c.opt: Add -flax-vector-conversions.

c.opt: Add -flax-vector-conversions.

	gcc/
	* c.opt: Add -flax-vector-conversions.
	* c-typeck.c (convert_for_assignment): Pass flag to
	vector_types_convertible_p to allow emission of note.
	(digest_init): Likewise.
	(comptypes_internal): Use vector_types_convertible_p.
	* c-opts.c: Handle -flax-vector-conversions.
	* c-common.c (flag_lax_vector_conversions): New.
	(vector_types_convertible_p): Unless -flax-vector conversions
	has been passed, disallow conversions between vectors with
	differing numbers of subparts and/or element types.  If such
	a conversion is disallowed, possibly emit a note on the first
	occasion only to inform the user of -flax-vector-conversions.
	The new last argument specifies this.
	* c-common.h (flag_lax_vector_conversions): New.
	(vector_types_convertible_p): Add extra argument.
	* config/i386/i386.c (ix86_init_mmx_sse_builtins): Use
	char_type_node for V*QI type vectors.
	* config/rs6000/rs6000-c.c (altivec_overloaded_builtins):
	Update to satisfy new typechecking rules.
	* config/rs6000/altivec.h (vec_cmple): Use vec_cmpge.
	* doc/invoke.texi (C Dialect Options): Document
	-flax-vector-conversions.

	gcc/cp/
	* call.c (standard_conversion): Pass flag to
	vector_types_convertible_p to disallow emission of note.
	* typeck.c (convert_for_assignment): Pass flag to
	vector_types_convertible_p to allow emission of note.
	(ptr_reasonably_similar): Pass flag to vector_types_convertible_p
	to disallow emission of note.

	gcc/testsuite/
	* gcc.target/i386/20020531-1.c: Use "char" not "unsigned char"
	in __v8qi typedef.
	* gcc.target/powerpc/altivec-vec-merge.c (foo): Add casts.
	* gcc.dg/simd-1.c: Update dg-error directives to reflect new
	compiler behaviour.
	* gcc.dg/simd-5.c: Likewise.
	* gcc.dg/simd-6.c: Likewise.
	* g++.dg/conversion/simd1.C: Likewise.
	* g++.dg/conversion/simd3.C: Likewise.
	* g++.dg/ext/attribute-test-2.C (data): Add "vs" member.
	(main): Use it.

From-SVN: r120572