internal compiler error: in referenced_var_lookup, at tree-dfa.c

[Jay K]

So..we have a custom frontend.
That uses process boundaries to avoid GPL crossing into BSDish licensed code.
So maybe you don't want to help me. Understood.

But just in case:

We generate trees. Probably they aren't of great quality.
e.g. relatively devoid of types and do field accesses by offseting pointers and casting.
We do our own layout earlier. Not great, but that's how it is.


Currently we use gcc 4.5.1.
When I enable inlining on some architectures, e.g. Macosx/x86, much code yields:


../FPrint.m3: In function 'FPrint__xCombine':
../FPrint.m3:25:0: internal compiler error: in referenced_var_lookup, at tree-dfa.c:525
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.


Now I've spent a while debugging this. I'm not completely lazy.


The original source (again, not a standard frontend):

PROCEDURE xCombine (): INTEGER =
  BEGIN
    RETURN xFix32 (0);
  END xCombine;

PROCEDURE xFix32 (x: INTEGER): INTEGER =
  CONST a = 1;
  BEGIN
   IF Word.And (x, a) = 0 THEN
     RETURN 0;
   END;
   RETURN 0;
  END xFix32;

 -fdump-tree-all, 003t.original:

FPrint__xCombine ()
{
  int_32 D.985;
  int_32 M3_AcxOUs__result;

    int_32 M3_AcxOUs__result;
    int_32 D.985;
  D.985 = FPrint__xFix32 (0);
  <retval> = D.985;
  return <retval>;
}


FPrint__xFix32 (int_32 M3_AcxOUs_x)
{
  int_32 M3_AcxOUs__result;

    int_32 M3_AcxOUs__result;
  if ((M3_AcxOUs_x & 1) != 0)
    {
      goto <D.986>;
    }
  <retval> = 0;
  return <retval>;
  <D.986>:;
  <retval> = 0;
  return <retval>;
}



040t.release_ssa:
;; Function FPrint__xFix32 (FPrint__xFix32)

Released 0 names, 0.00%
FPrint__xFix32 (int_32 M3_AcxOUs_x)
{
  int_32 D.987;

<bb 2>:
  D.987_3 = M3_AcxOUs_x_2(D) & 1;
  if (D.987_3 != 0)
    goto <bb 4> (<L1>);
  else
    goto <bb 3>;

<bb 3>:
  <retval>_4 = 0;
  goto <bb 5>;

<L1>:
  <retval>_5 = 0;

<bb 5>:
  # <retval>_1 = PHI <<retval>_4(3), <retval>_5(4)>
  return <retval>_1;

}


Breakpoint 1, 0x0078f21a in copy_phis_for_bb (bb=0x4126a280, id=0xbffff5d8) at ../../gcc-4.5/gcc/tree-inline.c:1937
1937    {
(gdb) n
1938      basic_block const new_bb = (basic_block) bb->aux;
(gdb) 
1943      jaykrell_check_1();  doesn't do anything now, was helping debug 
(gdb) 
1945      for (si = gsi_start (phi_nodes (bb)); !gsi_end_p (si); gsi_next (&si))
(gdb) 
1947          tree res = { 0 }, new_res = { 0 };
(gdb) 
1948          gimple new_phi = { 0 };
(gdb) 
1949          edge new_edge = { 0 };
(gdb) 
1951          phi = gsi_stmt (si);
(gdb) 
1952          res = PHI_RESULT (phi);
(gdb) 
1953          new_res = res;
(gdb) 
1954          if (is_gimple_reg (res))
(gdb) 
1956          walk_tree (&new_res, copy_tree_body_r, id, NULL);
(gdb) 
1957          new_phi = create_phi_node (new_res, new_bb);  This line split up locally, ok.
(gdb) 
1958          SSA_NAME_DEF_STMT (new_res) = new_phi;
(gdb) call debug_referenced_vars()

Referenced variables in FPrint__xCombine: 7

Variable: D.1036, UID D.1036, int_32gimple_default_def 0x412130a8 1036

Variable: D.1041, UID D.1041, int_32gimple_default_def 0x412130a8 1041

Variable: .MEM, UID D.1038, <unnamed type>, is global, call clobberedgimple_default_def 0x412130a8 1038

Variable: M3_AcxOUs_x, UID D.1039, int_32gimple_default_def 0x412130a8 1039

Variable: D.1040, UID D.1040, int_32gimple_default_def 0x412130a8 1040

Variable: <retval>, UID D.979, int_32gimple_default_def 0x412130a8 979

Variable: D.985, UID D.985, int_32gimple_default_def 0x412130a8 985


(gdb) n
1959          FOR_EACH_EDGE (new_edge, ei, new_bb->preds)
(gdb) call debug_referenced_vars()

Referenced variables in FPrint__xCombine: 7

Variable: D.1036, UID D.1036, int_32gimple_default_def 0x412130a8 1036

Variable: D.1041, UID D.1041, int_32gimple_default_def 0x412130a8 1041

Variable: .MEM, UID D.1038, <unnamed type>, is global, call clobberedgimple_default_def 0x412130a8 1038

Variable: M3_AcxOUs_x, UID D.1039, int_32gimple_default_def 0x412130a8 1039

Variable: D.1093058884, UID D.1093058884, int_32gimple_default_def 0x412130a8 1093058884

Variable: <retval>, UID D.979, int_32gimple_default_def 0x412130a8 979

Variable: D.985, UID D.985, int_32gimple_default_def 0x412130a8 985


You can see D.1040 got overwritten with something else.
  And then later the assertion is that it is missing.
Is it valid for uids to be so high?


Any clues/tips?


Thanks much,
 - Jay