[Bug c/113647] New: __builtin_eh_return_data_regno ICEs when passed -1 as argument

[gabravier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113647

            Bug ID: 113647
           Summary: __builtin_eh_return_data_regno ICEs when passed -1 as
                    argument
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

int f()
{
    return __builtin_eh_return_data_regno(-1);
}

This crashes GCC with the following error:

during RTL pass: expand
<source>: In function 'int f()':
<source>:440:42: internal compiler error: in tree_to_uhwi, at tree.cc:6472
  440 |     return __builtin_eh_return_data_regno(-1);
      |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
0x2647edc internal_error(char const*, ...)
        ???:0
0xa51cb7 fancy_abort(char const*, int, char const*)
        ???:0
0xf34aa6 expand_builtin_eh_return_data_regno(tree_node*)
        ???:0
0xf6381c expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
expand_modifier, rtx_def**, bool)
        ???:0
0xf6ef5e store_expr(tree_node*, rtx_def*, int, bool, bool)
        ???:0
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Compiler returned: 1

This seems to be due to the following code:

```
rtx
expand_builtin_eh_return_data_regno (tree exp)
{
  tree which = CALL_EXPR_ARG (exp, 0);
  unsigned HOST_WIDE_INT iwhich;

  if (TREE_CODE (which) != INTEGER_CST)
    {
      error ("argument of %<__builtin_eh_return_regno%> must be constant");
      return constm1_rtx;
    }

  iwhich = tree_to_uhwi (which); // <-- THIS
```

wherein it looks like `tree_to_uhwi` asserts that its argument is non-negative,
meaning -1 (and all other negative numbers) fail.