MIPS: PR target/78176 add -mlxc1-sxc1.

MIPS: PR target/78176 add -mlxc1-sxc1.

gcc/

	PR target/78176
	* config.gcc (supported_defaults): Add lxc1-sxc1.
	(with_lxc1_sxc1): Add validation.
	(all_defaults): Add lxc1-sxc1.
	* config/mips/mips.opt (mlxc1-sxc1): New option.
	* gcc/config/mips/mips.h (OPTION_DEFAULT_SPECS): Add a default for
	mlxc1-sxc1.
	(TARGET_CPU_CPP_BUILTINS): Add builtin_define for
	__mips_no_lxc1_sxc1.
	(ISA_HAS_LXC1_SXC1): Gate with mips_lxc1_sxc1.
	* gcc/doc/invoke.texi (-mlxc1-sxc1): Document the new option.
	* doc/install.texi (--with-lxc1-sxc1): Document the new option.

gcc/testsuite/

	* gcc.target/mips/lxc1-sxc1-1.c: New file.
	* gcc.target/mips/lxc1-sxc1-2.c: Likewise.
	* gcc.target/mips/mips.exp (mips_option_groups): Add ghost option
	HAS_LXC1.
	(mips_option_groups): Add -m[no-]lxc1-sxc1.
	(mips-dg-init): Detect default -mno-lxc1-sxc1.
	(mips-dg-options): Handle HAS_LXC1 arch upgrade/downgrade.

From-SVN: r244640