re PR target/36079 (cld instruction is not emitted anymore.)

re PR target/36079 (cld instruction is not emitted anymore.)

	PR target/36079
	* configure.ac: Handle --enable-cld.
	* configure: Regenerated.
	* config.gcc: Add USE_IX86_CLD to tm_defines for x86 targets.
	* config/i386/i386.h (struct machine_function): Add needs_cld field.
	(ix86_current_function_needs_cld): New define.
	* config/i386/i386.md (UNSPEC_CLD): New unspec volatile constant.
	(cld): New isns pattern.
	(strmov_singleop, rep_mov, strset_singleop, rep_stos, cmpstrnqi_nz_1,
	cmpstrnqi_1, strlenqi_1): Set ix86_current_function_needs_cld flag.
	* config/i386/i386.opt (mcld): New option.
	* config/i386/i386.c (ix86_expand_prologue): Emit cld insn if
	TARGET_CLD and ix86_current_function_needs_cld.
	(override_options): Use -mcld by default for 32-bit code if
	USE_IX86_CLD.

	* doc/install.texi (Options specification): Document --enable-cld.
	* doc/invoke.texi (Machine Dependent Options)
        [i386 and x86-64 Options]: Add -mcld option.
        (Intel 386 and AMD x86-64 Options): Document -mcld option.

From-SVN: r135792