[Ada] Fix crash on array component with nonstandard index type

[Eric Botcazou]

This is a regression present on mainline, 10 and 9 branches: the compiler goes 
into an infinite recursion eventually exhausting the stack for the declaration 
of a discriminated record type with an array component having a discriminant 
as bound and an index type that is an enumeration type with a non-standard 
representation clause.

Tested on x86_64-suse-linux, applied on the mainline, 10 and 9 branches.


2020-09-11  Eric Botcazou  <ebotca...@adacore.com>

        * gcc-interface/decl.c (gnat_to_gnu_entity) <E_Array_Subtype>: Only
        create extra subtypes for discriminants if the RM size of the base
        type of the index type is lower than that of the index type.


2020-09-11  Eric Botcazou  <ebotca...@adacore.com>

        * gnat.dg/specs/discr7.ads: New test.

-- 
Eric Botcazou
diff --git a/gcc/ada/gcc-interface/decl.c b/gcc/ada/gcc-interface/decl.c
index 8045fa5ff97..2b7392c62c0 100644
--- a/gcc/ada/gcc-interface/decl.c
+++ b/gcc/ada/gcc-interface/decl.c
@@ -2480,8 +2480,8 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 	      tree gnu_base_orig_max = TYPE_MAX_VALUE (gnu_base_index_type);
 	      tree gnu_min, gnu_max, gnu_high;
 
-	      /* We try to define subtypes for discriminants used as bounds
-		 that are more restrictive than those declared by using the
+	      /* We try to create subtypes for discriminants used as bounds
+		 that are more restrictive than those declared, by using the
 		 bounds of the index type of the base array type.  This will
 		 make it possible to calculate the maximum size of the record
 		 type more conservatively.  This may have already been done by
@@ -2489,8 +2489,8 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 		 there will be a conversion that needs to be removed first.  */
 	      if (CONTAINS_PLACEHOLDER_P (gnu_orig_min)
 		  && TYPE_RM_SIZE (gnu_base_index_type)
-		  && !tree_int_cst_lt (TYPE_RM_SIZE (gnu_index_type),
-				       TYPE_RM_SIZE (gnu_base_index_type)))
+		  && tree_int_cst_lt (TYPE_RM_SIZE (gnu_base_index_type),
+				      TYPE_RM_SIZE (gnu_index_type)))
 		{
 		  gnu_orig_min = remove_conversions (gnu_orig_min, false);
 		  TREE_TYPE (gnu_orig_min)
@@ -2501,8 +2501,8 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 
 	      if (CONTAINS_PLACEHOLDER_P (gnu_orig_max)
 		  && TYPE_RM_SIZE (gnu_base_index_type)
-		  && !tree_int_cst_lt (TYPE_RM_SIZE (gnu_index_type),
-				       TYPE_RM_SIZE (gnu_base_index_type)))
+		  && tree_int_cst_lt (TYPE_RM_SIZE (gnu_base_index_type),
+				      TYPE_RM_SIZE (gnu_index_type)))
 		{
 		  gnu_orig_max = remove_conversions (gnu_orig_max, false);
 		  TREE_TYPE (gnu_orig_max)

-- { dg-do compile }

package Discr7 is

  type Enum is (One, Two, Three);
  for Enum use (One => 1, Two => 2, Three => 3);

  type Arr is array (Integer range <>, Enum range <>) of Boolean;

  type Rec (D : Integer) is record
    A: Arr (1 .. D, Enum'Range);
  end record;

end Discr7;