[Ada] Fold Enum_Rep attribute in evaluation and not in expansion

2020-06-10  Piotr Trojanek  <trojanek@adacore.com>

gcc/ada/

	* exp_attr.adb (Expand_N_Attribute_Reference): Remove folding
	for Enum_Rep attribute.
	* exp_spark.adb (Expand_SPARK_N_Attribute_Reference): Remove
	duplicated code for folding Enum_Rep attribute.
	* sem_attr.adb (Eval_Attribute): Relax condition for folding
	Enum_Rep attribute; previously dead code is now executed when
	the attribute prefix is an enumeration literal; refine type in
	processing of Enum_Val.

3 files changed, 9 insertions, 37 deletions

diff --git a/gcc/ada/exp_attr.adb b/gcc/ada/exp_attr.adb
index 67a18c6..356d3db 100644
--- a/gcc/ada/exp_attr.adb
+++ b/gcc/ada/exp_attr.adb
@@ -3159,17 +3159,8 @@ package body Exp_Attr is
             Expr := Pref;
          end if;
 
-         --  If the expression is an enumeration literal, it is replaced by the
-         --  literal value.
-
-         if Nkind (Expr) in N_Has_Entity
-           and then Ekind (Entity (Expr)) = E_Enumeration_Literal
-         then
-            Rewrite (N,
-              Make_Integer_Literal (Loc, Enumeration_Rep (Entity (Expr))));
-
-         --  If not constant-folded above, Enum_Type'Enum_Rep (X) or
-         --  X'Enum_Rep expands to
+         --  If not constant-folded, Enum_Type'Enum_Rep (X) or X'Enum_Rep
+         --  expands to
 
          --    target-type (X)
 
@@ -3185,7 +3176,7 @@ package body Exp_Attr is
          --  first convert to a small signed integer type in order not to lose
          --  the size information.
 
-         elsif Is_Enumeration_Type (Ptyp) then
+         if Is_Enumeration_Type (Ptyp) then
             Psiz := RM_Size (Base_Type (Ptyp));
 
             if Psiz < 8 then
diff --git a/gcc/ada/exp_spark.adb b/gcc/ada/exp_spark.adb
index c115a45..cab48f4 100644
--- a/gcc/ada/exp_spark.adb
+++ b/gcc/ada/exp_spark.adb
@@ -199,29 +199,6 @@ package body Exp_SPARK is
              Parameter_Associations => New_List (Expr)));
          Analyze_And_Resolve (N, Typ);
 
-      --  Whenever possible, replace a prefix which is an enumeration literal
-      --  by the corresponding literal value, just like it happens in the GNAT
-      --  expander.
-
-      elsif Attr_Id = Attribute_Enum_Rep then
-         declare
-            Exprs : constant List_Id := Expressions (N);
-         begin
-            if Is_Non_Empty_List (Exprs) then
-               Expr := First (Exprs);
-            else
-               Expr := Prefix (N);
-            end if;
-
-            --  If the argument is a literal, expand it
-
-            if Nkind (Expr) in N_Has_Entity
-              and then Ekind (Entity (Expr)) = E_Enumeration_Literal
-            then
-               Exp_Attr.Expand_N_Attribute_Reference (N);
-            end if;
-         end;
-
       elsif Attr_Id = Attribute_Object_Size
         or else Attr_Id = Attribute_Size
         or else Attr_Id = Attribute_Value_Size
diff --git a/gcc/ada/sem_attr.adb b/gcc/ada/sem_attr.adb
index e82082b..d2ac4c7 100644
--- a/gcc/ada/sem_attr.adb
+++ b/gcc/ada/sem_attr.adb
@@ -7719,7 +7719,11 @@ package body Sem_Attr is
       --  purpose, a string literal counts as an object (attributes of string
       --  literals can only appear in generated code).
 
-      if Is_Object_Reference (P) or else Nkind (P) = N_String_Literal then
+      if Is_Object_Reference (P)
+        or else Nkind (P) = N_String_Literal
+        or else (Is_Entity_Name (P)
+                 and then Ekind (Entity (P)) = E_Enumeration_Literal)
+      then
 
          --  For Component_Size, the prefix is an array object, and we apply
          --  the attribute to the type of the object. This is allowed for both
@@ -8533,7 +8537,7 @@ package body Sem_Attr is
       --------------
 
       when Attribute_Enum_Val => Enum_Val : declare
-         Lit : Node_Id;
+         Lit : Entity_Id;
 
       begin
          --  We have something like Enum_Type'Enum_Val (23), so search for a