nvptx backend prerequisites for OpenMP offloading

gcc/
	* config/nvptx/mkoffload.c (main): Check that either OpenACC or OpenMP
	is selected.  Pass -mgomp to offload compiler in OpenMP case.
	* config/nvptx/nvptx-protos.h (nvptx_shuffle_kind): Move enum
	declaration from nvptx.c.
	(nvptx_gen_shuffle): Declare.
	(nvptx_output_set_softstack): Declare.
	* config/nvptx/nvptx.c (nvptx_shuffle_kind): Move to nvptx-protos.h.
	(need_softstack_decl): New variable.
	(need_unisimt_decl): New variable.
	(diagnose_openacc_conflict): New.  Use it...
	(nvptx_option_override): ...here.  Handle TARGET_GOMP.
	(nvptx_encode_section_info): Handle "shared" attribute.
	(write_as_kernel): Restrict to OpenACC target regions.
	(init_softstack_frame): New.
	(nvptx_init_unisimt_predicate): New.
	(write_omp_entry): New.  Use it...
	(nvptx_declare_function_name): ...here to emit OpenMP target region
	entrypoints.  Handle TARGET_SOFT_STACK.  Call
	nvptx_init_unisimt_predicate.
	(nvptx_output_set_softstack): New.
	(nvptx_get_drap_rtx): Return %argp as the DRAP if needed.
	(nvptx_gen_shuffle): Export.
	(nvptx_output_call_insn): Handle COND_EXEC patterns.  Emit instruction
	predicate.
	(nvptx_print_operand): Fix handling of instruction predicates.
	(nvptx_get_unisimt_master): New helper function.
	(nvptx_get_unisimt_predicate): Ditto.
	(nvptx_call_insn_is_syscall_p): Ditto.
	(nvptx_unisimt_handle_set): Ditto.
	(nvptx_reorg_uniform_simt): New.  Transform code for -muniform-simt.
	(nvptx_reorg): Call nvptx_reorg_uniform_simt.
	(nvptx_handle_shared_attribute): New.  Use it...
	(nvptx_attribute_table): ... here (new entry).
	(nvptx_record_offload_symbol): Handle NULL attributes.
	(nvptx_file_end): Handle need_softstack_decl and need_unisimt_decl.
	(nvptx_simt_vf): New.
	(TARGET_SIMT_VF): Define.
	* config/nvptx/nvptx.h (TARGET_CPU_CPP_BUILTINS): Define
	__nvptx_softstack or __nvptx_unisimt__ when -msoft-stack, or resp.
	-muniform-simt option is active.
	(STACK_SIZE_MODE): Define.
	(FIXED_REGISTERS): Adjust.
	(SOFTSTACK_SLOT_REGNUM): New.
	(SOFTSTACK_PREV_REGNUM): New.
	(REGISTER_NAMES): Adjust.
	(struct machine_function): New fields.
	* config/nvptx/nvptx.md (UNSPEC_SET_SOFTSTACK): New.
	(UNSPEC_VOTE_BALLOT): Ditto.
	(UNSPEC_LANEID): Ditto.
	(UNSPECV_NOUNROLL): Ditto.
	(atomic): New attribute.
	(predicable): New attribute.  Generate predicated forms via
	define_cond_exec.
	(br_true): Mark as not predicable.
	(br_false): Ditto.
	(br_true_uni): Ditto.
	(br_false_uni): Ditto.
	(return): Ditto.
	(trap_if_true): Ditto.
	(trap_if_false): Ditto.
	(nvptx_fork): Ditto.
	(nvptx_forked): Ditto.
	(nvptx_joining): Ditto.
	(nvptx_join): Ditto.
	(nvptx_barsync): Ditto.
	(epilogue): Emit stack restore if TARGET_SOFT_STACK.
	(allocate_stack): Implement for TARGET_SOFT_STACK.  Remove unused code.
	(allocate_stack_<mode>): Remove unused pattern.
	(set_softstack_insn): New pattern.
	(restore_stack_block): Handle for TARGET_SOFT_STACK.
	(nvptx_vote_ballot): New pattern.
	(omp_simt_lane): Ditto.
	(omp_simt_last_lane): Ditto.
	(omp_simt_ordered): Ditto.
	(omp_simt_vote_any): Ditto.
	(omp_simt_xchg_bfly): Ditto.
	(omp_simt_xchg_idx): Ditto.
	(nvptx_nounroll): Ditto.
	(atomic_compare_and_swap<mode>_1): Mark with atomic attribute.
	(atomic_exchange<mode>): Ditto.
	(atomic_fetch_add<mode>): Ditto.
	(atomic_fetch_addsf): Ditto.
	(atomic_fetch_<logic><mode>): Ditto.
	* config/nvptx/nvptx.opt: (msoft-stack): New option.
	(muniform-simt): Ditto.
	(mgomp): Ditto.
	* config/nvptx/t-nvptx (MULTILIB_OPTIONS): New.
	* doc/extend.texi (Nvidia PTX Variable Attributes): New section.
	* doc/invoke.texi (msoft-stack): Document.
	(muniform-simt): Document
	(mgomp): Document.
	* doc/tm.texi: Regenerate.
	* doc/tm.texi.in: (TARGET_SIMT_VF): New hook.
	* target.def: Define it.
	* target-insns.def (omp_simt_lane): New.
	(omp_simt_last_lane): New.
	(omp_simt_ordered): New.
	(omp_simt_vote_any): New.
	(omp_simt_xchg_bfly): New.
	(omp_simt_xchg_idx): New.

libgcc/
	* config/nvptx/crt0.c (__main): Setup __nvptx_stacks and __nvptx_uni.
	* config/nvptx/mgomp.c: New file.
	* config/nvptx/t-nvptx: Add mgomp.c

gcc/testsuite/
	* lib/target-supports.exp (check_effective_target_alloca): Use a
	compile test.
	* gcc.target/nvptx/softstack.c: New test.
	* gcc.target/nvptx/decl-shared.c: New test.
	* gcc.target/nvptx/decl-shared-init.c: New test.

From-SVN: r242503

4 files changed, 52 insertions, 0 deletions

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 0669f79..4dcc7f6 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -5576,6 +5576,7 @@ attributes.
 * MeP Variable Attributes::
 * Microsoft Windows Variable Attributes::
 * MSP430 Variable Attributes::
+* Nvidia PTX Variable Attributes::
 * PowerPC Variable Attributes::
 * RL78 Variable Attributes::
 * SPU Variable Attributes::
@@ -6257,6 +6258,20 @@ same name (@pxref{MSP430 Function Attributes}).
 These attributes can be applied to both functions and variables.
 @end table
 
+@node Nvidia PTX Variable Attributes
+@subsection Nvidia PTX Variable Attributes
+
+These variable attributes are supported by the Nvidia PTX back end:
+
+@table @code
+@item shared
+@cindex @code{shared} attribute, Nvidia PTX
+Use this attribute to place a variable in the @code{.shared} memory space.
+This memory space is private to each cooperative thread array; only threads
+within one thread block refer to the same instance of the variable.
+The runtime does not initialize variables in this memory space.
+@end table
+
 @node PowerPC Variable Attributes
 @subsection PowerPC Variable Attributes
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 1d24b31..620225c 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -20570,6 +20570,37 @@ offloading execution.
 Apply partitioned execution optimizations.  This is the default when any
 level of optimization is selected.
 
+@item -msoft-stack
+@opindex msoft-stack
+Generate code that does not use @code{.local} memory
+directly for stack storage. Instead, a per-warp stack pointer is
+maintained explicitly. This enables variable-length stack allocation (with
+variable-length arrays or @code{alloca}), and when global memory is used for
+underlying storage, makes it possible to access automatic variables from other
+threads, or with atomic instructions. This code generation variant is used
+for OpenMP offloading, but the option is exposed on its own for the purpose
+of testing the compiler; to generate code suitable for linking into programs
+using OpenMP offloading, use option @option{-mgomp}.
+
+@item -muniform-simt
+@opindex muniform-simt
+Switch to code generation variant that allows to execute all threads in each
+warp, while maintaining memory state and side effects as if only one thread
+in each warp was active outside of OpenMP SIMD regions.  All atomic operations
+and calls to runtime (malloc, free, vprintf) are conditionally executed (iff
+current lane index equals the master lane index), and the register being
+assigned is copied via a shuffle instruction from the master lane.  Outside of
+SIMD regions lane 0 is the master; inside, each thread sees itself as the
+master.  Shared memory array @code{int __nvptx_uni[]} stores all-zeros or
+all-ones bitmasks for each warp, indicating current mode (0 outside of SIMD
+regions).  Each thread can bitwise-and the bitmask at position @code{tid.y}
+with current lane index to compute the master lane index.
+
+@item -mgomp
+@opindex mgomp
+Generate code for use in OpenMP offloading: enables @option{-msoft-stack} and
+@option{-muniform-simt} options, and selects corresponding multilib variant.
+
 @end table
 
 @node PDP-11 Options
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 85341ae..84bba07 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -5862,6 +5862,10 @@ usable.  In that case, the smaller the number is, the more desirable it is
 to use it.
 @end deftypefn
 
+@deftypefn {Target Hook} int TARGET_SIMT_VF (void)
+Return number of threads in SIMT thread group on the target.
+@end deftypefn
+
 @deftypefn {Target Hook} bool TARGET_GOACC_VALIDATE_DIMS (tree @var{decl}, int *@var{dims}, int @var{fn_level})
 This hook should check the launch dimensions provided for an OpenACC
 compute region, or routine.  Defaulted values are represented as -1
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 400d574..9afd5daa 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -4295,6 +4295,8 @@ address;  but often a machine-dependent strategy can generate better code.
 
 @hook TARGET_SIMD_CLONE_USABLE
 
+@hook TARGET_SIMT_VF
+
 @hook TARGET_GOACC_VALIDATE_DIMS
 
 @hook TARGET_GOACC_DIM_LIMIT