[Ada] Tech debt: Expansion of contracts

This patch modifies the expansion of contracts such that the statements
and declarations of a subprogram with post-execution checks get moved to
a local internally generated subprogram which the original subprogram
calls directly followed by the required post-execution checks.

This differs from the current implementation which requires delicate
machinary which coordinates with the finalization process to emulate the
desired behavior within the "at end" procedure.

gcc/ada/

	* contracts.adb, contracts.ads
	(Analyze_Pragmas_In_Declarations): Added to aid in the new
	expansion model so that pragmas relating to contracts can get
	processed early before the rest of the subprogram containing them.
	(Build_Subprogram_Contract_Wrapper): Created to do the majority of
	expansion for postconditions. It builds a local wrapper with the
	statements and declarations within a given subprogram.
	(Is_Prologue_Renaming): Moved out from Process_Preconditions to be
	used generally within the contracts package.
	(Build_Entry_Contract_Wrapper): Moved from exp_ch7.
	(Expand_Subprogram_Contract): Add new local variable Decls to
	store expanded declarations needed for evaluation of contracts.
	Call new wrapper building procedure and modify comments to match
	new expansion model.
	(Get_Postcond_Enabled): Deleted.
	(Get_Result_Object_For_Postcond): Deleted.
	(Get_Return_Success_For_Postcond): Deleted.
	(Process_Contract_Cases): Add new parameter to store declarations.
	(Process_Postconditions): Add new parameter to store declarations.
	(Process_Preconditions): Add new parameter to store declarations.
	Add code to move entry-call prologue renamings
	* einfo.ads: Document new field Wrapped_Statements and modify
	comment for Postconditions_Proc.
	* exp_attr.adb
	(Analyze_Attribute): Modify expansion of the 'Old attribute to
	recognize new expansion model and use Wrapped_Statements instead
	of Postconditions_Proc.
	* exp_ch6.adb
	(Add_Return): Remove special expansion for postconditions.
	(Expand_Call): Modify condition checking for calls to access
	subprogram wrappers to handle new expansion models.
	(Expand_Call_Helper): Remove special expansion for postconditions.
	(Expand_Non_Function_Return): Remove special expansion for
	postconditions.
	(Expand_Simple_Function_Return): Remove special expansion for
	postconditions.
	* exp_ch7.adb
	(Build_Finalizer): Deleted, but replaced by code in
	Build_Finalizer_Helper
	(Build_Finalizer_Helper): Renamed to Build_Finalizer, and special
	handling of 'Old objects removed.
	* exp_ch9.adb
	(Build_Contract_Wrapper): Renamed and moved to contracts package.
	* exp_prag.adb
	(Expand_Pragma_Contract_Cases): Delay analysis of contracts since
	they now instead get analyzed as part of the wrapper generation
	instead of after analysis of their corresponding subprogram's
	body.
	(Expand_Pragma_Check): Label expanded if-statements which come
	from the expansion of assertion statements as
	Comes_From_Check_Or_Contract.
	* freeze.adb
	(Freeze_Entity): Add special case to avoid freezing when a freeze
	node gets generated as part of the expansion of a postcondition
	check.
	* gen_il-gen-gen_nodes.adb: Add new flag
	Comes_From_Check_Or_Contract.
	* gen_il-fields.ads: Add new field Wrapped_Statements. Add new
	flag Comes_From_Check_Or_Contract.
	* gen_il-gen-gen_entities.adb: Add new field Wrapped_Statements.
	* ghost.adb
	(Is_OK_Declaration): Replace Name_uPostconditions with
	Name_uWrapped_Statements.
	(Is_OK_Statement): Simplify condition due to the loss of
	Original_Node as a result of the new expansion model of contracts
	and use new flag Comes_From_Check_Or_Contract in its place.
	* inline.adb
	(Declare_Postconditions_Result): Replace Name_uPostconditions with
	Name_uWrapped_Statements.
	(Expand_Inlined_Call): Replace Name_uPostconditions with
	Name_uWrapped_Statements.
	* lib.adb, lib.ads
	(ipu): Created to aid in debugging.
	* lib-xref.adb
	(Generate_References): Remove special handling for postcondition
	procedures.
	* sem_attr.adb
	(Analyze_Attribute_Old_Result): Add new context in which 'Old can
	appear due to the changes in expansion. Replace
	Name_uPostconditions with Name_uWrapped_Statements.
	(Result): Replace Name_uPostconditions with
	Name_uWrapped_Statements.
	* sem_ch11.adb
	(Analyze_Handled_Statements): Remove check to exclude warnings on
	useless assignments within postcondition procedures since
	postconditions no longer get isolated into separate subprograms.
	* sem_ch6.adb
	(Analyze_Generic_Subprogram_Body): Modify expansion of generic
	subprogram bodies so that contracts (and their associated pragmas)
	get analyzed first.
	(Analyze_Subprogram_Body_Helper): Remove global HSS variable due
	to the HSS of the body potentially changing during the expansion
	of contracts. In cases where it was used instead directly call
	Handled_Statement_Sequence. Modify expansion of subprogram bodies
	so that contracts (and their associated pragmas) get analyzed
	first.
	(Check_Missing_Return): Create local HSS variable instead of using
	a global one.
	(Move_Pragmas): Use new pragma table instead of an explicit list.
	* sem_elab.adb
	(Is_Postconditions_Proc): Deleted since the new scheme of
	expansion no longer divides postcondition checks to a separate
	subprogram and so cannot be easily identified (similar to
	pre-condition checks).
	(Info_Call): Remove info printing for _Postconditions subprograms.
	(Is_Assertion_Pragma_Target): Remove check for postconditions
	procedure
	(Is_Bridge_Target): Remove check for postconditions procedure.
	(Get_Invocation_Attributes): Remove unneeded local variables and
	check for postconditions procedure.
	(Output_Call): Remove info printing for _Postconditions
	subprograms.
	* sem_prag.adb, sem_prag.ads: Add new Pragma table for pragmas
	significant to subprograms, along with tech-debt comment.
	(Check_Arg_Is_Local_Name): Modified to recognize the new
	_Wrapped_Statements internal subprogram and the new expansion
	model.
	(Relocate_Pragmas_To_Body): Replace Name_uPostconditions with
	Name_uWrapped_Statements.
	* sem_res.adb
	(Resolve_Entry_Call): Add conditional to detect both contract
	based wrappers of entries, but also wrappers generated as part of
	general contract expansion (e.g. local postconditions
	subprograms).
	* sem_util.adb
	(Accessibility_Level): Verify 'Access is not taken based on a
	component of a function result.
	(Has_Significant_Contracts): Replace Name_uPostconditions with
	Name_uWrapped_Statements.
	(Same_Or_Aliased_Subprogram): Add conditional to detect and obtain
	the original subprogram based on the new concept of
	"postcondition" wrappers.
	* sinfo.ads: Add documentation for new flag
	Comes_From_Check_Or_Contract.
	* snames.ads-tmpl: Remove Name_uPostconditions and add
	Name_uWrapped_Statements

1 files changed, 39 insertions, 46 deletions

diff --git a/gcc/ada/sem_ch6.adb b/gcc/ada/sem_ch6.adb
index 93eeecb..0459058 100644
--- a/gcc/ada/sem_ch6.adb
+++ b/gcc/ada/sem_ch6.adb
@@ -1911,15 +1911,19 @@ package body Sem_Ch6 is
             Analyze_Aspects_On_Subprogram_Body_Or_Stub (N);
          end if;
 
-         Analyze_Declarations (Declarations (N));
-         Check_Completion;
-
-         --  Process the contract of the subprogram body after all declarations
-         --  have been analyzed. This ensures that any contract-related pragmas
-         --  are available through the N_Contract node of the body.
+         --  Process the contract of the subprogram body after analyzing all
+         --  the contract-related pragmas within the declarations.
 
+         Analyze_Pragmas_In_Declarations (Body_Id);
          Analyze_Entry_Or_Subprogram_Body_Contract (Body_Id);
 
+         --  Continue on with analyzing the declarations and statements once
+         --  contract expansion is done and we are done expanding contract
+         --  related wrappers.
+
+         Analyze_Declarations (Declarations (N));
+         Check_Completion;
+
          Analyze (Handled_Statement_Sequence (N));
          Save_Global_References (Original_Node (N));
 
@@ -2895,7 +2899,6 @@ package body Sem_Ch6 is
       Conformant : Boolean;
       Desig_View : Entity_Id := Empty;
       Exch_Views : Elist_Id  := No_Elist;
-      HSS        : Node_Id;
       Mask_Types : Elist_Id  := No_Elist;
       Prot_Typ   : Entity_Id := Empty;
       Spec_Decl  : Node_Id   := Empty;
@@ -3530,6 +3533,8 @@ package body Sem_Ch6 is
       --------------------------
 
       procedure Check_Missing_Return is
+         HSS : constant Node_Id := Handled_Statement_Sequence (N);
+
          Id          : Entity_Id;
          Missing_Ret : Boolean;
 
@@ -3968,18 +3973,9 @@ package body Sem_Ch6 is
 
                --  Move relevant pragmas to the spec
 
-               elsif Pragma_Name_Unmapped (Decl) in Name_Depends
-                                                  | Name_Ghost
-                                                  | Name_Global
-                                                  | Name_Pre
-                                                  | Name_Precondition
-                                                  | Name_Post
-                                                  | Name_Refined_Depends
-                                                  | Name_Refined_Global
-                                                  | Name_Refined_Post
-                                                  | Name_Inline
-                                                  | Name_Pure_Function
-                                                  | Name_Volatile_Function
+               elsif
+                 Pragma_Significant_To_Subprograms
+                   (Get_Pragma_Id (Decl))
                then
                   Remove (Decl);
                   Insert_After (Insert_Nod, Decl);
@@ -4223,7 +4219,6 @@ package body Sem_Ch6 is
             Analyze_Generic_Subprogram_Body (N, Spec_Id);
 
             if Nkind (N) = N_Subprogram_Body then
-               HSS := Handled_Statement_Sequence (N);
                Check_Missing_Return;
             end if;
 
@@ -5157,9 +5152,27 @@ package body Sem_Ch6 is
          end;
       end if;
 
-      --  Now we can go on to analyze the body
+      --  Ada 2012 (AI05-0151): Incomplete types coming from a limited context
+      --  may now appear in parameter and result profiles. Since the analysis
+      --  of a subprogram body may use the parameter and result profile of the
+      --  spec, swap any limited views with their non-limited counterpart.
+
+      if Ada_Version >= Ada_2012 and then Present (Spec_Id) then
+         Exch_Views := Exchange_Limited_Views (Spec_Id);
+      end if;
+
+      --  Analyze any aspect specifications that appear on the subprogram body
+
+      if Has_Aspects (N) then
+         Analyze_Aspects_On_Subprogram_Body_Or_Stub (N);
+      end if;
+
+      --  Process the contract of the subprogram body after analyzing all the
+      --  contract-related pragmas within the declarations.
+
+      Analyze_Pragmas_In_Declarations (Body_Id);
+      Analyze_Entry_Or_Subprogram_Body_Contract (Body_Id);
 
-      HSS := Handled_Statement_Sequence (N);
       Set_Actual_Subtypes (N, Current_Scope);
 
       --  Add a declaration for the Protection object, renaming declarations
@@ -5180,15 +5193,6 @@ package body Sem_Ch6 is
            (Sloc (N), Spec_Id, Prot_Typ, N, Declarations (N));
       end if;
 
-      --  Ada 2012 (AI05-0151): Incomplete types coming from a limited context
-      --  may now appear in parameter and result profiles. Since the analysis
-      --  of a subprogram body may use the parameter and result profile of the
-      --  spec, swap any limited views with their non-limited counterpart.
-
-      if Ada_Version >= Ada_2012 and then Present (Spec_Id) then
-         Exch_Views := Exchange_Limited_Views (Spec_Id);
-      end if;
-
       --  If the return type is an anonymous access type whose designated type
       --  is the limited view of a class-wide type and the non-limited view is
       --  available, update the return type accordingly.
@@ -5225,12 +5229,6 @@ package body Sem_Ch6 is
          end;
       end if;
 
-      --  Analyze any aspect specifications that appear on the subprogram body
-
-      if Has_Aspects (N) then
-         Analyze_Aspects_On_Subprogram_Body_Or_Stub (N);
-      end if;
-
       Analyze_Declarations (Declarations (N));
 
       --  Verify that the SPARK_Mode of the body agrees with that of its spec
@@ -5269,17 +5267,11 @@ package body Sem_Ch6 is
          end if;
       end if;
 
-      --  A subprogram body freezes its own contract. Analyze the contract
-      --  after the declarations of the body have been processed as pragmas
-      --  are now chained on the contract of the subprogram body.
-
-      Analyze_Entry_Or_Subprogram_Body_Contract (Body_Id);
-
       --  Check completion, and analyze the statements
 
       Check_Completion;
       Inspect_Deferred_Constant_Completion (Declarations (N));
-      Analyze (HSS);
+      Analyze (Handled_Statement_Sequence (N));
 
       --  Add the generated minimum accessibility objects to the subprogram
       --  body's list of declarations after analysis of the statements and
@@ -5296,7 +5288,8 @@ package body Sem_Ch6 is
 
       --  Deal with end of scope processing for the body
 
-      Process_End_Label (HSS, 't', Current_Scope);
+      Process_End_Label
+        (Handled_Statement_Sequence (N), 't', Current_Scope);
       Update_Use_Clause_Chain;
       End_Scope;
 
@@ -5410,7 +5403,7 @@ package body Sem_Ch6 is
       --  the warning.
 
       declare
-         Stm : Node_Id := First (Statements (HSS));
+         Stm : Node_Id := First (Statements (Handled_Statement_Sequence (N)));
       begin
          --  Skip call markers installed by the ABE mechanism, labels, and
          --  Push_xxx_Error_Label to find the first real statement.