[Bug 1899114] Re: internal compiler error: SSA corruption

[Matthias Klose]

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


** Also affects: gcc-10 (Ubuntu Focal)
   Importance: Undecided
       Status: New

** Changed in: gcc-10 (Ubuntu Focal)
       Status: New => Triaged

** Changed in: gcc-10 (Ubuntu)
       Status: New => Fix Released

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Title:
  internal compiler error: SSA corruption

Status in gcc-10 package in Ubuntu:
  Fix Released
Status in gcc-10 source package in Focal:
  Triaged

Bug description:
  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.
  ```

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