[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, 2 insertions, 47 deletions

diff --git a/gcc/ada/sem_elab.adb b/gcc/ada/sem_elab.adb
index b8e3fb6..f912f8b 100644
--- a/gcc/ada/sem_elab.adb
+++ b/gcc/ada/sem_elab.adb
@@ -1809,11 +1809,6 @@ package body Sem_Elab is
       --  Determine whether arbitrary entity Id denotes a partial invariant
       --  procedure.
 
-      function Is_Postconditions_Proc (Id : Entity_Id) return Boolean;
-      pragma Inline (Is_Postconditions_Proc);
-      --  Determine whether arbitrary entity Id denotes internally generated
-      --  routine _Postconditions.
-
       function Is_Preelaborated_Unit (Id : Entity_Id) return Boolean;
       pragma Inline (Is_Preelaborated_Unit);
       --  Determine whether arbitrary entity Id denotes a unit which is subject
@@ -2481,14 +2476,6 @@ package body Sem_Elab is
          elsif Is_Partial_Invariant_Proc (Subp_Id) then
             null;
 
-         --  _Postconditions
-
-         elsif Is_Postconditions_Proc (Subp_Id) then
-            Output_Verification_Call
-              (Pred    => "postconditions",
-               Id      => Find_Enclosing_Scope (Call),
-               Id_Kind => "subprogram");
-
          --  Subprograms must come last because some of the previous cases fall
          --  under this category.
 
@@ -6638,14 +6625,6 @@ package body Sem_Elab is
             elsif Is_Partial_Invariant_Proc (Subp_Id) then
                null;
 
-            --  _Postconditions
-
-            elsif Is_Postconditions_Proc (Subp_Id) then
-               Info_Verification_Call
-                 (Pred    => "postconditions",
-                  Id      => Find_Enclosing_Scope (Call),
-                  Id_Kind => "subprogram");
-
             --  Subprograms must come last because some of the previous cases
             --  fall under this category.
 
@@ -13091,10 +13070,6 @@ package body Sem_Elab is
            (Extra : out Entity_Id;
             Kind  : out Invocation_Kind)
          is
-            Targ_Rep  : constant Target_Rep_Id :=
-                          Target_Representation_Of (Targ_Id, In_State);
-            Spec_Decl : constant Node_Id := Spec_Declaration (Targ_Rep);
-
          begin
             --  Accept within a task body
 
@@ -13180,12 +13155,6 @@ package body Sem_Elab is
                Extra := First_Formal_Type (Targ_Id);
                Kind  := Invariant_Verification;
 
-            --  Postcondition verification
-
-            elsif Is_Postconditions_Proc (Targ_Id) then
-               Extra := Find_Enclosing_Scope (Spec_Decl);
-               Kind  := Postcondition_Verification;
-
             --  Protected entry call
 
             elsif Is_Protected_Entry (Targ_Id) then
@@ -14454,8 +14423,7 @@ package body Sem_Elab is
            Is_Default_Initial_Condition_Proc (Id)
              or else Is_Initial_Condition_Proc (Id)
              or else Is_Invariant_Proc (Id)
-             or else Is_Partial_Invariant_Proc (Id)
-             or else Is_Postconditions_Proc (Id);
+             or else Is_Partial_Invariant_Proc (Id);
       end Is_Assertion_Pragma_Target;
 
       ----------------------------
@@ -14497,7 +14465,6 @@ package body Sem_Elab is
            Is_Accept_Alternative_Proc (Id)
              or else Is_Finalizer_Proc (Id)
              or else Is_Partial_Invariant_Proc (Id)
-             or else Is_Postconditions_Proc (Id)
              or else Is_TSS (Id, TSS_Deep_Adjust)
              or else Is_TSS (Id, TSS_Deep_Finalize)
              or else Is_TSS (Id, TSS_Deep_Initialize);
@@ -14653,18 +14620,6 @@ package body Sem_Elab is
              and then Is_Partial_Invariant_Procedure (Id);
       end Is_Partial_Invariant_Proc;
 
-      ----------------------------
-      -- Is_Postconditions_Proc --
-      ----------------------------
-
-      function Is_Postconditions_Proc (Id : Entity_Id) return Boolean is
-      begin
-         --  To qualify, the entity must denote a _Postconditions procedure
-
-         return
-           Ekind (Id) = E_Procedure and then Chars (Id) = Name_uPostconditions;
-      end Is_Postconditions_Proc;
-
       ---------------------------
       -- Is_Preelaborated_Unit --
       ---------------------------
@@ -17482,7 +17437,7 @@ package body Sem_Elab is
 
       if Nkind (N) = N_Procedure_Call_Statement
         and then Is_Entity_Name (Name (N))
-        and then Chars (Entity (Name (N))) = Name_uPostconditions
+        and then Chars (Entity (Name (N))) = Name_uWrapped_Statements
       then
          return;
       end if;