internal compiler error: SSA corruption

[Jesse]

Ubuntu version: 20.04.1 LTS
GCC version: gcc-10 (Ubuntu 10.2.0-5ubuntu1~20.04) 10.2.0
Minimal preprocessed source code to reproduce:

```c
a() {
  int b;
  __sigsetjmp();
  for (;;) {
    if (b)
      b = c();
    d();
  }
}
```

Command to reproduce: `gcc-10 -O3 -c rofl.c` gives the following error:

```
rofl.c:1:1: warning: return type defaults to ‘int’ [-Wimplicit-int]
    1 | a() {
      | ^
rofl.c: In function ‘a’:
rofl.c:3:3: warning: implicit declaration of function ‘__sigsetjmp’ [-Wimplicit-function-declaration]
    3 | __sigsetjmp();
      | ^~~~~~~~~~~
rofl.c:6:11: warning: implicit declaration of function ‘c’ [-Wimplicit-function-declaration]
    6 | b = c();
      | ^
rofl.c:7:5: warning: implicit declaration of function ‘d’ [-Wimplicit-function-declaration]
    7 | d();
      | ^

Unable to coalesce ssa_names 2 and 4 which are marked as MUST COALESCE.
b_2(ab) and b_4(ab)
during RTL pass: expand
rofl.c:1:1: internal compiler error: SSA corruption
    1 | a() {
      | ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-10/README.Bugs> for instructions.
```

I tried reproduce with a recent snapshot. Since gcc-snapshot in focal is actually older than gcc-10, I tried it under groovy instead. And indeed, I was able to reproduce in groovy's gcc-snapshot ( 11.0.0 20200917 (experimental) [master revision c12facd2288:cb0617a790f:9fcedcc39153cb3cfa08ebab20aef6cdfb9ed609]) using a slightly different repro:

```c
a;
b() {
  int c, d;
  __sigsetjmp();
  for (; a;)
    for (; d;) {
      if (c)
        c = e();
      f();
    }
}
```

This file, when compiled with gcc-snapshot, leads to the following output:

```
rofl11.c:1:1: warning: data definition has no type or storage class
    1 | a;
      | ^
rofl11.c:1:1: warning: type defaults to 'int' in declaration of 'a' [-Wimplicit-int]
rofl11.c:2:1: warning: return type defaults to 'int' [-Wimplicit-int]
    2 | b() {
      | ^
rofl11.c: In function 'b':
rofl11.c:4:3: warning: implicit declaration of function '__sigsetjmp' [-Wimplicit-function-declaration]
    4 | __sigsetjmp();
      | ^~~~~~~~~~~
rofl11.c:8:13: warning: implicit declaration of function 'e' [-Wimplicit-function-declaration]
    8 | c = e();
      | ^
rofl11.c:9:7: warning: implicit declaration of function 'f' [-Wimplicit-function-declaration]
    9 | f();
      | ^

Unable to coalesce ssa_names 3 and 4 which are marked as MUST COALESCE.
c_3(ab) and c_4(ab)
during RTL pass: expand
rofl11.c:2:1: internal compiler error: SSA corruption
    2 | b() {
      | ^
0x185ffa7 internal_error(char const*, ...)
 ???:0
0xe92b7d coalesce_ssa_name(_var_map*)
 ???:0
0xe33007 rewrite_out_of_ssa(ssaexpand*)
 ???:0
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-snapshot/README.Bugs> for instructions.
```

[Matthias Klose (doko)]

confirmed, and fixed in focal. will be updated when we update gcc-10 in focal again.

[Jesse (sbjesse)]

Notice my second repro triggers the same error message in both gcc-10 and gcc-snapshot in groovy. Can you confirm those are fixed as well? I haven't used launchpad much in the last 8 years, I can't figure out how to also tag gcc-10 (groovy) and gcc-snapshot (groovy).

[Jesse (sbjesse)]

hmmm, I really want to highlight gcc-snapshot (groovy) but can't figure out how to change "focal" to "groovy"

[Jesse (sbjesse)]

I think this still affects package GCC-10 on both focal and groovy. Specifically the second repro posted above still crashes GCC. I'm repeating it here for clarity:

```
a;
b() {
  int c, d;
  __sigsetjmp();
  for (; a;)
    for (; d;) {
      if (c)
        c = e();
      f();
    }
}

```

putting the repro into `/tmp/c.c` and running `gcc-10 -O3 -c /tmp/c.c` triggers the bug:

```
c.c:1:1: warning: data definition has no type or storage class
    1 | a;
      | ^
c.c:1:1: warning: type defaults to 'int' in declaration of 'a' [-Wimplicit-int]
c.c:2:1: warning: return type defaults to 'int' [-Wimplicit-int]
    2 | b() {
      | ^
c.c: In function 'b':
c.c:4:3: warning: implicit declaration of function '__sigsetjmp' [-Wimplicit-function-declaration]
    4 | __sigsetjmp();
      | ^~~~~~~~~~~
c.c:8:13: warning: implicit declaration of function 'e' [-Wimplicit-function-declaration]
    8 | c = e();
      | ^
c.c:9:7: warning: implicit declaration of function 'f' [-Wimplicit-function-declaration]
    9 | f();
      | ^

Unable to coalesce ssa_names 3 and 4 which are marked as MUST COALESCE.
c_3(ab) and c_4(ab)
during RTL pass: expand
c.c:2:1: internal compiler error: SSA corruption
    2 | b() {
      | ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-10/README.Bugs> for instructions.

```

I tried the same repro on hirsute today and cannot reproduce the error.

[Matthias Klose (doko)]

> I tried the same repro on hirsute today and cannot reproduce the error.

closing