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.

gcc/ChangeLog:

	* 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.
	* omp-simd-clone.cc (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.
	* opts.cc (default_options_table): Add -fopenmp-target-simd-clone.
	* target.def (TARGET_SIMD_CLONE_COMPUTE_VECSIZE_AND_SIMDLEN):
	Add bool explicit_p argument.
	* doc/tm.texi: Regenerated.
	* config/aarch64/aarch64.cc
	(aarch64_simd_clone_compute_vecsize_and_simdlen): Update.
	* config/gcn/gcn.cc
	(gcn_simd_clone_compute_vecsize_and_simdlen): Update.
	* config/i386/i386.cc
	(ix86_simd_clone_compute_vecsize_and_simdlen): Update.

gcc/testsuite/ChangeLog:

	* 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.

libgomp/ChangeLog:

	* 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.

2 files changed, 23 insertions, 2 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 202388b..e312b5c 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -204,7 +204,7 @@ in the following sections.
 -flax-vector-conversions  -fms-extensions @gol
 -foffload=@var{arg}  -foffload-options=@var{arg} @gol
 -fopenacc  -fopenacc-dim=@var{geom} @gol
--fopenmp  -fopenmp-simd @gol
+-fopenmp  -fopenmp-simd  -fopenmp-target-simd-clone@r{[}=@var{device-type}@r{]} @gol
 -fpermitted-flt-eval-methods=@var{standard} @gol
 -fplan9-extensions  -fsigned-bitfields  -funsigned-bitfields @gol
 -fsigned-char  -funsigned-char -fstrict-flex-arrays[=@var{n}] @gol
@@ -2743,6 +2743,27 @@ Enable handling of OpenMP's @code{simd}, @code{declare simd},
 @code{[[omp::directive(...)]]} and @code{[[omp::sequence(...)]]} in C++
 and @code{!$omp} in Fortran.  Other OpenMP directives are ignored.
 
+@item -fopenmp-target-simd-clone
+@item -fopenmp-target-simd-clone=@var{device-type}
+@opindex fopenmp-target-simd-clone
+@cindex OpenMP target SIMD clone
+In addition to generating SIMD clones for functions marked with the
+@code{declare simd} directive, GCC also generates clones
+for functions marked with the OpenMP @code{declare target} directive
+that are suitable for vectorization when this option is in effect.  The
+@var{device-type} may be one of @code{none}, @code{host}, @code{nohost},
+and @code{any}, which correspond to keywords for the @code{device_type}
+clause of the @code{declare target} directive; clones are generated for
+the intersection of devices specified.
+@option{-fopenmp-target-simd-clone} is equivalent to
+@option{-fopenmp-target-simd-clone=any} and
+@option{-fno-openmp-target-simd-clone} is equivalent to
+@option{-fopenmp-target-simd-clone=none}.
+
+At @option{-O2} and higher (but not @option{-Os} or @option{-Og}) this
+optimization defaults to @option{-fopenmp-target-simd-clone=nohost}; otherwise
+it is disabled by default.
+
 @item -fpermitted-flt-eval-methods=@var{style}
 @opindex fpermitted-flt-eval-methods
 @opindex fpermitted-flt-eval-methods=c11
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index af77d16..8fe49c2 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -6290,7 +6290,7 @@ The default is @code{NULL_TREE} which means to not vectorize scatter
 stores.
 @end deftypefn
 
-@deftypefn {Target Hook} int TARGET_SIMD_CLONE_COMPUTE_VECSIZE_AND_SIMDLEN (struct cgraph_node *@var{}, struct cgraph_simd_clone *@var{}, @var{tree}, @var{int})
+@deftypefn {Target Hook} int TARGET_SIMD_CLONE_COMPUTE_VECSIZE_AND_SIMDLEN (struct cgraph_node *@var{}, struct cgraph_simd_clone *@var{}, @var{tree}, @var{int}, @var{bool})
 This hook should set @var{vecsize_mangle}, @var{vecsize_int}, @var{vecsize_float}
 fields in @var{simd_clone} structure pointed by @var{clone_info} argument and also
 @var{simdlen} field if it was previously 0.