re PR middle-end/65958 (-fstack-check breaks alloca on architectures using generic stack checking)

	PR middle-end/65958
	* config/aarch64/aarch64-protos.h (aarch64_output_probe_stack-range):
	Declare.
	* config/aarch64/aarch64.md: Declare UNSPECV_BLOCKAGE and
	UNSPEC_PROBE_STACK_RANGE.
	(blockage): New instruction.
	(probe_stack_range_<PTR:mode>): Likewise.
	* config/aarch64/aarch64.c (aarch64_emit_probe_stack_range): New
	function.
	(aarch64_output_probe_stack_range): Likewise.
	(aarch64_expand_prologue): Invoke aarch64_emit_probe_stack_range if
	static builtin stack checking is enabled.
	* config/aarch64/aarch64-linux.h (STACK_CHECK_STATIC_BUILTIN):
	Define to 1.

Co-Authored-By: Tristan Gingold <gingold@adacore.com>

From-SVN: r231259