[Bug c/19449] __builtin_constant_p cannot resolve to const when optimizing

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19449

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-03-28 08:53:54 UTC ---
Created attachment 29742
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29742
gcc49-pr19449.patch

Untested patch.  There is another case where we'd better fold
__builtin_constant_p right away, for static/extern function-local array
dimensions:
int y;
static char a[__builtin_constant_p (y) ? -1 : 1];
extern char b[__builtin_constant_p (y) ? -1 : 1];
char d[__builtin_constant_p (y) ? -1 : 1];

void
foo (int x)
{
  static char e[__builtin_constant_p (x) ? -1 : 1];
  extern char f[__builtin_constant_p (x) ? -1 : 1];
  auto char g[__builtin_constant_p (x) ? -1 : 1];
  char h[__builtin_constant_p (x) ? -1 : 1];
}

Right now this compiles fine for -O0, but for -O1 and above it errors on e and
f (twice on the latter actually).  When cfun == NULL, we always fold
__builtin_constant_p right away, but when cfun is NULL, we don't consider
static/extern.  Not sure how to fix this issue though, because I think the
declspecs aren't passed down to declarator parsing.