[Bug tree-optimization/21451] New: Missed constant propagation

[steven at gcc dot gnu dot org]

This test case is not fully optimized on mainline: 
 
------------------------------------ 
typedef int (*objc_typed_write_func) (void *, const char *, int); 
typedef struct objc_typed_stream 
{ 
  void *physical; 
  objc_typed_write_func write; 
} TypedStream; 
 
int 
foo (struct objc_typed_stream *stream, unsigned int val) 
{ 
  unsigned char buf[sizeof (unsigned int) + 1]; 
 
  int len; 
  if ((val & 0x1fU) == val) 
    { 
      buf[0] = val | 0x20U; 
      len = 1; 
    } 
  else 
    { 
      int c, b; 
 
      buf[0] = 0x40U; 
 
      for (c = sizeof (int); c != 0; c -= 1) 
        if (((val >> (8 * (c - 1))) % 0x100) != 0) 
          break; 
 
      buf[0] |= c; 
 
      for (b = 1; c != 0; c--, b++) 
        { 
          buf[b] = (val >> (8 * (c - 1))) % 0x100; 
        } 
 
      len = b; 
    } 
  return (*stream->write) (stream->physical, buf, len); 
} 
------------------------------------ 
 
---> (in the .optimized dump): 
 
  # BLOCK 3 
  # PRED: 2 [95.0%]  (false,exec) 
<L3>:; 
  cD.1575_38 = cD.1575_46 - 1; 
  ivtmp.25D.1650_58 = ivtmp.25D.1650_18 - 8; 
  if (cD.1575_38 != 0) goto <L2>; else goto <L24>; 
  # SUCC: 2 [89.0%]  (dfs_back,true,exec) 9 [11.0%]  (loop_exit,false,exec) 
 
(...) 
  # BLOCK 9 
  # PRED: 3 [11.0%]  (loop_exit,false,exec) 
Invalid sum of outgoing probabilities 0.0% 
Invalid sum of incoming frequencies 1045, should be 0 
  # cD.1575_13 = PHI <cD.1575_38(3)>; 
<L24>:; 
  D.1592_60 = (signed charD.9) cD.1575_13; 
  D.1593_61 = D.1592_60 | 64; 
  D.1594_62 = (unsigned charD.10) D.1593_61; 
  #   bufD.1573_63 = V_MAY_DEF <bufD.1573_15>; 
  bufD.1573[0] = D.1594_62; 
  goto <bb 8> (<L9>); 
  # SUCC: 8 (fallthru,exec) 
 
cD.1575_13 is equal to 0 on entry of basic block 9.  We don't propagate 
this constant until GCSE CPROP1. 
 
Maybe the new pass order from the tree-cleanup-branch will fix this, 
which is why I've added Diego to the CC list.

-- 
           Summary: Missed constant propagation
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, TREE
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: steven at gcc dot gnu dot org
                CC: dnovillo at redhat dot com,gcc-bugs at gcc dot gnu dot
                    org,kazu at cs dot umass dot edu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21451