[Ada] Elaboration order v4.0 and cycle detection

This patch introduces a new cycle detection algorithm which is based on
Tarjan's "Enumeration of the Elementary Circuits of a Directed Graph"
algorithm, with several ideas borrowed from Jonson's "Finding all the
Elementary Circuits of a Directed Graph" algorithm.

No need for a test because the new algorithm improves the performance of
cycle detection only.

2019-07-10  Hristian Kirtchev  <kirtchev@adacore.com>

gcc/ada/

	* bindo.adb: Update the section on switches.
	* bindo-graphs.adb
	(Add_Cycle, Add_Vertex_And_Complement): Remove.
	(Create): The graph no longer needs a set of recorded cycles
	because the cycles are not rediscovered in permuted forms.
	(Cycle_End_Vertices): New routine.
	(Destroy): The graph no longer needs a set of recorded cycles
	because the cycles are not rediscovered in permuted forms.
	(Destroy_Library_Graph_Vertex): Move to the library level.
	(Find_All_Cycles_Through_Vertex, Find_All_Cycles_With_Edge):
	Remove.
	(Find_Cycles_From_Successor, Find_Cycles_From_Vertex,
	Find_Cycles_In_Component, Has_Elaborate_All_Edge): New routines.
	(Insert_And_Sort): Remove.
	(Is_Elaborate_Body_Edge): Use predicate
	Is_Vertex_With_Elaborate_Body.
	(Is_Recorded_Cycle): Remove.
	(Is_Vertex_With_Elaborate_Body): New routine.
	(Normalize_And_Add_Cycle): Remove.
	(Precedence): Rename to xxx_Precedence, where xxx relates to the
	input.  These versions better reflect the desired input
	precedence.
	(Record_Cycle): New routine.
	(Remove_Vertex_And_Complement, Set_Is_Recorded_Cycle): Remove.
	(Trace_xxx): Update all versions to use debug switch -d_t.
	(Trace_Component): New routine.
	(Trace_Eol): Removed.
	(Trace_Vertex): Do not output the component as this information
	is already available when the component is traced.
	(Unvisit, Visit): New routine.
	* bindo-graphs.ads: Add new instance LGV_Lists.  Remove instance
	RC_Sets.  Update the structure of type Library_Graph_Attributes
	to remove the set of recorded cycles.
	(Destroy_Library_Graph_Vertex): Move to the library level.
	* bindo-writers.adb (Write_Component_Vertices): Output
	information about the number of vertices.
	* debug.adb: Document the use of binder switch -d_t.  Update the
	use of binder switch -d_T.

From-SVN: r273330

gcc/ada/ChangeLog

+2019-07-10  Hristian Kirtchev  <kirtchev@adacore.com>
+
+	* bindo.adb: Update the section on switches.
+	* bindo-graphs.adb
+	(Add_Cycle, Add_Vertex_And_Complement): Remove.
+	(Create): The graph no longer needs a set of recorded cycles
+	because the cycles are not rediscovered in permuted forms.
+	(Cycle_End_Vertices): New routine.
+	(Destroy): The graph no longer needs a set of recorded cycles
+	because the cycles are not rediscovered in permuted forms.
+	(Destroy_Library_Graph_Vertex): Move to the library level.
+	(Find_All_Cycles_Through_Vertex, Find_All_Cycles_With_Edge):
+	Remove.
+	(Find_Cycles_From_Successor, Find_Cycles_From_Vertex,
+	Find_Cycles_In_Component, Has_Elaborate_All_Edge): New routines.
+	(Insert_And_Sort): Remove.
+	(Is_Elaborate_Body_Edge): Use predicate
+	Is_Vertex_With_Elaborate_Body.
+	(Is_Recorded_Cycle): Remove.
+	(Is_Vertex_With_Elaborate_Body): New routine.
+	(Normalize_And_Add_Cycle): Remove.
+	(Precedence): Rename to xxx_Precedence, where xxx relates to the
+	input.  These versions better reflect the desired input
+	precedence.
+	(Record_Cycle): New routine.
+	(Remove_Vertex_And_Complement, Set_Is_Recorded_Cycle): Remove.
+	(Trace_xxx): Update all versions to use debug switch -d_t.
+	(Trace_Component): New routine.
+	(Trace_Eol): Removed.
+	(Trace_Vertex): Do not output the component as this information
+	is already available when the component is traced.
+	(Unvisit, Visit): New routine.
+	* bindo-graphs.ads: Add new instance LGV_Lists.  Remove instance
+	RC_Sets.  Update the structure of type Library_Graph_Attributes
+	to remove the set of recorded cycles.
+	(Destroy_Library_Graph_Vertex): Move to the library level.
+	* bindo-writers.adb (Write_Component_Vertices): Output
+	information about the number of vertices.
+	* debug.adb: Document the use of binder switch -d_t.  Update the
+	use of binder switch -d_T.
+
 2019-07-10  Yannick Moy  <moy@adacore.com>
 
 	* sem_spark.adb (Get_Root_Object): Replace precondition by error

gcc/ada/bindo-graphs.ads

@@ -174,6 +174,11 @@ package Bindo.Graphs is
    First_Library_Graph_Vertex : constant Library_Graph_Vertex_Id :=
                                   No_Library_Graph_Vertex + 1;
 
+   procedure Destroy_Library_Graph_Vertex
+     (Vertex : in out Library_Graph_Vertex_Id);
+   pragma Inline (Destroy_Library_Graph_Vertex);
+   --  Destroy library graph vertex Vertex
+
    function Hash_Library_Graph_Vertex
      (Vertex : Library_Graph_Vertex_Id) return Bucket_Range_Type;
    pragma Inline (Hash_Library_Graph_Vertex);
@@ -183,6 +188,11 @@ package Bindo.Graphs is
    pragma Inline (Present);
    --  Determine whether library graph vertex Vertex exists
 
+   package LGV_Lists is new Doubly_Linked_Lists
+     (Element_Type    => Library_Graph_Vertex_Id,
+      "="             => "=",
+      Destroy_Element => Destroy_Library_Graph_Vertex);
+
    package LGV_Sets is new Membership_Sets
      (Element_Type => Library_Graph_Vertex_Id,
       "="          => "=",
@@ -1406,11 +1416,6 @@ package Bindo.Graphs is
       -- Vertices --
       --------------
 
-      procedure Destroy_Library_Graph_Vertex
-        (Vertex : in out Library_Graph_Vertex_Id);
-      pragma Inline (Destroy_Library_Graph_Vertex);
-      --  Destroy library graph vertex Vertex
-
       --  The following type represents the attributes of a library graph
       --  vertex.
 
@@ -1593,15 +1598,6 @@ package Bindo.Graphs is
          Destroy_Value         => Destroy_Library_Graph_Cycle_Attributes,
          Hash                  => Hash_Library_Graph_Cycle);
 
-      ---------------------
-      -- Recorded cycles --
-      ---------------------
-
-      package RC_Sets is new Membership_Sets
-        (Element_Type => Library_Graph_Cycle_Attributes,
-         "="          => Same_Library_Graph_Cycle_Attributes,
-         Hash         => Hash_Library_Graph_Cycle_Attributes);
-
       --------------------
       -- Recorded edges --
       --------------------
@@ -1693,10 +1689,6 @@ package Bindo.Graphs is
          --  The underlying graph describing the relations between edges and
          --  vertices.
 
-         Recorded_Cycles : RC_Sets.Membership_Set := RC_Sets.Nil;
-         --  The set of recorded cycles, used to prevent duplicate cycles in
-         --  the graph.
-
          Recorded_Edges : RE_Sets.Membership_Set := RE_Sets.Nil;
          --  The set of recorded edges, used to prevent duplicate edges in the
          --  graph.

gcc/ada/bindo-writers.adb

@@ -1102,6 +1102,8 @@ package body Bindo.Writers is
          Write_Eol;
 
          Write_Component_Vertices (G, Comp);
+
+         Write_Eol;
       end Write_Component;
 
       ------------------------------
@@ -1112,25 +1114,34 @@ package body Bindo.Writers is
         (G    : Library_Graph;
          Comp : Component_Id)
       is
+         pragma Assert (Present (G));
+         pragma Assert (Present (Comp));
+
+         Num_Of_Vertices : constant Natural :=
+                             Number_Of_Component_Vertices (G, Comp);
+
          Iter   : Component_Vertex_Iterator;
          Vertex : Library_Graph_Vertex_Id;
 
       begin
-         pragma Assert (Present (G));
-         pragma Assert (Present (Comp));
+         Write_Str ("  Vertices: ");
+         Write_Int (Int (Num_Of_Vertices));
+         Write_Eol;
 
-         Iter := Iterate_Component_Vertices (G, Comp);
-         while Has_Next (Iter) loop
-            Next (Iter, Vertex);
+         if Num_Of_Vertices > 0 then
+            Iter := Iterate_Component_Vertices (G, Comp);
+            while Has_Next (Iter) loop
+               Next (Iter, Vertex);
 
-            Write_Str  ("    library graph vertex (LGV_Id_");
-            Write_Int  (Int (Vertex));
-            Write_Str  (") name = ");
-            Write_Name (Name (G, Vertex));
+               Write_Str  ("    library graph vertex (LGV_Id_");
+               Write_Int  (Int (Vertex));
+               Write_Str  (") name = ");
+               Write_Name (Name (G, Vertex));
+               Write_Eol;
+            end loop;
+         else
             Write_Eol;
-         end loop;
-
-         Write_Eol;
+         end if;
       end Write_Component_Vertices;
 
       ----------------------

gcc/ada/bindo.adb

@@ -322,6 +322,11 @@ package body Bindo is
    --        In addition, GNATbind does not create an edge to the body of the
    --        pragma argument.
    --
+   --  -d_t  Output cycle detection trace information
+   --
+   --        GNATbind outputs trace information on cycle detection activities
+   --        to standard output.
+   --
    --  -d_A  Output ALI invocation tables
    --
    --        GNATbind outputs the contents of ALI table Invocation_Constructs
@@ -352,8 +357,8 @@ package body Bindo is
    --
    --  -d_T  Output elaboration-order trace information
    --
-   --        GNATbind outputs trace information on elaboration-order and cycle-
-   --        detection activities to standard output.
+   --        GNATbind outputs trace information on elaboration-order detection
+   --        activities to standard output.
    --
    --  -d_V  Validate bindo cycles, graphs, and order
    --
@@ -395,7 +400,7 @@ package body Bindo is
    --  number of files in the bind, Bindo may emit anywhere between several MBs
    --  to several hundred MBs of data to standard output. The switches are:
    --
-   --    -d_A -d_C -d_I -d_L -d_P -d_T -d_V
+   --    -d_A -d_C -d_I -d_L -d_P -d_t -d_T -d_V
    --
    --  Bindo offers several debugging routines that can be invoked from gdb.
    --  Those are defined in the body of Bindo.Writers, in sections denoted by

gcc/ada/debug.adb

@@ -368,7 +368,7 @@ package body Debug is
    --  d_q
    --  d_r
    --  d_s
-   --  d_t
+   --  d_t  Output cycle detection trace information
    --  d_u
    --  d_v
    --  d_w
@@ -380,6 +380,7 @@ package body Debug is
    --  d_B
    --  d_C  Diagnose all cycles
    --  d_D
+   --  d_E
    --  d_F
    --  d_G
    --  d_H
@@ -394,7 +395,7 @@ package body Debug is
    --  d_Q
    --  d_R
    --  d_S
-   --  d_T  Output elaboration order and cycle detection trace information
+   --  d_T  Output elaboration order trace information
    --  d_U
    --  d_V  Validate bindo cycles, graphs, and order
    --  d_W
@@ -1149,6 +1150,9 @@ package body Debug is
    --       elaboration order and no longer creates an implicit dependency on
    --       the body of the argument.
 
+   --  d_t  GNATBIND output trace information of cycle detection activities to
+   --       standard output.
+
    --  d_A  GNATBIND output the contents of all ALI invocation-related tables
    --       in textual format to standard output.
 
@@ -1163,8 +1167,8 @@ package body Debug is
 
    --  d_P  GNATBIND outputs the cycle paths to standard output
 
-   --  d_T  GNATBIND outputs trace information of elaboration order and cycle
-   --       detection activities to standard output.
+   --  d_T  GNATBIND outputs trace information of elaboration order detection
+   --       activities to standard output.
 
    --  d_V  GNATBIND validates the invocation graph, library graph along with
    --       its cycles, and the elaboration order.