-- --
-- B o d y --
-- --
--- $Revision: 1.18 $ --
--- --
--- Copyright (C) 1992-1998, Free Software Foundation, Inc. --
+-- Copyright (C) 1992-2006, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
--- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
--- MA 02111-1307, USA. --
+-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
+-- Boston, MA 02110-1301, USA. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
--- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
+-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- Next label node to process
function Find_Enclosing_Body_Or_Block (N : Node_Id) return Node_Id;
- -- Find the innermost body or block that encloses N.
+ -- Find the innermost body or block that encloses N
function Find_Enclosing_Body (N : Node_Id) return Node_Id;
- -- Find the innermost body that encloses N.
+ -- Find the innermost body that encloses N
procedure Check_Distinct_Labels;
-- Checks the rule in RM-5.1(11), which requires distinct identifiers
-- for all the labels in a given body.
+ procedure Find_Natural_Loops;
+ -- Recognizes loops created by backward gotos, and rewrites the
+ -- corresponding statements into a proper loop, for optimization
+ -- purposes (for example, to control reclaiming local storage).
+
---------------------------
-- Check_Distinct_Labels --
---------------------------
Result : Node_Id := Parent (N);
begin
- -- Climb up the parent chain until we find a body or block.
+ -- Climb up the parent chain until we find a body or block
while Present (Result)
and then Nkind (Result) /= N_Accept_Statement
return Result;
end Find_Enclosing_Body_Or_Block;
+ ------------------------
+ -- Find_Natural_Loops --
+ ------------------------
+
+ procedure Find_Natural_Loops is
+ Node_List : constant Elist_Id := New_Elmt_List;
+ N : Elmt_Id;
+ Succ : Elmt_Id;
+
+ function Goto_Id (Goto_Node : Node_Id) return Name_Id;
+ -- Find Name_Id of goto statement, which may be an expanded name
+
+ function Matches
+ (Label_Node : Node_Id;
+ Goto_Node : Node_Id) return Boolean;
+ -- A label and a goto are candidates for a loop if the names match,
+ -- and both nodes appear in the same body. In addition, both must
+ -- appear in the same statement list. If they are not in the same
+ -- statement list, the goto is from within an nested structure, and
+ -- the label is not a header. We ignore the case where the goto is
+ -- within a conditional structure, and capture only infinite loops.
+
+ procedure Merge;
+ -- Merge labels and goto statements in order of increasing sloc value.
+ -- Discard labels of loop and block statements.
+
+ procedure No_Header (N : Elmt_Id);
+ -- The label N is known not to be a loop header. Scan forward and
+ -- remove all subsequent goto's that may have this node as a target.
+
+ procedure Process_Goto (N : Elmt_Id);
+ -- N is a forward jump. Scan forward and remove all subsequent goto's
+ -- that may have the same target, to preclude spurious loops.
+
+ procedure Rewrite_As_Loop
+ (Loop_Header : Node_Id;
+ Loop_End : Node_Id);
+ -- Given a label and a backwards goto, rewrite intervening statements
+ -- as a loop. Remove the label from the node list, and rewrite the
+ -- goto with the body of the new loop.
+
+ procedure Try_Loop (N : Elmt_Id);
+ -- N is a label that may be a loop header. Scan forward to find some
+ -- backwards goto with which to make a loop. Do nothing if there is
+ -- an intervening label that is not part of a loop, or more than one
+ -- goto with this target.
+
+ -------------
+ -- Goto_Id --
+ -------------
+
+ function Goto_Id (Goto_Node : Node_Id) return Name_Id is
+ begin
+ if Nkind (Name (Goto_Node)) = N_Identifier then
+ return Chars (Name (Goto_Node));
+
+ elsif Nkind (Name (Goto_Node)) = N_Selected_Component then
+ return Chars (Selector_Name (Name (Goto_Node)));
+ else
+
+ -- In case of error, return Id that can't match anything
+
+ return Name_Null;
+ end if;
+ end Goto_Id;
+
+ -------------
+ -- Matches --
+ -------------
+
+ function Matches
+ (Label_Node : Node_Id;
+ Goto_Node : Node_Id) return Boolean
+ is
+ begin
+ return Chars (Identifier (Label_Node)) = Goto_Id (Goto_Node)
+ and then Find_Enclosing_Body (Label_Node) =
+ Find_Enclosing_Body (Goto_Node);
+ end Matches;
+
+ -----------
+ -- Merge --
+ -----------
+
+ procedure Merge is
+ L1 : Elmt_Id;
+ G1 : Elmt_Id;
+
+ begin
+ L1 := First_Elmt (Label_List);
+ G1 := First_Elmt (Goto_List);
+
+ while Present (L1)
+ and then Present (G1)
+ loop
+ if Sloc (Node (L1)) < Sloc (Node (G1)) then
+
+ -- Optimization: remove labels of loops and blocks, which
+ -- play no role in what follows.
+
+ if Nkind (Node (L1)) /= N_Loop_Statement
+ and then Nkind (Node (L1)) /= N_Block_Statement
+ then
+ Append_Elmt (Node (L1), Node_List);
+ end if;
+
+ Next_Elmt (L1);
+
+ else
+ Append_Elmt (Node (G1), Node_List);
+ Next_Elmt (G1);
+ end if;
+ end loop;
+
+ while Present (L1) loop
+ Append_Elmt (Node (L1), Node_List);
+ Next_Elmt (L1);
+ end loop;
+
+ while Present (G1) loop
+ Append_Elmt (Node (G1), Node_List);
+ Next_Elmt (G1);
+ end loop;
+ end Merge;
+
+ ---------------
+ -- No_Header --
+ ---------------
+
+ procedure No_Header (N : Elmt_Id) is
+ S1, S2 : Elmt_Id;
+
+ begin
+ S1 := Next_Elmt (N);
+ while Present (S1) loop
+ S2 := Next_Elmt (S1);
+ if Nkind (Node (S1)) = N_Goto_Statement
+ and then Matches (Node (N), Node (S1))
+ then
+ Remove_Elmt (Node_List, S1);
+ end if;
+
+ S1 := S2;
+ end loop;
+ end No_Header;
+
+ ------------------
+ -- Process_Goto --
+ ------------------
+
+ procedure Process_Goto (N : Elmt_Id) is
+ Goto1 : constant Node_Id := Node (N);
+ Goto2 : Node_Id;
+ S, S1 : Elmt_Id;
+
+ begin
+ S := Next_Elmt (N);
+
+ while Present (S) loop
+ S1 := Next_Elmt (S);
+ Goto2 := Node (S);
+
+ if Nkind (Goto2) = N_Goto_Statement
+ and then Goto_Id (Goto1) = Goto_Id (Goto2)
+ and then Find_Enclosing_Body (Goto1) =
+ Find_Enclosing_Body (Goto2)
+ then
+
+ -- Goto2 may have the same target, remove it from
+ -- consideration.
+
+ Remove_Elmt (Node_List, S);
+ end if;
+
+ S := S1;
+ end loop;
+ end Process_Goto;
+
+ ---------------------
+ -- Rewrite_As_Loop --
+ ---------------------
+
+ procedure Rewrite_As_Loop
+ (Loop_Header : Node_Id;
+ Loop_End : Node_Id)
+ is
+ Loop_Body : constant List_Id := New_List;
+ Loop_Stmt : constant Node_Id :=
+ New_Node (N_Loop_Statement, Sloc (Loop_Header));
+ Stat : Node_Id;
+ Next_Stat : Node_Id;
+ begin
+ Stat := Next (Loop_Header);
+ while Stat /= Loop_End loop
+ Next_Stat := Next (Stat);
+ Remove (Stat);
+ Append (Stat, Loop_Body);
+ Stat := Next_Stat;
+ end loop;
+
+ Set_Statements (Loop_Stmt, Loop_Body);
+ Set_Identifier (Loop_Stmt, Identifier (Loop_Header));
+
+ Remove (Loop_Header);
+ Rewrite (Loop_End, Loop_Stmt);
+ Error_Msg_N
+ ("code between label and backwards goto rewritten as loop?",
+ Loop_End);
+ end Rewrite_As_Loop;
+
+ --------------
+ -- Try_Loop --
+ --------------
+
+ procedure Try_Loop (N : Elmt_Id) is
+ Source : Elmt_Id;
+ Found : Boolean := False;
+ S1 : Elmt_Id;
+
+ begin
+ S1 := Next_Elmt (N);
+ while Present (S1) loop
+ if Nkind (Node (S1)) = N_Goto_Statement
+ and then Matches (Node (N), Node (S1))
+ then
+ if not Found then
+ if Parent (Node (N)) = Parent (Node (S1)) then
+ Source := S1;
+ Found := True;
+
+ else
+ -- The goto is within some nested structure
+
+ No_Header (N);
+ return;
+ end if;
+
+ else
+ -- More than one goto with the same target
+
+ No_Header (N);
+ return;
+ end if;
+
+ elsif Nkind (Node (S1)) = N_Label
+ and then not Found
+ then
+ -- Intervening label before possible end of loop. Current
+ -- label is not a candidate. This is conservative, because
+ -- the label might not be the target of any jumps, but not
+ -- worth dealing with useless labels!
+
+ No_Header (N);
+ return;
+
+ else
+ -- If the node is a loop_statement, it corresponds to a
+ -- label-goto pair rewritten as a loop. Continue forward scan.
+
+ null;
+ end if;
+
+ Next_Elmt (S1);
+ end loop;
+
+ if Found then
+ Rewrite_As_Loop (Node (N), Node (Source));
+ Remove_Elmt (Node_List, N);
+ Remove_Elmt (Node_List, Source);
+ end if;
+ end Try_Loop;
+
+ begin
+ -- Start of processing for Find_Natural_Loops
+
+ Merge;
+
+ N := First_Elmt (Node_List);
+ while Present (N) loop
+ Succ := Next_Elmt (N);
+
+ if Nkind (Node (N)) = N_Label then
+ if No (Succ) then
+ exit;
+
+ elsif Nkind (Node (Succ)) = N_Label then
+ Try_Loop (Succ);
+
+ -- If a loop was found, the label has been removed, and
+ -- the following goto rewritten as the loop body.
+
+ Succ := Next_Elmt (N);
+
+ if Nkind (Node (Succ)) = N_Label then
+
+ -- Following label was not removed, so current label
+ -- is not a candidate header.
+
+ No_Header (N);
+
+ else
+
+ -- Following label was part of inner loop. Current
+ -- label is still a candidate.
+
+ Try_Loop (N);
+ Succ := Next_Elmt (N);
+ end if;
+
+ elsif Nkind (Node (Succ)) = N_Goto_Statement then
+ Try_Loop (N);
+ Succ := Next_Elmt (N);
+ end if;
+
+ elsif Nkind (Node (N)) = N_Goto_Statement then
+ Process_Goto (N);
+ Succ := Next_Elmt (N);
+ end if;
+
+ N := Succ;
+ end loop;
+ end Find_Natural_Loops;
+
-- Start of processing for Par.Labl
begin
Next_Label_Elmt := First_Elmt (Label_List);
-
while Present (Next_Label_Elmt) loop
Label_Node := Node (Next_Label_Elmt);
Set_Defining_Identifier (Label_Decl_Node, Defining_Ident_Node);
Set_Label_Construct (Label_Decl_Node, Label_Node);
+ -- The following makes sure that Comes_From_Source is appropriately
+ -- set for the entity, depending on whether the label appeared in
+ -- the source explicitly or not.
+
+ Set_Comes_From_Source
+ (Defining_Ident_Node, Comes_From_Source (Identifier (Label_Node)));
+
-- Now attach the implicit label declaration to the appropriate
-- declarative region, creating a declaration list if none exists
- if not Present (Declarations (Enclosing_Body_Or_Block)) then
+ if No (Declarations (Enclosing_Body_Or_Block)) then
Set_Declarations (Enclosing_Body_Or_Block, New_List);
end if;
Next_Elmt (Next_Label_Elmt);
end loop;
+ Find_Natural_Loops;
+
end Labl;
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