nested functions on Arm

[Ulrich Drepper <drepper at redhat dot com>]

The nested function handling on Arm is completely broken in the
moment.  This prevents glibc from being used on Arm in the moment.

The problem is this piece from config/arm/arm.h:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/* Output assembler code for a block containing the constant parts
   of a trampoline, leaving space for the variable parts.

   On the ARM, (if r8 is the static chain regnum, and remembering that
   referencing pc adds an offset of 8) the trampoline looks like:
	   ldr 		r8, [pc, #0]
	   ldr		pc, [pc]
	   .word	static chain value
	   .word	function's address
   ??? FIXME: When the trampoline returns, r8 will be clobbered.  */
#define ARM_TRAMPOLINE_TEMPLATE(FILE)			\
{							\
  asm_fprintf (FILE, "\tldr\t%r, [%r, #0]\n",		\
	       STATIC_CHAIN_REGNUM, PC_REGNUM);		\
  asm_fprintf (FILE, "\tldr\t%r, [%r, #0]\n",		\
	       PC_REGNUM, PC_REGNUM);			\
  ASM_OUTPUT_INT (FILE, const0_rtx);			\
  ASM_OUTPUT_INT (FILE, const0_rtx);			\
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

r8 must be saved by the called function but the trampoline code
clobbers the register even before control reaches the actual function.

I append a program which current terminates with a SIGILL on Arm (I'm
using the mainline compiler from 20000909 but this shouldn't make a
difference).  It's not this specific code which I need to have
running, I just tried to construct a test case.  The test case should
probably be added to the test suite as well.

-- 
---------------.                          ,-.   1325 Chesapeake Terrace
Ulrich Drepper  \    ,-------------------'   \  Sunnyvale, CA 94089 USA
Red Hat          `--' drepper at redhat.com   `------------------------

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include <stdlib.h>

extern int foo (int a, int b, int (*fp) (int, int));


int
main (void)
{
  int sum = 0;
  int i;

  int nested (int a, int b)
    {
      if (a > 2 * b)
	return a - b;
      else
	return b - a;
    }

  for (i = 0; i < 10; ++i)
    {
      int j;

      for (j = 0; j < 10; ++j)
	{
	  int k;

	  for (k = 0; k < 10; ++k)
	    sum += foo (i, j > k ? j - k : k - j, nested);
	}
    }

  if (sum != 2300)
    abort ();

  exit (0);
}


int
foo (int a, int b, int (*fp) (int, int))
{
  return fp (a, b);
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~