attribs: Restrict decl_attributes DECL_FUNCTION_SPECIFIC_TARGET changes to targets...

attribs: Restrict decl_attributes DECL_FUNCTION_SPECIFIC_TARGET changes to targets that care about target attributes/pragmas [PR105234]

The following code is rejected e.g. on mips64el-linux (but I think many
other targets which don't support target attribute or pragma).
The problem is that the change to decl_attributes below is done
unconditionally and with just #pragma GCC push_options/pop_options pair
we have target_option_default_node NULL, but after popping options
target_option_current_node becomes non-NULL and this decl_attribute
spot fills in DECL_FUNCTION_SPECIFIC_TARGET of a subset of a functions.
Those appearing before push_options/pop_options will have it NULL and
as target_option_default_node is also NULL on those targets, the default
can_inline_p will refuse to inline any functions defined with NULL
DECL_FUNCTION_SPECIFIC_TARGET into any function with non-NULL
DECL_FUNCTION_SPECIFIC_TARGET (even when nothing in the options really
changed).

The following patch restricts that snippet to targets that care (initialize
target_option_default_node to non-NULL to the command line options early)
which include all targets that actually implement target attribute and/or
pragma.

2022-04-13  Jakub Jelinek  <jakub@redhat.com>

	PR target/105234
	* attribs.cc (decl_attributes): Don't set
	DECL_FUNCTION_SPECIFIC_TARGET if target_option_default_node is
	NULL.

	* gcc.c-torture/compile/pr105234.c: New test.