[Bug lto/114574] [14 regression] ICE when building curl with LTO (fld_incomplete_type_of, at ipa-free-lang-data.cc:257) since r14-9763

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114574

--- Comment #31 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I've tried to construct a wrong-code testcase, but so far haven't been
successful.
In e.g.
struct S { int s; } s;
struct T { long l; } t;

const struct S *
foo (const struct S **p, const struct T **q)
{
  *p = &s;
  *q = &t;
  return *p;
}
fre1 optimizes the return *p to return &s;
So I've tried
[[gnu::always_inline]] static inline const void *
foo (void *x, bool y)
{
  const struct S **p = (const struct S **) x;
  struct S { int s; };
  static struct S s;
  if (y)
    *p = &s;
  return *p;
}

[[gnu::always_inline]] static inline void
bar (void *x)
{
  const struct S **q = (const struct S **) x;
  struct S { int s; };
  static struct S s;
  *q = &s;
}

const void *
baz (void *x, void *y)
{
  foo (x, true);
  bar (y);
  return foo (x, false);
}
where without the posted patch I think the TYPE_CANONICAL on const struct S*
should be wrong in the bar function, but strangely we don't optimize it.