rs6000: correct vector sign extend builtins on Big Endian

rs6000: correct vector sign extend builtins on Big Endian

gcc/
	PR target/108812
	* config/rs6000/vsx.md (vsx_sign_extend_qi_<mode>): Rename to...
	(vsx_sign_extend_v16qi_<mode>): ... this.
	(vsx_sign_extend_hi_<mode>): Rename to...
	(vsx_sign_extend_v8hi_<mode>): ... this.
	(vsx_sign_extend_si_v2di): Rename to...
	(vsx_sign_extend_v4si_v2di): ... this.
	(vsignextend_qi_<mode>): Remove.
	(vsignextend_hi_<mode>): Remove.
	(vsignextend_si_v2di): Remove.
	(vsignextend_v2di_v1ti): Remove.
	(*xxspltib_<mode>_split): Replace gen_vsx_sign_extend_qi_v2di with
	gen_vsx_sign_extend_v16qi_v2di and gen_vsx_sign_extend_qi_v4si
	with gen_vsx_sign_extend_v16qi_v4si.
	* config/rs6000/rs6000.md (split for DI constant generation):
	Replace gen_vsx_sign_extend_qi_si with gen_vsx_sign_extend_v16qi_si.
	(split for HSDI constant generation): Replace gen_vsx_sign_extend_qi_di
	with gen_vsx_sign_extend_v16qi_di and gen_vsx_sign_extend_qi_si
	with gen_vsx_sign_extend_v16qi_si.
	* config/rs6000/rs6000-builtins.def (__builtin_altivec_vsignextsb2d):
	Set bif-pattern to vsx_sign_extend_v16qi_v2di.
	(__builtin_altivec_vsignextsb2w): Set bif-pattern to
	vsx_sign_extend_v16qi_v4si.
	(__builtin_altivec_visgnextsh2d): Set bif-pattern to
	vsx_sign_extend_v8hi_v2di.
	(__builtin_altivec_vsignextsh2w): Set bif-pattern to
	vsx_sign_extend_v8hi_v4si.
	(__builtin_altivec_vsignextsw2d): Set bif-pattern to
	vsx_sign_extend_si_v2di.
	(__builtin_altivec_vsignext): Set bif-pattern to
	vsx_sign_extend_v2di_v1ti.
	* config/rs6000/rs6000-builtin.cc (lxvrse_expand_builtin): Replace
	gen_vsx_sign_extend_qi_v2di with gen_vsx_sign_extend_v16qi_v2di,
	gen_vsx_sign_extend_hi_v2di with gen_vsx_sign_extend_v8hi_v2di and
	gen_vsx_sign_extend_si_v2di with gen_vsx_sign_extend_v4si_v2di.

gcc/testsuite/
	PR target/108812
	* gcc.target/powerpc/p9-sign_extend-runnable.c: Set corresponding
	expected vectors for Big Endian.
	* gcc.target/powerpc/int_128bit-runnable.c: Likewise.

(cherry picked from commit a213e2c965382c24fe391ee5798effeba8da0fdf)