i386: Optimize code generation of __mm256_zextsi128_si256(__mm_set1_epi8(-1))

i386: Optimize code generation of __mm256_zextsi128_si256(__mm_set1_epi8(-1))

gcc/ChangeLog:

	PR target/94962
	* config/i386/constraints.md (BH): New define_constraint.
	* config/i386/i386.cc (standard_sse_constant_p): Add return
	3/4 when operand matches new predicate.
	(standard_sse_constant_opcode): Add new alternative branch to
	return "vpcmpeqd".
	* config/i386/predicates.md
	(vector_all_ones_zero_extend_half_operand): New define_predicate.
	(vector_all_ones_zero_extend_quarter_operand): Ditto.
	* config/i386/sse.md: Add constraint to insn "mov<mode>_internal".

gcc/testsuite/ChangeLog:

	PR target/94962
	* gcc.target/i386/avx256-unaligned-load-1.c: Modify test.
	* gcc.target/i386/avx256-unaligned-store-1.c: Ditto.
	* gcc.target/i386/avx256-unaligned-store-2.c: Ditto.
	* gcc.target/i386/avx256-unaligned-store-3.c: Ditto.
	* gcc.target/i386/pr94962-1.c: New test.
	* gcc.target/i386/pr94962-2.c: Ditto.
	* gcc.target/i386/pr94962-3.c: Ditto.
	* gcc.target/i386/pr94962-4.c: Ditto.