OpenMP: Add OMP_STRUCTURED_BLOCK and GIMPLE_OMP_STRUCTURED_BLOCK.

In order to detect invalid jumps in and out of intervening code in
imperfectly-nested loops, the front ends need to insert some sort of
marker to identify the structured block sequences that they push into
the inner body of the loop.  The error checking happens in the
diagnose_omp_blocks pass, between gimplification and OMP lowering, so
we need both GENERIC and GIMPLE representations of these markers.
They are removed in OMP lowering so no subsequent passes need to know
about them.

This patch doesn't include any front-end changes to generate the new
data structures.

gcc/cp/ChangeLog
	* constexpr.cc (cxx_eval_constant_expression): Handle
	OMP_STRUCTURED_BLOCK.
	* pt.cc (tsubst_expr): Likewise.

gcc/ChangeLog
	* doc/generic.texi (OpenMP): Document OMP_STRUCTURED_BLOCK.
	* doc/gimple.texi (GIMPLE instruction set): Add
	GIMPLE_OMP_STRUCTURED_BLOCK.
	(GIMPLE_OMP_STRUCTURED_BLOCK): New subsection.
	* gimple-low.cc (lower_stmt): Error on GIMPLE_OMP_STRUCTURED_BLOCK.
	* gimple-pretty-print.cc (dump_gimple_omp_block): Handle
	GIMPLE_OMP_STRUCTURED_BLOCK.
	(pp_gimple_stmt_1): Likewise.
	* gimple-walk.cc (walk_gimple_stmt): Likewise.
	* gimple.cc (gimple_build_omp_structured_block): New.
	* gimple.def (GIMPLE_OMP_STRUCTURED_BLOCK): New.
	* gimple.h (gimple_build_omp_structured_block): Declare.
	(gimple_has_substatements): Handle GIMPLE_OMP_STRUCTURED_BLOCK.
	(CASE_GIMPLE_OMP): Likewise.
	* gimplify.cc (is_gimple_stmt): Handle OMP_STRUCTURED_BLOCK.
	(gimplify_expr): Likewise.
	* omp-expand.cc (GIMPLE_OMP_STRUCTURED_BLOCK): Error on
	GIMPLE_OMP_STRUCTURED_BLOCK.
	* omp-low.cc (scan_omp_1_stmt): Handle GIMPLE_OMP_STRUCTURED_BLOCK.
	(lower_omp_1): Likewise.
	(diagnose_sb_1): Likewise.
	(diagnose_sb_2): Likewise.
	* tree-inline.cc (remap_gimple_stmt): Handle
	GIMPLE_OMP_STRUCTURED_BLOCK.
	(estimate_num_insns): Likewise.
	* tree-nested.cc (convert_nonlocal_reference_stmt): Likewise.
	(convert_local_reference_stmt): Likewise.
	(convert_gimple_call): Likewise.
	* tree-pretty-print.cc (dump_generic_node): Handle
	OMP_STRUCTURED_BLOCK.
	* tree.def (OMP_STRUCTURED_BLOCK): New.
	* tree.h (OMP_STRUCTURED_BLOCK_BODY): New.

18 files changed, 114 insertions, 1 deletions

diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index da2c311..8bd5c4a 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -8155,6 +8155,7 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
     case OMP_SCAN:
     case OMP_SCOPE:
     case OMP_SECTION:
+    case OMP_STRUCTURED_BLOCK:
     case OMP_MASTER:
     case OMP_MASKED:
     case OMP_TASKGROUP:
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index c017591..2223594 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -19747,6 +19747,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
       break;
 
     case OMP_MASTER:
+    case OMP_STRUCTURED_BLOCK:
       omp_parallel_combined_clauses = NULL;
       /* FALLTHRU */
     case OMP_SECTION:
diff --git a/gcc/doc/generic.texi b/gcc/doc/generic.texi
index 3f9bddd..c8d6ef0 100644
--- a/gcc/doc/generic.texi
+++ b/gcc/doc/generic.texi
@@ -2488,6 +2488,20 @@ In some cases, @code{OMP_CONTINUE} is placed right before
 occur right after the looping body, it will be emitted between
 @code{OMP_CONTINUE} and @code{OMP_RETURN}.
 
+@item OMP_STRUCTURED_BLOCK
+
+This is another statement that doesn't correspond to an OpenMP directive.
+It is used to mark sections of code in another directive that must
+be structured block sequences, in particular for sequences of intervening code
+in the body of an @code{OMP_FOR}.  It is not necessary to use this when the
+entire body of a directive is required to be a structured block sequence,
+since that is implicit in the representation of the corresponding node.
+
+This tree node is used only to allow error checking transfers of control
+in/out of the structured block sequence after gimplification.
+It has a single operand (@code{OMP_STRUCTURED_BLOCK_BODY}) that is
+the code within the structured block sequence.
+
 @item OMP_ATOMIC
 
 Represents @code{#pragma omp atomic}.
diff --git a/gcc/doc/gimple.texi b/gcc/doc/gimple.texi
index 322c760..a3ade15 100644
--- a/gcc/doc/gimple.texi
+++ b/gcc/doc/gimple.texi
@@ -468,6 +468,7 @@ The following table briefly describes the GIMPLE instruction set.
 @item @code{GIMPLE_OMP_SECTIONS_SWITCH}	@tab x			@tab x
 @item @code{GIMPLE_OMP_SINGLE}		@tab x			@tab x
 @item @code{GIMPLE_PHI}			@tab 			@tab x
+@item @code{GIMPLE_OMP_STRUCTURED_BLOCK} @tab x			@tab
 @item @code{GIMPLE_RESX}		@tab			@tab x
 @item @code{GIMPLE_RETURN}		@tab x			@tab x
 @item @code{GIMPLE_SWITCH}		@tab x			@tab x
@@ -1040,6 +1041,7 @@ Return a deep copy of statement @code{STMT}.
 * @code{GIMPLE_OMP_SECTION}::
 * @code{GIMPLE_OMP_SECTIONS}::
 * @code{GIMPLE_OMP_SINGLE}::
+* @code{GIMPLE_OMP_STRUCTURED_BLOCK}::
 * @code{GIMPLE_PHI}::
 * @code{GIMPLE_RESX}::
 * @code{GIMPLE_RETURN}::
@@ -2160,6 +2162,23 @@ Set @code{CLAUSES} to be the clauses associated with @code{OMP_SINGLE} @code{G}.
 @end deftypefn
 
 
+@node @code{GIMPLE_OMP_STRUCTURED_BLOCK}
+@subsection @code{GIMPLE_OMP_STRUCTURED_BLOCK}
+@cindex @code{GIMPLE_OMP_STRUCTURED_BLOCK}
+
+Like the GENERIC equivalent @code{OMP_STRUCTURED_BLOCK}, this GIMPLE
+statement does not correspond directly to an OpenMP directive, and
+exists only to permit error checking of transfers of control
+in/out of structured block sequences (the @code{diagnose_omp_blocks} pass
+in @file{omp-low.cc}).  All @code{GIMPLE_OMP_STRUCTURED_BLOCK}
+nodes are eliminated during OpenMP lowering.
+
+@deftypefn {GIMPLE function} gimple gimple_build_omp_structured_block (gimple_seq body)
+Build a @code{GIMPLE_OMP_STRUCTURED_BLOCK} statement.
+@code{BODY} is the sequence of statements in the structured block sequence.
+@end deftypefn
+
+
 @node @code{GIMPLE_PHI}
 @subsection @code{GIMPLE_PHI}
 @cindex @code{GIMPLE_PHI}
diff --git a/gcc/gimple-low.cc b/gcc/gimple-low.cc
index e6f04f2..6abc286 100644
--- a/gcc/gimple-low.cc
+++ b/gcc/gimple-low.cc
@@ -717,6 +717,10 @@ lower_stmt (gimple_stmt_iterator *gsi, struct lower_data *data)
 	gsi_next (gsi);
       return;
 
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
+      /* These are supposed to be removed already in OMP lowering.  */
+      gcc_unreachable ();
+
     case GIMPLE_NOP:
     case GIMPLE_ASM:
     case GIMPLE_ASSIGN:
diff --git a/gcc/gimple-pretty-print.cc b/gcc/gimple-pretty-print.cc
index 8db221f..82017b9 100644
--- a/gcc/gimple-pretty-print.cc
+++ b/gcc/gimple-pretty-print.cc
@@ -1896,7 +1896,7 @@ dump_gimple_omp_sections (pretty_printer *buffer, const gomp_sections *gs,
     }
 }
 
-/* Dump a GIMPLE_OMP_{MASTER,ORDERED,SECTION} tuple on the
+/* Dump a GIMPLE_OMP_{MASTER,ORDERED,SECTION,STRUCTURED_BLOCK} tuple on the
    pretty_printer BUFFER.  */
 
 static void
@@ -1916,6 +1916,9 @@ dump_gimple_omp_block (pretty_printer *buffer, const gimple *gs, int spc,
 	case GIMPLE_OMP_SECTION:
 	  pp_string (buffer, "#pragma omp section");
 	  break;
+	case GIMPLE_OMP_STRUCTURED_BLOCK:
+	  pp_string (buffer, "#pragma omp __structured_block");
+	  break;
 	default:
 	  gcc_unreachable ();
 	}
@@ -2801,6 +2804,7 @@ pp_gimple_stmt_1 (pretty_printer *buffer, const gimple *gs, int spc,
 
     case GIMPLE_OMP_MASTER:
     case GIMPLE_OMP_SECTION:
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
       dump_gimple_omp_block (buffer, gs, spc, flags);
       break;
 
diff --git a/gcc/gimple-walk.cc b/gcc/gimple-walk.cc
index a019515..9516d61 100644
--- a/gcc/gimple-walk.cc
+++ b/gcc/gimple-walk.cc
@@ -693,6 +693,7 @@ walk_gimple_stmt (gimple_stmt_iterator *gsi, walk_stmt_fn callback_stmt,
     case GIMPLE_OMP_ORDERED:
     case GIMPLE_OMP_SCAN:
     case GIMPLE_OMP_SECTION:
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
     case GIMPLE_OMP_PARALLEL:
     case GIMPLE_OMP_TASK:
     case GIMPLE_OMP_SCOPE:
diff --git a/gcc/gimple.cc b/gcc/gimple.cc
index f3b941e..d5a4f63 100644
--- a/gcc/gimple.cc
+++ b/gcc/gimple.cc
@@ -1038,6 +1038,21 @@ gimple_build_omp_section (gimple_seq body)
 }
 
 
+/* Build a GIMPLE_OMP_STRUCTURED_BLOCK statement.
+
+   BODY is the structured block sequence.  */
+
+gimple *
+gimple_build_omp_structured_block (gimple_seq body)
+{
+  gimple *p = gimple_alloc (GIMPLE_OMP_STRUCTURED_BLOCK, 0);
+  if (body)
+    gimple_omp_set_body (p, body);
+
+  return p;
+}
+
+
 /* Build a GIMPLE_OMP_MASTER statement.
 
    BODY is the sequence of statements to be executed by just the master.  */
diff --git a/gcc/gimple.def b/gcc/gimple.def
index 274350d..b164a8b 100644
--- a/gcc/gimple.def
+++ b/gcc/gimple.def
@@ -275,6 +275,11 @@ DEFGSCODE(GIMPLE_OMP_CRITICAL, "gimple_omp_critical", GSS_OMP_CRITICAL)
    unspecified by the standards.  */
 DEFGSCODE(GIMPLE_OMP_FOR, "gimple_omp_for", GSS_OMP_FOR)
 
+/* GIMPLE_STRUCTURED_BLOCK <BODY> is an internal construct used to assert
+   that BODY is a structured block sequence, with no other semantics.  It is
+   used to allow error-checking of intervening code in OMP_FOR constructs.  */
+DEFGSCODE(GIMPLE_OMP_STRUCTURED_BLOCK, "gimple_omp_structured_block", GSS_OMP)
+
 /* GIMPLE_OMP_MASTER <BODY> represents #pragma omp master.
    BODY is the sequence of statements to execute in the master section.  */
 DEFGSCODE(GIMPLE_OMP_MASTER, "gimple_omp_master", GSS_OMP)
diff --git a/gcc/gimple.h b/gcc/gimple.h
index d3750f9..2d0ac10 100644
--- a/gcc/gimple.h
+++ b/gcc/gimple.h
@@ -1591,6 +1591,7 @@ gomp_parallel *gimple_build_omp_parallel (gimple_seq, tree, tree, tree);
 gomp_task *gimple_build_omp_task (gimple_seq, tree, tree, 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_master (gimple_seq);
 gimple *gimple_build_omp_masked (gimple_seq, tree);
@@ -1879,6 +1880,7 @@ gimple_has_substatements (gimple *g)
     case GIMPLE_OMP_TASKGROUP:
     case GIMPLE_OMP_ORDERED:
     case GIMPLE_OMP_SECTION:
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
     case GIMPLE_OMP_PARALLEL:
     case GIMPLE_OMP_TASK:
     case GIMPLE_OMP_SCOPE:
@@ -6746,6 +6748,7 @@ gimple_return_set_retval (greturn *gs, tree retval)
     case GIMPLE_OMP_TEAMS:			\
     case GIMPLE_OMP_SCOPE:			\
     case GIMPLE_OMP_SECTION:			\
+    case GIMPLE_OMP_STRUCTURED_BLOCK:		\
     case GIMPLE_OMP_MASTER:			\
     case GIMPLE_OMP_MASKED:			\
     case GIMPLE_OMP_TASKGROUP:			\
diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index 1e90daa..a49b50b 100644
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -5980,6 +5980,7 @@ is_gimple_stmt (tree t)
     case OMP_SCOPE:
     case OMP_SECTIONS:
     case OMP_SECTION:
+    case OMP_STRUCTURED_BLOCK:
     case OMP_SINGLE:
     case OMP_MASTER:
     case OMP_MASKED:
@@ -17037,6 +17038,7 @@ gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 	  break;
 
 	case OMP_SECTION:
+	case OMP_STRUCTURED_BLOCK:
 	case OMP_MASTER:
 	case OMP_MASKED:
 	case OMP_ORDERED:
@@ -17055,6 +17057,9 @@ gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 	      case OMP_SECTION:
 	        g = gimple_build_omp_section (body);
 	        break;
+	      case OMP_STRUCTURED_BLOCK:
+		g = gimple_build_omp_structured_block (body);
+		break;
 	      case OMP_MASTER:
 		g = gimple_build_omp_master (body);
 		break;
@@ -17455,6 +17460,7 @@ gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 		  && code != OMP_SCAN
 		  && code != OMP_SECTIONS
 		  && code != OMP_SECTION
+		  && code != OMP_STRUCTURED_BLOCK
 		  && code != OMP_SINGLE
 		  && code != OMP_SCOPE);
     }
diff --git a/gcc/omp-expand.cc b/gcc/omp-expand.cc
index 1a4d625..6172839 100644
--- a/gcc/omp-expand.cc
+++ b/gcc/omp-expand.cc
@@ -10593,6 +10593,10 @@ expand_omp (struct omp_region *region)
 	     parent GIMPLE_OMP_SECTIONS region.  */
 	  break;
 
+	case GIMPLE_OMP_STRUCTURED_BLOCK:
+	  /* We should have gotten rid of these in gimple lowering.  */
+	  gcc_unreachable ();
+
 	case GIMPLE_OMP_SINGLE:
 	case GIMPLE_OMP_SCOPE:
 	  expand_omp_single (region);
diff --git a/gcc/omp-low.cc b/gcc/omp-low.cc
index b882df0..00e6fb0 100644
--- a/gcc/omp-low.cc
+++ b/gcc/omp-low.cc
@@ -4300,6 +4300,7 @@ scan_omp_1_stmt (gimple_stmt_iterator *gsi, bool *handled_ops_p,
 	}
       /* FALLTHRU */
     case GIMPLE_OMP_SECTION:
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
     case GIMPLE_OMP_MASTER:
     case GIMPLE_OMP_ORDERED:
     case GIMPLE_OMP_CRITICAL:
@@ -14499,6 +14500,14 @@ lower_omp_1 (gimple_stmt_iterator *gsi_p, omp_context *ctx)
       gcc_assert (ctx);
       lower_omp_single (gsi_p, ctx);
       break;
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
+      /* We have already done error checking at this point, so these nodes
+	 can be completely removed and replaced with their body.  */
+      ctx = maybe_lookup_ctx (stmt);
+      gcc_assert (ctx);
+      lower_omp (gimple_omp_body_ptr (stmt), ctx);
+      gsi_replace_with_seq (gsi_p, gimple_omp_body (stmt), true);
+      break;
     case GIMPLE_OMP_MASTER:
     case GIMPLE_OMP_MASKED:
       ctx = maybe_lookup_ctx (stmt);
@@ -14886,6 +14895,7 @@ diagnose_sb_1 (gimple_stmt_iterator *gsi_p, bool *handled_ops_p,
     case GIMPLE_OMP_SECTIONS:
     case GIMPLE_OMP_SINGLE:
     case GIMPLE_OMP_SECTION:
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
     case GIMPLE_OMP_MASTER:
     case GIMPLE_OMP_MASKED:
     case GIMPLE_OMP_ORDERED:
@@ -14949,6 +14959,7 @@ diagnose_sb_2 (gimple_stmt_iterator *gsi_p, bool *handled_ops_p,
     case GIMPLE_OMP_SECTIONS:
     case GIMPLE_OMP_SINGLE:
     case GIMPLE_OMP_SECTION:
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
     case GIMPLE_OMP_MASTER:
     case GIMPLE_OMP_MASKED:
     case GIMPLE_OMP_ORDERED:
diff --git a/gcc/tree-inline.cc b/gcc/tree-inline.cc
index 1d98d96..d63060c 100644
--- a/gcc/tree-inline.cc
+++ b/gcc/tree-inline.cc
@@ -1708,6 +1708,11 @@ remap_gimple_stmt (gimple *stmt, copy_body_data *id)
 	           (s1, gimple_omp_sections_clauses (stmt));
 	  break;
 
+	case GIMPLE_OMP_STRUCTURED_BLOCK:
+	  s1 = remap_gimple_seq (gimple_omp_body (stmt), id);
+	  copy = gimple_build_omp_structured_block (s1);
+	  break;
+
 	case GIMPLE_OMP_SINGLE:
 	  s1 = remap_gimple_seq (gimple_omp_body (stmt), id);
 	  copy = gimple_build_omp_single
@@ -4562,6 +4567,7 @@ estimate_num_insns (gimple *stmt, eni_weights *weights)
     case GIMPLE_OMP_SCAN:
     case GIMPLE_OMP_SECTION:
     case GIMPLE_OMP_SECTIONS:
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
     case GIMPLE_OMP_SINGLE:
     case GIMPLE_OMP_TARGET:
     case GIMPLE_OMP_TEAMS:
diff --git a/gcc/tree-nested.cc b/gcc/tree-nested.cc
index ae7d1f1..31c7b60 100644
--- a/gcc/tree-nested.cc
+++ b/gcc/tree-nested.cc
@@ -1795,6 +1795,7 @@ convert_nonlocal_reference_stmt (gimple_stmt_iterator *gsi, bool *handled_ops_p,
       break;
 
     case GIMPLE_OMP_SECTION:
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
     case GIMPLE_OMP_MASTER:
     case GIMPLE_OMP_MASKED:
     case GIMPLE_OMP_ORDERED:
@@ -2540,6 +2541,7 @@ convert_local_reference_stmt (gimple_stmt_iterator *gsi, bool *handled_ops_p,
       break;
 
     case GIMPLE_OMP_SECTION:
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
     case GIMPLE_OMP_MASTER:
     case GIMPLE_OMP_MASKED:
     case GIMPLE_OMP_ORDERED:
@@ -3050,6 +3052,7 @@ convert_gimple_call (gimple_stmt_iterator *gsi, bool *handled_ops_p,
       /* FALLTHRU */
     case GIMPLE_OMP_SECTIONS:
     case GIMPLE_OMP_SECTION:
+    case GIMPLE_OMP_STRUCTURED_BLOCK:
     case GIMPLE_OMP_SINGLE:
     case GIMPLE_OMP_SCOPE:
     case GIMPLE_OMP_MASTER:
diff --git a/gcc/tree-pretty-print.cc b/gcc/tree-pretty-print.cc
index e6fbf94..4491176 100644
--- a/gcc/tree-pretty-print.cc
+++ b/gcc/tree-pretty-print.cc
@@ -3748,6 +3748,10 @@ dump_generic_node (pretty_printer *pp, tree node, int spc, dump_flags_t flags,
       pp_string (pp, "#pragma omp section");
       goto dump_omp_body;
 
+    case OMP_STRUCTURED_BLOCK:
+      pp_string (pp, "#pragma omp __structured_block");
+      goto dump_omp_body;
+
     case OMP_SCAN:
       if (OMP_SCAN_CLAUSES (node))
 	{
diff --git a/gcc/tree.def b/gcc/tree.def
index be94b7e..abba3d7 100644
--- a/gcc/tree.def
+++ b/gcc/tree.def
@@ -1287,6 +1287,15 @@ DEFTREECODE (OMP_SCAN, "omp_scan", tcc_statement, 2)
    Operand 0: OMP_SECTION_BODY: Section body.  */
 DEFTREECODE (OMP_SECTION, "omp_section", tcc_statement, 1)
 
+/* OpenMP structured block sequences that don't correspond to the body
+   another directive.  This is used for code fragments within the body
+   of a directive that are separately required to be structured block
+   sequence; in particular, for intervening code sequences in
+   imperfectly-nested loops.
+   Operand 0: BODY: contains the statement(s) within the structured block
+   sequence.  */
+DEFTREECODE (OMP_STRUCTURED_BLOCK, "omp_structured_block", tcc_statement, 1)
+
 /* OpenMP - #pragma omp master
    Operand 0: OMP_MASTER_BODY: Master section body.  */
 DEFTREECODE (OMP_MASTER, "omp_master", tcc_statement, 1)
diff --git a/gcc/tree.h b/gcc/tree.h
index 4c04245..75bda3f 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -1530,6 +1530,9 @@ class auto_suppress_location_wrappers
 
 #define OMP_SECTION_BODY(NODE)	   TREE_OPERAND (OMP_SECTION_CHECK (NODE), 0)
 
+#define OMP_STRUCTURED_BLOCK_BODY(NODE) \
+  TREE_OPERAND (OMP_STRUCTURED_BLOCK_CHECK (NODE), 0)
+
 #define OMP_SINGLE_BODY(NODE)	   TREE_OPERAND (OMP_SINGLE_CHECK (NODE), 0)
 #define OMP_SINGLE_CLAUSES(NODE)   TREE_OPERAND (OMP_SINGLE_CHECK (NODE), 1)