[Bug tree-optimization/16447] New: out of ssa generates bloated code

["dann at godzilla dot ics dot uci dot edu" <gcc-bugzilla at gcc dot gnu dot org>]

The the .tailc dump for the function combine.c:cant_combine_insn_p
looks like this: 
[snip]
<L23>:;
  T.150_24 = dest_5->u.fld[0].rtuint;
  if (T.150_24 > 52) goto <L35>; else goto <L24>;

<L24>:;
  T.151_26 = fixed_regs[T.150_24];
  if (T.151_26 != 0) goto <L35>; else goto <L25>;

<L25>:;
  T.152_29 = regclass_map[T.150_24];
  T.153_30 = T.152_29 - 1;
  if (T.153_30 <= 3) goto <L35>; else goto <L26>;

<L26>:;
  if (T.152_29 == 7) goto <L35>; else goto <L27>;

<L27>:;
  if (T.152_29 == 5) goto <L35>; else goto <L28>;

<L28>:;
  if (T.152_29 == 6) goto <L35>; else goto <L29>;

<L29>:;
  if (T.152_29 == 13) goto <L35>; else goto <L30>;

<L30>:;
  if (T.152_29 == 14) goto <L31>; else goto <L35>;

<L31>:;

  # T.139_1 = PHI <0(7), 1(25), 0(2), 1(0), 0(24), 0(8), 1(23), 1(22), 1(21),
1(20), 1(19), 0(18), 0(17), 1(16), 1(15), 1(14), 1(13), 1(12), 1(11)>;
<L35>:;
  return T.139_1;

Note the return value T.139_1

The .optimized dump looks like: 

[snip]
<L75>:;
  T.139 = 1;
  goto <bb 26> (<L35>);

<L27>:;
  if (T.152 == 5) goto <L76>; else goto <L28>;

<L76>:;
  T.139 = 1;
  goto <bb 26> (<L35>);

<L28>:;
  if (T.152 == 6) goto <L77>; else goto <L29>;

<L77>:;
  T.139 = 1;
  goto <bb 26> (<L35>);

<L29>:;
  if (T.152 == 13) goto <L78>; else goto <L30>;

<L78>:;
  T.139 = 1;
  goto <bb 26> (<L35>);

<L30>:;
  if (T.152 == 14) goto <L31>; else goto <L79>;

<L79>:;
  T.139 = 0;
  goto <bb 26> (<L35>);

<L31>:;
  T.139 = 1;

<L35>:;
  return T.139;

Not that T.139 is assigned 1 in a lot of BBs, followed by a jumb to the return
statement. 
The code would be much smaller if there was a only 1 assignment that all the ifs
jump to.

-- 
           Summary: out of ssa generates bloated code
           Product: gcc
           Version: 3.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dann at godzilla dot ics dot uci dot edu
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16447