OpenMP: Generate SIMD clones for functions with "declare target"

This patch causes the IPA simdclone pass to generate clones for
functions with the "omp declare target" attribute as if they had
"omp declare simd", provided the function appears to be suitable for
SIMD execution.  The filter is conservative, rejecting functions
that write memory or that call other functions not known to be safe.
A new option -fopenmp-target-simd-clone is added to control this
transformation; it's enabled for offload processing at -O2 and higher.


	* common.opt (fopenmp-target-simd-clone): New option.
	(target_simd_clone_device): New enum to go with it.
	* doc/invoke.texi (-fopenmp-target-simd-clone): Document.
	* flag-types.h (enum omp_target_simd_clone_device_kind): New.
	* (auto_simd_fail): New function.
	(auto_simd_check_stmt): New function.
	(plausible_type_for_simd_clone): New function.
	(ok_for_auto_simd_clone): New function.
	(simd_clone_create): Add force_local argument, make the symbol
	have internal linkage if it is true.
	(expand_simd_clones): Also check for cloneable functions with
	"omp declare target".  Pass explicit_p argument to
	simd_clone.compute_vecsize_and_simdlen target hook.
	* (default_options_table): Add -fopenmp-target-simd-clone.
	Add bool explicit_p argument.
	* doc/tm.texi: Regenerated.
	* config/aarch64/
	(aarch64_simd_clone_compute_vecsize_and_simdlen): Update.
	* config/gcn/
	(gcn_simd_clone_compute_vecsize_and_simdlen): Update.
	* config/i386/
	(ix86_simd_clone_compute_vecsize_and_simdlen): Update.


	* g++.dg/gomp/target-simd-clone-1.C: New.
	* g++.dg/gomp/target-simd-clone-2.C: New.
	* gcc.dg/gomp/target-simd-clone-1.c: New.
	* gcc.dg/gomp/target-simd-clone-2.c: New.
	* gcc.dg/gomp/target-simd-clone-3.c: New.
	* gcc.dg/gomp/target-simd-clone-4.c: New.
	* gcc.dg/gomp/target-simd-clone-5.c: New.
	* gcc.dg/gomp/target-simd-clone-6.c: New.
	* gcc.dg/gomp/target-simd-clone-7.c: New.
	* gcc.dg/gomp/target-simd-clone-8.c: New.
	* lib/scanoffloadipa.exp: New.


	* testsuite/lib/libgomp.exp: Load scanoffloadipa.exp library.
	* testsuite/libgomp.c/target-simd-clone-1.c: New.
	* testsuite/libgomp.c/target-simd-clone-2.c: New.
	* testsuite/libgomp.c/target-simd-clone-3.c: New.
25 files changed