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atree.ads, atree.adb (Traverse_Func): Walk Field2 last, and eliminate the resulting tail recursion by hand. 

2007-12-19  Bob Duff  <duff@adacore.com>

	* atree.ads, atree.adb (Traverse_Func): Walk Field2 last, and eliminate
	the resulting tail recursion by hand. This prevents running out of
	memory on deeply nested concatenations, since Field2 is where the left
	operand of concatenations is stored.
	Fix bug (was returning OK_Orig in some cases). Fix return subtype to
	clarify that it can only return OK or Abandon.

	* sem_res.adb (Resolve_Op_Concat): Replace the recursion on the left
	operand by iteration, in order to avoid running out of memory on
	deeply-nested concatenations. Use the Parent pointer to get back up the
	tree.
	(Resolve_Op_Concat_Arg, Resolve_Op_Concat_First,
	 Resolve_Op_Concat_Rest): New procedures split out of
	Resolve_Op_Concat, so the iterative algorithm in Resolve_Op_Concat is
	clearer.

	* checks.adb (Remove_Checks): Use Traverse_Proc instead of
	Traverse_Func, because the former already takes care of discarding the
	result.

	* errout.adb (First_Node): Use Traverse_Proc instead of Traverse_Func,
	because the former already takes care of discarding the result.
	(Remove_Warning_Messages): Use appropriate subtype for Status and
	Discard

From-SVN: r131070
This commit is contained in:
Bob Duff 2007-12-19 17:22:40 +01:00 committed by Arnaud Charlet
parent 160df97907
commit 10303118b3
5 changed files with 247 additions and 187 deletions
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81
gcc/ada/atree.adb
View File

@ -2624,12 +2624,12 @@ package body Atree is
-- Traverse_Func --
-------------------
function Traverse_Func (Node : Node_Id) return Traverse_Result is
function Traverse_Func (Node : Node_Id) return Traverse_Final_Result is
function Traverse_Field
(Nod : Node_Id;
Fld : Union_Id;
FN : Field_Num) return Traverse_Result;
FN : Field_Num) return Traverse_Final_Result;
-- Fld is one of the fields of Nod. If the field points to syntactic
-- node or list, then this node or list is traversed, and the result is
-- the result of this traversal. Otherwise a value of True is returned
@ -2642,7 +2642,7 @@ package body Atree is
function Traverse_Field
(Nod : Node_Id;
Fld : Union_Id;
FN : Field_Num) return Traverse_Result
FN : Field_Num) return Traverse_Final_Result
is
begin
if Fld = Union_Id (Empty) then
@ -2697,10 +2697,21 @@ package body Atree is
end if;
end Traverse_Field;
Cur_Node : Node_Id := Node;
-- Start of processing for Traverse_Func
begin
case Process (Node) is
-- We walk Field2 last, and if it is a node, we eliminate the tail
-- recursion by jumping back to this label. This is because Field2 is
-- where the Left_Opnd field of N_Op_Concat is stored, and in practice
-- concatenations are sometimes deeply nested, as in X1&X2&...&XN. This
-- trick prevents us from running out of memory in that case. We don't
-- bother eliminating the tail recursion if Field2 is a list.
<<Tail_Recurse>>
case Process (Cur_Node) is
when Abandon =>
return Abandon;
@ -2708,41 +2719,37 @@ package body Atree is
return OK;
when OK =>
if Traverse_Field (Node, Union_Id (Field1 (Node)), 1) = Abandon
or else
Traverse_Field (Node, Union_Id (Field2 (Node)), 2) = Abandon
or else
Traverse_Field (Node, Union_Id (Field3 (Node)), 3) = Abandon
or else
Traverse_Field (Node, Union_Id (Field4 (Node)), 4) = Abandon
or else
Traverse_Field (Node, Union_Id (Field5 (Node)), 5) = Abandon
then
return Abandon;
else
return OK;
end if;
null;
when OK_Orig =>
declare
Onod : constant Node_Id := Original_Node (Node);
begin
if Traverse_Field (Onod, Union_Id (Field1 (Onod)), 1) = Abandon
or else
Traverse_Field (Onod, Union_Id (Field2 (Onod)), 2) = Abandon
or else
Traverse_Field (Onod, Union_Id (Field3 (Onod)), 3) = Abandon
or else
Traverse_Field (Onod, Union_Id (Field4 (Onod)), 4) = Abandon
or else
Traverse_Field (Onod, Union_Id (Field5 (Onod)), 5) = Abandon
then
return Abandon;
else
return OK_Orig;
end if;
end;
Cur_Node := Original_Node (Cur_Node);
end case;
if Traverse_Field (Cur_Node, Field1 (Cur_Node), 1) = Abandon
or else -- skip Field2 here
Traverse_Field (Cur_Node, Field3 (Cur_Node), 3) = Abandon
or else
Traverse_Field (Cur_Node, Field4 (Cur_Node), 4) = Abandon
or else
Traverse_Field (Cur_Node, Field5 (Cur_Node), 5) = Abandon
then
return Abandon;
end if;
if Field2 (Cur_Node) not in Node_Range then
return Traverse_Field (Cur_Node, Field2 (Cur_Node), 2);
elsif Is_Syntactic_Field (Nkind (Cur_Node), 2) and then
Field2 (Cur_Node) /= Empty_List_Or_Node
then
-- Here is the tail recursion step, we reset Cur_Node and jump
-- back to the start of the procedure, which has the same
-- semantic effect as a call.
Cur_Node := Node_Id (Field2 (Cur_Node));
goto Tail_Recurse;
end if;
return OK;
end Traverse_Func;
-------------------
@ -2751,7 +2758,7 @@ package body Atree is
procedure Traverse_Proc (Node : Node_Id) is
function Traverse is new Traverse_Func (Process);
Discard : Traverse_Result;
Discard : Traverse_Final_Result;
pragma Warnings (Off, Discard);
begin
Discard := Traverse (Node);

18
gcc/ada/atree.ads
View File

@ -503,18 +503,22 @@ package Atree is
-- function is used only by Sinfo.CN to change nodes into their
-- corresponding entities.
type Traverse_Result is (OK, OK_Orig, Skip, Abandon);
type Traverse_Result is (Abandon, OK, OK_Orig, Skip);
-- This is the type of the result returned by the Process function passed
-- to Traverse_Func and Traverse_Proc and also the type of the result of
-- Traverse_Func itself. See descriptions below for details.
-- to Traverse_Func and Traverse_Proc. See below for details.
subtype Traverse_Final_Result is Traverse_Result range Abandon .. OK;
-- This is the type of the final result returned Traverse_Func, based on
-- the results of Process calls. See below for details.
generic
with function Process (N : Node_Id) return Traverse_Result is <>;
function Traverse_Func (Node : Node_Id) return Traverse_Result;
function Traverse_Func (Node : Node_Id) return Traverse_Final_Result;
-- This is a generic function that, given the parent node for a subtree,
-- traverses all syntactic nodes of this tree, calling the given function
-- Process on each one. The traversal is controlled as follows by the
-- result returned by Process:
-- Process on each one, in pre order (i.e. top-down). The order of
-- traversing subtrees is arbitrary. The traversal is controlled as follows
-- by the result returned by Process:
-- OK The traversal continues normally with the syntactic
-- children of the node just processed.
@ -537,7 +541,7 @@ package Atree is
with function Process (N : Node_Id) return Traverse_Result is <>;
procedure Traverse_Proc (Node : Node_Id);
pragma Inline (Traverse_Proc);
-- This is similar to Traverse_Func except that no result is returned,
-- This is the same as Traverse_Func except that no result is returned,
-- i.e. Traverse_Func is called and the result is simply discarded.
---------------------------

14
gcc/ada/checks.adb
View File

@ -2360,7 +2360,6 @@ package body Checks is
Analyze_And_Resolve (N, Typ);
return;
end if;
end Apply_Universal_Integer_Attribute_Checks;
-------------------------------
@ -5366,14 +5365,11 @@ package body Checks is
-------------------
procedure Remove_Checks (Expr : Node_Id) is
Discard : Traverse_Result;
pragma Warnings (Off, Discard);
function Process (N : Node_Id) return Traverse_Result;
-- Process a single node during the traversal
function Traverse is new Traverse_Func (Process);
-- The traversal function itself
procedure Traverse is new Traverse_Proc (Process);
-- The traversal procedure itself
-------------
-- Process --
@ -5389,7 +5385,7 @@ package body Checks is
case Nkind (N) is
when N_And_Then =>
Discard := Traverse (Left_Opnd (N));
Traverse (Left_Opnd (N));
return Skip;
when N_Attribute_Reference =>
@ -5425,7 +5421,7 @@ package body Checks is
end case;
when N_Or_Else =>
Discard := Traverse (Left_Opnd (N));
Traverse (Left_Opnd (N));
return Skip;
when N_Selected_Component =>
@ -5446,7 +5442,7 @@ package body Checks is
-- Start of processing for Remove_Checks
begin
Discard := Traverse (Expr);
Traverse (Expr);
end Remove_Checks;
----------------------------

13
gcc/ada/errout.adb
View File

@ -1235,15 +1235,12 @@ package body Errout is
Sfile : constant Source_File_Index := Get_Source_File_Index (L);
Earliest : Node_Id;
Eloc : Source_Ptr;
Discard : Traverse_Result;
pragma Warnings (Off, Discard);
function Test_Earlier (N : Node_Id) return Traverse_Result;
-- Function applied to every node in the construct
function Search_Tree_First is new Traverse_Func (Test_Earlier);
-- Create traversal function
procedure Search_Tree_First is new Traverse_Proc (Test_Earlier);
-- Create traversal procedure
------------------
-- Test_Earlier --
@ -1273,7 +1270,7 @@ package body Errout is
begin
Earliest := Original_Node (C);
Eloc := Sloc (Earliest);
Discard := Search_Tree_First (Original_Node (C));
Search_Tree_First (Original_Node (C));
return Earliest;
end First_Node;
@ -1982,7 +1979,7 @@ package body Errout is
-- to the tree is harmless.
declare
Status : Traverse_Result;
Status : Traverse_Final_Result;
begin
if Is_List_Member (N) then
@ -2006,7 +2003,7 @@ package body Errout is
begin
if Warnings_Detected /= 0 then
declare
Discard : Traverse_Result;
Discard : Traverse_Final_Result;
pragma Warnings (Off, Discard);
begin

308
gcc/ada/sem_res.adb
View File

@ -131,6 +131,23 @@ package body Sem_Res is
-- of the task, it must be replaced with a reference to the discriminant
-- of the task being called.
procedure Resolve_Op_Concat_Arg
(N : Node_Id;
Arg : Node_Id;
Typ : Entity_Id;
Is_Comp : Boolean);
-- Internal procedure for Resolve_Op_Concat to resolve one operand of
-- concatenation operator. The operand is either of the array type or of
-- the component type. If the operand is an aggregate, and the component
-- type is composite, this is ambiguous if component type has aggregates.
procedure Resolve_Op_Concat_First (N : Node_Id; Typ : Entity_Id);
-- Does the first part of the work of Resolve_Op_Concat
procedure Resolve_Op_Concat_Rest (N : Node_Id; Typ : Entity_Id);
-- Does the "rest" of the work of Resolve_Op_Concat, after the left operand
-- has been resolved. See Resolve_Op_Concat for details.
procedure Resolve_Allocator (N : Node_Id; Typ : Entity_Id);
procedure Resolve_Arithmetic_Op (N : Node_Id; Typ : Entity_Id);
procedure Resolve_Call (N : Node_Id; Typ : Entity_Id);
@ -6354,116 +6371,167 @@ package body Sem_Res is
-----------------------
procedure Resolve_Op_Concat (N : Node_Id; Typ : Entity_Id) is
-- We wish to avoid deep recursion, because concatenations are often
-- deeply nested, as in A&B&...&Z. Therefore, we walk down the left
-- operands nonrecursively until we find something that is not a simple
-- concatenation (A in this case). We resolve that, and then walk back
-- up the tree following Parent pointers, calling Resolve_Op_Concat_Rest
-- to do the rest of the work at each level. The Parent pointers allow
-- us to avoid recursion, and thus avoid running out of memory. See also
-- Sem_Ch4.Analyze_Concatenation, where a similar hack is used.
NN : Node_Id := N;
Op1 : Node_Id;
begin
-- The following code is equivalent to:
-- Resolve_Op_Concat_First (NN, Typ);
-- Resolve_Op_Concat_Arg (N, ...);
-- Resolve_Op_Concat_Rest (N, Typ);
-- where the Resolve_Op_Concat_Arg call recurses back here if the left
-- operand is a concatenation.
-- Walk down left operands
loop
Resolve_Op_Concat_First (NN, Typ);
Op1 := Left_Opnd (NN);
exit when not (Nkind (Op1) = N_Op_Concat
and then not Is_Array_Type (Component_Type (Typ))
and then Entity (Op1) = Entity (NN));
NN := Op1;
end loop;
-- Now (given the above example) NN is A&B and Op1 is A
-- First resolve Op1 ...
Resolve_Op_Concat_Arg (NN, Op1, Typ, Is_Component_Left_Opnd (NN));
-- ... then walk NN back up until we reach N (where we started), calling
-- Resolve_Op_Concat_Rest along the way.
loop
Resolve_Op_Concat_Rest (NN, Typ);
exit when NN = N;
NN := Parent (NN);
end loop;
end Resolve_Op_Concat;
---------------------------
-- Resolve_Op_Concat_Arg --
---------------------------
procedure Resolve_Op_Concat_Arg
(N : Node_Id;
Arg : Node_Id;
Typ : Entity_Id;
Is_Comp : Boolean)
is
Btyp : constant Entity_Id := Base_Type (Typ);
Op1 : constant Node_Id := Left_Opnd (N);
Op2 : constant Node_Id := Right_Opnd (N);
procedure Resolve_Concatenation_Arg (Arg : Node_Id; Is_Comp : Boolean);
-- Internal procedure to resolve one operand of concatenation operator.
-- The operand is either of the array type or of the component type.
-- If the operand is an aggregate, and the component type is composite,
-- this is ambiguous if component type has aggregates.
-------------------------------
-- Resolve_Concatenation_Arg --
-------------------------------
procedure Resolve_Concatenation_Arg (Arg : Node_Id; Is_Comp : Boolean) is
begin
if In_Instance then
if Is_Comp
or else (not Is_Overloaded (Arg)
and then Etype (Arg) /= Any_Composite
and then Covers (Component_Type (Typ), Etype (Arg)))
then
Resolve (Arg, Component_Type (Typ));
else
Resolve (Arg, Btyp);
end if;
elsif Has_Compatible_Type (Arg, Component_Type (Typ)) then
if Nkind (Arg) = N_Aggregate
and then Is_Composite_Type (Component_Type (Typ))
then
if Is_Private_Type (Component_Type (Typ)) then
Resolve (Arg, Btyp);
else
Error_Msg_N ("ambiguous aggregate must be qualified", Arg);
Set_Etype (Arg, Any_Type);
end if;
else
if Is_Overloaded (Arg)
and then Has_Compatible_Type (Arg, Typ)
and then Etype (Arg) /= Any_Type
then
declare
I : Interp_Index;
It : Interp;
Func : Entity_Id;
begin
Get_First_Interp (Arg, I, It);
Func := It.Nam;
Get_Next_Interp (I, It);
-- Special-case the error message when the overloading
-- is caused by a function that yields and array and
-- can be called without parameters.
if It.Nam = Func then
Error_Msg_Sloc := Sloc (Func);
Error_Msg_N ("ambiguous call to function#", Arg);
Error_Msg_NE
("\\interpretation as call yields&", Arg, Typ);
Error_Msg_NE
("\\interpretation as indexing of call yields&",
Arg, Component_Type (Typ));
else
Error_Msg_N
("ambiguous operand for concatenation!", Arg);
Get_First_Interp (Arg, I, It);
while Present (It.Nam) loop
Error_Msg_Sloc := Sloc (It.Nam);
if Base_Type (It.Typ) = Base_Type (Typ)
or else Base_Type (It.Typ) =
Base_Type (Component_Type (Typ))
then
Error_Msg_N ("\\possible interpretation#", Arg);
end if;
Get_Next_Interp (I, It);
end loop;
end if;
end;
end if;
Resolve (Arg, Component_Type (Typ));
if Nkind (Arg) = N_String_Literal then
Set_Etype (Arg, Component_Type (Typ));
end if;
if Arg = Left_Opnd (N) then
Set_Is_Component_Left_Opnd (N);
else
Set_Is_Component_Right_Opnd (N);
end if;
end if;
begin
if In_Instance then
if Is_Comp
or else (not Is_Overloaded (Arg)
and then Etype (Arg) /= Any_Composite
and then Covers (Component_Type (Typ), Etype (Arg)))
then
Resolve (Arg, Component_Type (Typ));
else
Resolve (Arg, Btyp);
end if;
Check_Unset_Reference (Arg);
end Resolve_Concatenation_Arg;
elsif Has_Compatible_Type (Arg, Component_Type (Typ)) then
if Nkind (Arg) = N_Aggregate
and then Is_Composite_Type (Component_Type (Typ))
then
if Is_Private_Type (Component_Type (Typ)) then
Resolve (Arg, Btyp);
else
Error_Msg_N ("ambiguous aggregate must be qualified", Arg);
Set_Etype (Arg, Any_Type);
end if;
-- Start of processing for Resolve_Op_Concat
else
if Is_Overloaded (Arg)
and then Has_Compatible_Type (Arg, Typ)
and then Etype (Arg) /= Any_Type
then
declare
I : Interp_Index;
It : Interp;
Func : Entity_Id;
begin
Get_First_Interp (Arg, I, It);
Func := It.Nam;
Get_Next_Interp (I, It);
-- Special-case the error message when the overloading is
-- caused by a function that yields an array and can be
-- called without parameters.
if It.Nam = Func then
Error_Msg_Sloc := Sloc (Func);
Error_Msg_N ("ambiguous call to function#", Arg);
Error_Msg_NE
("\\interpretation as call yields&", Arg, Typ);
Error_Msg_NE
("\\interpretation as indexing of call yields&",
Arg, Component_Type (Typ));
else
Error_Msg_N
("ambiguous operand for concatenation!", Arg);
Get_First_Interp (Arg, I, It);
while Present (It.Nam) loop
Error_Msg_Sloc := Sloc (It.Nam);
if Base_Type (It.Typ) = Base_Type (Typ)
or else Base_Type (It.Typ) =
Base_Type (Component_Type (Typ))
then
Error_Msg_N ("\\possible interpretation#", Arg);
end if;
Get_Next_Interp (I, It);
end loop;
end if;
end;
end if;
Resolve (Arg, Component_Type (Typ));
if Nkind (Arg) = N_String_Literal then
Set_Etype (Arg, Component_Type (Typ));
end if;
if Arg = Left_Opnd (N) then
Set_Is_Component_Left_Opnd (N);
else
Set_Is_Component_Right_Opnd (N);
end if;
end if;
else
Resolve (Arg, Btyp);
end if;
Check_Unset_Reference (Arg);
end Resolve_Op_Concat_Arg;
-----------------------------
-- Resolve_Op_Concat_First --
-----------------------------
procedure Resolve_Op_Concat_First (N : Node_Id; Typ : Entity_Id) is
Btyp : constant Entity_Id := Base_Type (Typ);
Op1 : constant Node_Id := Left_Opnd (N);
Op2 : constant Node_Id := Right_Opnd (N);
begin
-- The parser folds an enormous sequence of concatenations of string
@ -6488,30 +6556,18 @@ package body Sem_Res is
Error_Msg_N ("concatenation not available for limited array", N);
Explain_Limited_Type (Btyp, N);
end if;
end Resolve_Op_Concat_First;
-- If the operands are themselves concatenations, resolve them as such
-- directly. This removes several layers of recursion and allows GNAT to
-- handle larger multiple concatenations.
----------------------------
-- Resolve_Op_Concat_Rest --
----------------------------
if Nkind (Op1) = N_Op_Concat
and then not Is_Array_Type (Component_Type (Typ))
and then Entity (Op1) = Entity (N)
then
Resolve_Op_Concat (Op1, Typ);
else
Resolve_Concatenation_Arg
(Op1, Is_Component_Left_Opnd (N));
end if;
procedure Resolve_Op_Concat_Rest (N : Node_Id; Typ : Entity_Id) is
Op1 : constant Node_Id := Left_Opnd (N);
Op2 : constant Node_Id := Right_Opnd (N);
if Nkind (Op2) = N_Op_Concat
and then not Is_Array_Type (Component_Type (Typ))
and then Entity (Op2) = Entity (N)
then
Resolve_Op_Concat (Op2, Typ);
else
Resolve_Concatenation_Arg
(Op2, Is_Component_Right_Opnd (N));
end if;
begin
Resolve_Op_Concat_Arg (N, Op2, Typ, Is_Component_Right_Opnd (N));
Generate_Operator_Reference (N, Typ);
@ -6520,7 +6576,7 @@ package body Sem_Res is
end if;
-- If this is not a static concatenation, but the result is a
-- string type (and not an array of strings) insure that static
-- string type (and not an array of strings) ensure that static
-- string operands have their subtypes properly constructed.
if Nkind (N) /= N_String_Literal
@ -6529,7 +6585,7 @@ package body Sem_Res is
Set_String_Literal_Subtype (Op1, Typ);
Set_String_Literal_Subtype (Op2, Typ);
end if;
end Resolve_Op_Concat;
end Resolve_Op_Concat_Rest;
----------------------
-- Resolve_Op_Expon --