 00:00:00         |2008-12-25 03:38:20
               date|                            |
            Summary|[4.3 Regression] sh gcc     |[4.3/4.4 Regression] sh gcc
                   |unable to spill register    |unable to spill register
                   |when building ghostscript-  |when building ghostscript-
                   |gpl with -O2                |gpl with -O2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38621