[Bug target/68390] New: Incorrect code due to indirect tail call of varargs function with hard float ABI

[kugan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68390

            Bug ID: 68390
           Summary: Incorrect code due to indirect tail call of varargs
                    function with hard float ABI
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kugan at gcc dot gnu.org
  Target Milestone: ---

__attribute__ ((noinline))
double direct(int x, ...)
{
  return x*x;
}

__attribute__ ((noinline))
double broken(double (*indirect)(int x, ...), int v)
{
  return indirect(v);
}

int main ()
{
  double d1, d2;
  int i = 2;
  d1 = broken (direct, i);
  if (d1 != i*i)
    {
      __builtin_abort ();
    }
  return 0;
}


Please note that we have a sibcall from "broken" to "indirect".

"direct" is variadic function so it is conforming to AAPCS base standard.

"broken" is a non-variadic function and will return the value in
floating point register for TARGET_HARD_FLOAT. Thus we should not be
doing sibcall here.