Following testcase fails on ARM (from
https://bugs.linaro.org/show_bug.cgi?id=1900).

__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.

Attached patch fixes this. Bootstrap and regression testing is ongoing.
Is this OK if no issues with the testing?

Thanks,
Kugan

gcc/ChangeLog:

2015-11-17  Kugan Vivekanandarajah  <kuganv@linaro.org>

	* config/arm/arm.c (arm_function_ok_for_sibcall): Disable sibcall to
	indirect function when TARGET_HARD_FLOAT.

gcc/testsuite/ChangeLog:

2015-11-17  Kugan Vivekanandarajah  <kuganv@linaro.org>

	* gcc.target/arm/variadic_sibcall.c: New test.