[Ada] Fix leak of Do_Range_Check flag in -gnatVa mode

[Pierre-Marie de Rodat <derodat at adacore dot com>]

This fixes a small glitch in Insert_Valid_Check, which needs to
propagate the Do_Range_Check flag onto the rewritten expression, but
uses its Original_Node as the source of the copy.  Now Original_Node
does not necessarily point to the node that was just rewritten, but to
the ultimately original node, which is not the same node if the
expression was rewritten multiple times.  The end result is that a
stalled Do_Range_Check flag can be wrongly resintated and leak to the
code generator.

Tested on x86_64-pc-linux-gnu, committed on trunk

2019-08-12  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* checks.adb (Insert_Valid_Check): Do not retrieve the
	Do_Range_Check flag from the Original_Node but from the
	Validated_Object.  Remove useless bypass for floating-point
	types.

gcc/testsuite/

	* gnat.dg/range_check7.adb: New testcase.

--- gcc/ada/checks.adb
+++ gcc/ada/checks.adb
@@ -7589,17 +7589,14 @@ package body Checks is
 
             Set_Validated_Object (Var_Id, New_Copy_Tree (Exp));
 
-            --  Reset the Do_Range_Check flag so it doesn't leak elsewhere
-
-            Set_Do_Range_Check (Validated_Object (Var_Id), False);
-
             Rewrite (Exp, New_Occurrence_Of (Var_Id, Loc));
 
-            --  Copy the Do_Range_Check flag over to the new Exp, so it doesn't
-            --  get lost. Floating point types are handled elsewhere.
+            --  Move the Do_Range_Check flag over to the new Exp so it doesn't
+            --  get lost and doesn't leak elsewhere.
 
-            if not Is_Floating_Point_Type (Typ) then
-               Set_Do_Range_Check (Exp, Do_Range_Check (Original_Node (Exp)));
+            if Do_Range_Check (Validated_Object (Var_Id)) then
+               Set_Do_Range_Check (Exp);
+               Set_Do_Range_Check (Validated_Object (Var_Id), False);
             end if;
 
             PV := New_Occurrence_Of (Var_Id, Loc);

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/range_check7.adb
@@ -0,0 +1,22 @@
+--  { dg-do compile }
+--  { dg-options "-gnatVa" }
+
+procedure Range_Check7 is
+
+  type Short is range -32768 .. 32767;
+
+  type Int is range -2 ** 31 .. 2 ** 31 - 1;
+
+  subtype Nat is Int range 0 .. Int'Last;
+
+  type Ptr is access all Short;
+
+  procedure Proc (P : Ptr) is
+    N : constant Nat := Nat (P.all);
+  begin
+    null;
+  end;
+
+begin
+  null;
+end;