* common/config/i386/i386-common.c (OPTION_MASK_ISA_PREFETCHWT1_SET),
	(OPTION_MASK_ISA_PREFETCHWT1_UNSET): New.
	(ix86_handle_option): Handle OPT_mprefetchwt1.
	* config/i386/cpuid.h (bit_PREFETCHWT1): New.
	* config/i386/driver-i386.c (host_detect_local_cpu): Detect
	PREFETCHWT1 CPUID.
	* config/i386/i386-c.c (ix86_target_macros_internal): Handle
	OPTION_MASK_ISA_PREFETCHWT1.
	* config/i386/i386.c (ix86_target_string): Handle mprefetchwt1.
	(PTA_PREFETCHWT1): New.
	(ix86_option_override_internal): Handle PTA_PREFETCHWT1.
	(ix86_valid_target_attribute_inner_p): Handle OPT_mprefetchwt1.
	* config/i386/i386.h (TARGET_PREFETCHWT1), (TARGET_PREFETCHWT1_P):
	  New.
	* config/i386/i386.md (prefetch): Check TARGET_PREFETCHWT1
	(*prefetch_avx512pf_<mode>_: Change into ...
	 (*prefetch_prefetchwt1_<mode>: This.
	* config/i386/i386.opt (mprefetchwt1): New.
	* config/i386/xmmintrin.h (_mm_hint): Add _MM_HINT_ET1.
	(_mm_prefetch): Handle intent to write.
	* doc/invoke.texi (mprefetchwt1), (mno-prefetchwt1): Doccument.

gcc/testsuite/
	* gcc.target/i386/avx-1.c: Update __builtin_prefetch.
	* gcc.target/i386/prefetchwt1-1.c: New.
	* g++.dg/other/i386-2.C: Add new option.
	* g++.dg/other/i386-3.C: Ditto.
	* gcc.target/i386/sse-12.c: Ditto.
	* gcc.target/i386/sse-13.c: Update __builtin_prefetch, add new option.
	* gcc.target/i386/sse-22.c: Add new option.
	* gcc.target/i386/sse-23.c: Update __builtin_prefetch, add new option.

From-SVN: r208115