What is wrong with my SSA (ICE in SSA name coalescing)?

[Ilya Enkovich]

Hi,

I'm testing GIMPLE instrumentation pass and having a trouble with SSA
name coalescing. I get such error only in tests with abnormal edges.
Here is a simple test I use:
void foo ();
void goo (char *);

int test ()
{
  char *name = 0;

  foo();

  _setjmp (0);

  if (!name) {
    name = "-";
  }

  goo(name);
  goo(0);

  return 0;
}

Here is GIMPLE after my instrumentation. Instrumentation
statements/expressions are marked with +++

test ()
{
+++<unnamed type> __tmp.0;+++
  char * name;
  int D.1761;
  int _5;

  <bb 10>:
+++__tmp.0_9 = __length_1;+++
+++__tmp.0_8(ab) = __zero_length;+++

  <bb 2>:
  name_3(ab) = 0B;
  foo ();

  <bb 3>:
  # name_1(ab) = PHI <name_3(ab)(2), name_1(ab)(3), name_2(ab)(6),
name_2(ab)(7)>
+++# __tmp.0_7(ab) = PHI <__tmp.0_8(ab)(2), __tmp.0_7(ab)(3),
__tmp.0_6(ab)(6), __tmp.0_6(ab)(7)>+++
  _setjmp (0);

  <bb 4>:
  if (name_1(ab) == 0B)
    goto <bb 5>;
  else
    goto <bb 6>;

  <bb 5>:
  name_4 = "-";

  <bb 6>:
  # name_2(ab) = PHI <name_1(ab)(4), name_4(5)>
+++# __tmp.0_6(ab) = PHI <__tmp.0_7(ab)(4), __tmp.0_9(5)>+++
  goo (name_2(ab), +++__tmp.0_6(ab)+++);

  <bb 7>:
  goo (0B, +++__tmp.0_8(ab)+++);

  <bb 8>:
  _5 = 0;

<L2>:
  return _5;

}

SSA name coalescing for this code later causes following error:

Unable to coalesce ssa_names 7 and 8 which are marked as MUST COALESCE.
__tmp.0_7(ab) and  __tmp.0_8(ab)
coalesce_test.c: In function 'test':
coalesce_test.c:5:1: internal compiler error: SSA corruption
 test ()
 ^
0xb5dc65 fail_abnormal_edge_coalesce
        ../../gcc-pl/gcc/tree-ssa-coalesce.c:934
0xb5f0ed coalesce_partitions
        ../../gcc-pl/gcc/tree-ssa-coalesce.c:1236
0xb5f837 coalesce_ssa_name()
        ../../gcc-pl/gcc/tree-ssa-coalesce.c:1373
0xafaca4 remove_ssa_form
        ../../gcc-pl/gcc/tree-outof-ssa.c:900
0xafb602 rewrite_out_of_ssa(ssaexpand*)
        ../../gcc-pl/gcc/tree-outof-ssa.c:1133
0x66cac9 gimple_expand_cfg
        ../../gcc-pl/gcc/cfgexpand.c:4480

What is actually wrong with my instrumentation? As I could understand
from debugging, coalescing succeeded for name_1 and name_3, but failed
for __tmp.0_7 and __tmp.0_8 because __tmp.0_8 has long lifetime (used
in BB 7). If I remove second goo call from the test, then error goes
away. Is it actually incorrect to have SSA names with such
intersecting lifetimes? BTW if I use another var than __tmp.0 for 8th
SSA name creation, then test passes.

Compiler modification is based on gcc (GCC) 4.9.0 20130422 (experimental).

Thanks,
Ilya