OpenMP: middle-end support for dispatch + adjust_args

This patch adds middle-end support for the `dispatch` construct and the
`adjust_args` clause. The heavy lifting is done in `gimplify_omp_dispatch` and
`gimplify_call_expr` respectively. For `adjust_args`, this mostly consists in
emitting a call to `omp_get_mapped_ptr` for the adequate device.

For dispatch, the following steps are performed:

* Handle the device clause, if any: set the default-device ICV at the top of the
dispatch region and restore its previous value at the end.

* Handle novariants and nocontext clauses, if any. Evaluate compile-time
constants and select a variant, if possible. Otherwise, emit code to handle all
possible cases at run time.

gcc/ChangeLog:

	* builtins.cc (builtin_fnspec): Handle BUILT_IN_OMP_GET_MAPPED_PTR.
	* gimple-low.cc (lower_stmt): Handle GIMPLE_OMP_DISPATCH.
	* gimple-pretty-print.cc (dump_gimple_omp_dispatch): New function.
	(pp_gimple_stmt_1): Handle GIMPLE_OMP_DISPATCH.
	* gimple-walk.cc (walk_gimple_stmt): Likewise.
	* gimple.cc (gimple_build_omp_dispatch): New function.
	(gimple_copy): Handle GIMPLE_OMP_DISPATCH.
	* gimple.def (GIMPLE_OMP_DISPATCH): Define.
	* gimple.h (gimple_build_omp_dispatch): Declare.
	(gimple_has_substatements): Handle GIMPLE_OMP_DISPATCH.
	(gimple_omp_dispatch_clauses): New function.
	(gimple_omp_dispatch_clauses_ptr): Likewise.
	(gimple_omp_dispatch_set_clauses): Likewise.
	(gimple_return_set_retval): Handle GIMPLE_OMP_DISPATCH.
	* gimplify.cc (enum omp_region_type): Add ORT_DISPATCH.
	(struct gimplify_omp_ctx): Add in_call_args.
	(gimplify_call_expr): Handle need_device_ptr arguments.
	(is_gimple_stmt): Handle OMP_DISPATCH.
	(gimplify_scan_omp_clauses): Handle OMP_CLAUSE_DEVICE in a dispatch
	construct. Handle OMP_CLAUSE_NOVARIANTS and OMP_CLAUSE_NOCONTEXT.
	(omp_has_novariants): New function.
	(omp_has_nocontext): Likewise.
	(omp_construct_selector_matches): Handle OMP_DISPATCH with nocontext
	clause.
	(find_ifn_gomp_dispatch): New function.
	(gimplify_omp_dispatch): Likewise.
	(gimplify_expr): Handle OMP_DISPATCH.
	* gimplify.h (omp_has_novariants): Declare.
	* internal-fn.cc (expand_GOMP_DISPATCH): New function.
	* internal-fn.def (GOMP_DISPATCH): Define.
	* omp-builtins.def (BUILT_IN_OMP_GET_MAPPED_PTR): Define.
	(BUILT_IN_OMP_GET_DEFAULT_DEVICE): Define.
	(BUILT_IN_OMP_SET_DEFAULT_DEVICE): Define.
	* omp-general.cc (omp_construct_traits_to_codes): Add OMP_DISPATCH.
	(struct omp_ts_info): Add dispatch.
	(omp_resolve_declare_variant): Handle novariants. Adjust
	DECL_ASSEMBLER_NAME.
	* omp-low.cc (scan_omp_1_stmt): Handle GIMPLE_OMP_DISPATCH.
	(lower_omp_dispatch): New function.
	(lower_omp_1): Call it.
	* tree-inline.cc (remap_gimple_stmt): Handle GIMPLE_OMP_DISPATCH.
	(estimate_num_insns): Handle GIMPLE_OMP_DISPATCH.

Author: parras

gcc/builtins.cc

@@ -12583,6 +12583,8 @@ builtin_fnspec (tree callee)
 	 by its first argument.  */
       case BUILT_IN_POSIX_MEMALIGN:
 	return ".cOt";
+      case BUILT_IN_OMP_GET_MAPPED_PTR:
+	return ". R ";
 
       default:
 	return "";

gcc/gimple-low.cc

@@ -746,6 +746,7 @@ lower_stmt (gimple_stmt_iterator *gsi, struct lower_data *data)
     case GIMPLE_EH_MUST_NOT_THROW:
     case GIMPLE_OMP_FOR:
     case GIMPLE_OMP_SCOPE:
+    case GIMPLE_OMP_DISPATCH:
     case GIMPLE_OMP_SECTIONS:
     case GIMPLE_OMP_SECTIONS_SWITCH:
     case GIMPLE_OMP_SECTION:

gcc/gimple-pretty-print.cc

@@ -1727,6 +1727,35 @@ dump_gimple_omp_scope (pretty_printer *pp, const gimple *gs,
     }
 }
 
+/* Dump a GIMPLE_OMP_DISPATCH tuple on the pretty_printer BUFFER.  */
+
+static void
+dump_gimple_omp_dispatch (pretty_printer *buffer, const gimple *gs, int spc,
+			  dump_flags_t flags)
+{
+  if (flags & TDF_RAW)
+    {
+      dump_gimple_fmt (buffer, spc, flags, "%G <%+BODY <%S>%nCLAUSES <", gs,
+		       gimple_omp_body (gs));
+      dump_omp_clauses (buffer, gimple_omp_dispatch_clauses (gs), spc, flags);
+      dump_gimple_fmt (buffer, spc, flags, " >");
+    }
+  else
+    {
+      pp_string (buffer, "#pragma omp dispatch");
+      dump_omp_clauses (buffer, gimple_omp_dispatch_clauses (gs), spc, flags);
+      if (!gimple_seq_empty_p (gimple_omp_body (gs)))
+	{
+	  newline_and_indent (buffer, spc + 2);
+	  pp_left_brace (buffer);
+	  pp_newline (buffer);
+	  dump_gimple_seq (buffer, gimple_omp_body (gs), spc + 4, flags);
+	  newline_and_indent (buffer, spc + 2);
+	  pp_right_brace (buffer);
+	}
+    }
+}
+
 /* Dump a GIMPLE_OMP_TARGET tuple on the pretty_printer PP.  */
 
 static void
@@ -2806,6 +2835,10 @@ pp_gimple_stmt_1 (pretty_printer *pp, const gimple *gs, int spc,
       dump_gimple_omp_scope (pp, gs, spc, flags);
       break;
 
+    case GIMPLE_OMP_DISPATCH:
+      dump_gimple_omp_dispatch(pp, gs, spc, flags);
+      break;
+
     case GIMPLE_OMP_MASTER:
     case GIMPLE_OMP_SECTION:
     case GIMPLE_OMP_STRUCTURED_BLOCK:

gcc/gimple-walk.cc

@@ -707,6 +707,7 @@ walk_gimple_stmt (gimple_stmt_iterator *gsi, walk_stmt_fn callback_stmt,
     case GIMPLE_OMP_PARALLEL:
     case GIMPLE_OMP_TASK:
     case GIMPLE_OMP_SCOPE:
+    case GIMPLE_OMP_DISPATCH:
     case GIMPLE_OMP_SECTIONS:
     case GIMPLE_OMP_SINGLE:
     case GIMPLE_OMP_TARGET:

gcc/gimple.cc

@@ -1239,6 +1239,21 @@ gimple_build_omp_scope (gimple_seq body, tree clauses)
   return p;
 }
 
+/* Build a GIMPLE_OMP_DISPATCH statement.
+
+   BODY is the target function call to be dispatched.
+   CLAUSES are any of the OMP dispatch construct's clauses.  */
+
+gimple *
+gimple_build_omp_dispatch (gimple_seq body, tree clauses)
+{
+  gimple *p = gimple_alloc (GIMPLE_OMP_DISPATCH, 0);
+  gimple_omp_dispatch_set_clauses (p, clauses);
+  if (body)
+    gimple_omp_set_body (p, body);
+
+  return p;
+}
 
 /* Build a GIMPLE_OMP_TARGET statement.
 
@@ -2152,6 +2167,11 @@ gimple_copy (gimple *stmt)
 	  gimple_omp_scope_set_clauses (copy, t);
 	  goto copy_omp_body;
 
+	case GIMPLE_OMP_DISPATCH:
+	  t = unshare_expr (gimple_omp_dispatch_clauses (stmt));
+	  gimple_omp_dispatch_set_clauses (copy, t);
+	  goto copy_omp_body;
+
 	case GIMPLE_OMP_TARGET:
 	  {
 	    gomp_target *omp_target_stmt = as_a <gomp_target *> (stmt);

gcc/gimple.def

@@ -350,6 +350,11 @@ DEFGSCODE(GIMPLE_OMP_SCAN, "gimple_omp_scan", GSS_OMP_SINGLE_LAYOUT)
    CLAUSES is an OMP_CLAUSE chain holding the associated clauses.  */
 DEFGSCODE(GIMPLE_OMP_SCOPE, "gimple_omp_scope", GSS_OMP_SINGLE_LAYOUT)
 
+/* GIMPLE_OMP_DISPATCH <BODY, CLAUSES> represents #pragma omp dispatch
+   BODY is the target function call to be dispatched.
+   CLAUSES is an OMP_CLAUSE chain holding the associated clauses.  */
+DEFGSCODE(GIMPLE_OMP_DISPATCH, "gimple_omp_dispatch", GSS_OMP_SINGLE_LAYOUT)
+
 /* OMP_SECTION <BODY> represents #pragma omp section.
    BODY is the sequence of statements in the section body.  */
 DEFGSCODE(GIMPLE_OMP_SECTION, "gimple_omp_section", GSS_OMP)

gcc/gimple.h

@@ -742,7 +742,7 @@ struct GTY((tag("GSS_OMP_CONTINUE")))
 };
 
 /* GIMPLE_OMP_SINGLE, GIMPLE_OMP_ORDERED, GIMPLE_OMP_TASKGROUP,
-   GIMPLE_OMP_SCAN, GIMPLE_OMP_MASKED, GIMPLE_OMP_SCOPE.  */
+   GIMPLE_OMP_SCAN, GIMPLE_OMP_MASKED, GIMPLE_OMP_SCOPE, GIMPLE_OMP_DISPATCH. */
 
 struct GTY((tag("GSS_OMP_SINGLE_LAYOUT")))
   gimple_statement_omp_single_layout : public gimple_statement_omp
@@ -1591,6 +1591,7 @@ gomp_task *gimple_build_omp_task (gimple_seq, tree, tree, tree, tree,
 gimple *gimple_build_omp_section (gimple_seq);
 gimple *gimple_build_omp_structured_block (gimple_seq);
 gimple *gimple_build_omp_scope (gimple_seq, tree);
+gimple *gimple_build_omp_dispatch (gimple_seq, tree);
 gimple *gimple_build_omp_master (gimple_seq);
 gimple *gimple_build_omp_masked (gimple_seq, tree);
 gimple *gimple_build_omp_taskgroup (gimple_seq, tree);
@@ -1882,6 +1883,7 @@ gimple_has_substatements (gimple *g)
     case GIMPLE_OMP_PARALLEL:
     case GIMPLE_OMP_TASK:
     case GIMPLE_OMP_SCOPE:
+    case GIMPLE_OMP_DISPATCH:
     case GIMPLE_OMP_SECTIONS:
     case GIMPLE_OMP_SINGLE:
     case GIMPLE_OMP_TARGET:
@@ -5434,6 +5436,34 @@ gimple_omp_scope_set_clauses (gimple *gs, tree clauses)
     = clauses;
 }
 
+/* Return the clauses associated with OMP_DISPATCH statement GS.  */
+
+inline tree
+gimple_omp_dispatch_clauses (const gimple *gs)
+{
+  GIMPLE_CHECK (gs, GIMPLE_OMP_DISPATCH);
+  return static_cast<const gimple_statement_omp_single_layout *> (gs)->clauses;
+}
+
+/* Return a pointer to the clauses associated with OMP dispatch statement
+   GS.  */
+
+inline tree *
+gimple_omp_dispatch_clauses_ptr (gimple *gs)
+{
+  GIMPLE_CHECK (gs, GIMPLE_OMP_DISPATCH);
+  return &static_cast<gimple_statement_omp_single_layout *> (gs)->clauses;
+}
+
+/* Set CLAUSES to be the clauses associated with OMP dispatch statement
+   GS.  */
+
+inline void
+gimple_omp_dispatch_set_clauses (gimple *gs, tree clauses)
+{
+  GIMPLE_CHECK (gs, GIMPLE_OMP_DISPATCH);
+  static_cast<gimple_statement_omp_single_layout *> (gs)->clauses = clauses;
+}
 
 /* Return the kind of the OMP_FOR statemement G.  */
 
@@ -6768,6 +6798,7 @@ gimple_return_set_retval (greturn *gs, tree retval)
     case GIMPLE_OMP_TARGET:			\
     case GIMPLE_OMP_TEAMS:			\
     case GIMPLE_OMP_SCOPE:			\
+    case GIMPLE_OMP_DISPATCH:			\
     case GIMPLE_OMP_SECTION:			\
     case GIMPLE_OMP_STRUCTURED_BLOCK:		\
     case GIMPLE_OMP_MASTER:			\