Hi,

this patch adds effective target stack_size.


Atm, -DSTACK_SIZE=<value> is defined at top-level in gcc_target_compile 
resulting in the macro being passed down to ~30k compilations. The macro 
is used in just 37 testcases.

The patch defines an effective target stack_size, which is used in 
individual test-cases to add -DSTACK_SIZE=<value> using:
- dg-additional-options, and
- a new directive dg-effective-target-value to get the value.


gccint.info (edited for long lines):
...
7.2.3.12 Other attributes
.........................

'stack_size'
      Target has limited stack size.  The stack size limit can be
      obtained using '[dg-effective-target-value stack_size]'.  For
      example:
           /* { dg-additional-options
	         "-DSTACK_SIZE=[dg-effective-target-value stack_size]"
                  { target { stack_size } } } */
...

Lightly tested sofar.

OK for trunk if x86_64 and nvptx testing succeeds?

Thanks,
- Tom