[COMMITTED] ada: Make Sem_Util.Is_Aliased_View predicate more robust

[COMMITTED] ada: Make Sem_Util.Is_Aliased_View predicate more robust

[Marc Poulhiès]

From: Eric Botcazou <ebotcazou@adacore.com>

The predicate implements the rules of the language so it needs to cope with
constructs rewritten by the expander, in particular explicit dereferences
that the expander uses liberally for various purposes.

This change makes the detection of rewritten calls more robust, plugging an
existing loophole for specific objects and exposing a missing propagation of
the Is_Aliased flag for certain build-in-place objects, as well as adds the
detection of rewritten return objects.

It also contains a small enhancement to Set_Debug_Info_Defining_Id aimed at
making it easier to debug the generated code by means of -gnatD.

gcc/ada/

	* sem_util.ads (Set_Debug_Info_Defining_Id): Adjust comment.
	* sem_util.adb (Is_Aliased_View) <N_Explicit_Dereference>: Return
	false for more artificial dereferences generated by the expander.
	(Set_Debug_Info_Defining_Id): Set Debug_Info_Needed unconditionally
	in -gnatD mode.
	* exp_ch6.adb (Replace_Renaming_Declaration_Id): Also preserve the
	Is_Aliased flag.

Tested on x86_64-pc-linux-gnu, committed on master.

---
 gcc/ada/exp_ch6.adb  |  4 ++++
 gcc/ada/sem_util.adb | 13 +++++++++++--
 gcc/ada/sem_util.ads |  4 ++--
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/gcc/ada/exp_ch6.adb b/gcc/ada/exp_ch6.adb
index 0bc2559751b..975a96668df 100644
--- a/gcc/ada/exp_ch6.adb
+++ b/gcc/ada/exp_ch6.adb
@@ -9378,6 +9378,10 @@ package body Exp_Ch6 is
       Preserve_Comes_From_Source (Orig_Id, Orig_Decl);
 
       Set_Comes_From_Source (New_Id, False);
+
+      --  Preserve aliased indication
+
+      Set_Is_Aliased (Orig_Id, Is_Aliased (New_Id));
    end Replace_Renaming_Declaration_Id;
 
    ---------------------------------
diff --git a/gcc/ada/sem_util.adb b/gcc/ada/sem_util.adb
index a1cebb08291..3132446515b 100644
--- a/gcc/ada/sem_util.adb
+++ b/gcc/ada/sem_util.adb
@@ -15255,8 +15255,15 @@ package body Sem_Util is
       then
          return Is_Aliased_View (Expression (Obj));
 
+      --  The dereference of an access-to-object value denotes an aliased view,
+      --  but this routine uses the rules of the language so we need to exclude
+      --  rewritten constructs that introduce artificial dereferences.
+
       elsif Nkind (Obj) = N_Explicit_Dereference then
-         return Nkind (Original_Node (Obj)) /= N_Function_Call;
+         return not Is_Captured_Function_Call (Obj)
+           and then not
+             (Nkind (Parent (Obj)) = N_Object_Renaming_Declaration
+               and then Is_Return_Object (Defining_Entity (Parent (Obj))));
 
       else
          return False;
@@ -27394,7 +27401,9 @@ package body Sem_Util is
 
    procedure Set_Debug_Info_Defining_Id (N : Node_Id) is
    begin
-      if Comes_From_Source (Defining_Identifier (N)) then
+      if Comes_From_Source (Defining_Identifier (N))
+        or else Debug_Generated_Code
+      then
          Set_Debug_Info_Needed (Defining_Identifier (N));
       end if;
    end Set_Debug_Info_Defining_Id;
diff --git a/gcc/ada/sem_util.ads b/gcc/ada/sem_util.ads
index b61695ea729..dc1bb084b54 100644
--- a/gcc/ada/sem_util.ads
+++ b/gcc/ada/sem_util.ads
@@ -3096,8 +3096,8 @@ package Sem_Util is
    --  associated name (i.e. the Node_Id associated with its name).
 
    procedure Set_Debug_Info_Defining_Id (N : Node_Id);
-   --  Call Set_Debug_Info_Needed on Defining_Identifier (N) if it comes
-   --  from source.
+   --  Call Set_Debug_Info_Needed on Defining_Identifier (N) if it comes from
+   --  source or we are in -gnatD mode, where we are debugging generated code.
 
    procedure Set_Debug_Info_Needed (T : Entity_Id);
    --  Sets the Debug_Info_Needed flag on entity T , and also on any entities
-- 
2.34.1