[COMMITTED] ada: Fix for validity checks combined with aliasing checks

["Marc Poulhiès" <poulhies@adacore.com>]

From: Justin Squirek <squirek@adacore.com>

Attribute Overlaps_Storage, which can appear implicitly in expansion of
aliasing checks, is now excluded from operand validity checks. Likewise
for attribute Has_Same_Storage.

gcc/ada/

	* exp_attr.adb (Expand_N_Attribute_Reference): Skip operand
	validity checks for attributes Has_Same_Storage and
	Overlaps_Storage.

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

---
 gcc/ada/exp_attr.adb | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/gcc/ada/exp_attr.adb b/gcc/ada/exp_attr.adb
index 3c3f725cf27..1ef30656496 100644
--- a/gcc/ada/exp_attr.adb
+++ b/gcc/ada/exp_attr.adb
@@ -1998,16 +1998,22 @@ package body Exp_Attr is
    --  Start of processing for Expand_N_Attribute_Reference
 
    begin
-      --  Do required validity checking, if enabled. Do not apply check to
-      --  output parameters of an Asm instruction, since the value of this
-      --  is not set till after the attribute has been elaborated, and do
-      --  not apply the check to the arguments of a 'Read or 'Input attribute
-      --  reference since the scalar argument is an OUT scalar.
+      --  Do required validity checking, if enabled.
+      --
+      --  Skip check for output parameters of an Asm instruction (since their
+      --  valuesare not set till after the attribute has been elaborated),
+      --  for the arguments of a 'Read or 'Input attribute reference (since
+      --  the scalar argument is an OUT scalar) and for the arguments of a
+      --  'Has_Same_Storage or 'Overlaps_Storage attribute reference (which not
+      --  considered to be reads of their prefixes and expressions, see Ada RM
+      --  13.3(73.10/3)).
 
       if Validity_Checks_On and then Validity_Check_Operands
         and then Id /= Attribute_Asm_Output
         and then Id /= Attribute_Read
         and then Id /= Attribute_Input
+        and then Id /= Attribute_Has_Same_Storage
+        and then Id /= Attribute_Overlaps_Storage
       then
          declare
             Expr : Node_Id;
-- 
2.34.1