[AArch64] Fix selection of default CPU options at configure-time

	* config.gcc (aarch64*-*-*): Use ISA flags from aarch64-arches.def.
	Do not define target_cpu_default2 to generic.
	* config/aarch64/aarch64.h (TARGET_CPU_DEFAULT): Use generic cpu.
	* config/aarch64/aarch64.c (aarch64_override_options): Update comment.
	* config/aarch64/aarch64-arches.def (armv8-a): Use generic cpu.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@208508 138bc75d-0d04-0410-961f-82ee72b054a4
	PR tree-optimization/60454
	* tree-ssa-math-opts.c (find_bswap_1): Fix bswap detection.

	* gcc.c-torture/execute/pr60454.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@208509 138bc75d-0d04-0410-961f-82ee72b054a4