[Bug tree-optimization/19038] [4.0 Regression] out of ssa causing loops to have more than one BB

["steven at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From steven at gcc dot gnu dot org  2005-01-21 13:18 -------
No, tree-ssa-live is quite right.  ivtmp.3_12 and ivtmp.3_20 are defined 
and live at some common statements, so they conflict: 
 
  # BLOCK 1 
  # PRED: 0 [88.4%]  (true,exec) 1 [89.0%]  (dfs_back,false,exec) 
  # ivtmp.3_12 = PHI <0(0), ivtmp.3_20(1)>; 
<L8>:; 
  D.501_28 = &__BLNK__.array1[ivtmp.3_12]; 
  #   __BLNK___11 = V_MAY_DEF <__BLNK___2>; 
  *D.501_28 = 1.0e+0; 
  ivtmp.3_20 = ivtmp.3_12 + 1; 
  D.503_30 = D.457_4 - 1; 
  D.504_31 = (<unnamed type>) D.503_30; 
  D.505_32 = D.504_31 + 1; 
  if (ivtmp.3_20 == D.505_32) goto <L12>; else goto <L8>; 
  # SUCC: 2 [11.0%]  (loop_exit,true,exec) 1 [89.0%]  (dfs_back,false,exec) 
 
  # BLOCK 2 
  # PRED: 1 [11.0%]  (loop_exit,true,exec) 
<L12>:; 
  D.497_22 = ivtmp.3_12 + 2; 
  lsm_tmp.2_23 = (int4) D.497_22; 
  #   j_7 = V_MUST_DEF <j_6>; 
  j = lsm_tmp.2_23; 
  # SUCC: 3 [100.0%]  (fallthru) 
 
Between "ivtmp.3_20 = ivtmp.3_12 + 1;" and "D.497_22 = ivtmp.3_12 + 2;" 
both versions of ivtmp.3 are live.  I have not looked at what causes this, 
but IMOH all passes should avoid letting induction variables escape a loop. 
 
Interesting note: I think "D.497_22 = ivtmp.3_12 + 2;" could be replaced 
with "D.497_22 = ivtmp.3_20 + 1;" which would fix this problem. 
 
 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19038