[COMMITTED 20/31] ada: Fix assembler error for gigantic library-level object on 64-bit Windows

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

From: Eric Botcazou <ebotcazou@adacore.com>

Most small 64-bit code models have a limit of 2 GB on the span of binaries,
so we also use the limit for the size of the largest statically allocatable
object by the compiler.  If the limit is topped, the compiler switches over
to a dynamic allocation (if not forbidden) after giving a warning.

gcc/ada/

	* gcc-interface/decl.cc (gnat_to_gnu_entity) <E_Variable>: Give a
	warning for a statically allocated object whose size is constant,
	valid but too large.
	(allocatable_size_p): In the static case, return false for a size
	that is constant, valid but too large.

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

---
 gcc/ada/gcc-interface/decl.cc | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/gcc/ada/gcc-interface/decl.cc b/gcc/ada/gcc-interface/decl.cc
index 41d5c29a17c..e16ee6edac5 100644
--- a/gcc/ada/gcc-interface/decl.cc
+++ b/gcc/ada/gcc-interface/decl.cc
@@ -1415,10 +1415,22 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 			     false);
 		  }
 
-		if (TREE_CODE (TYPE_SIZE_UNIT (gnu_alloc_type)) == INTEGER_CST
-		    && !valid_constant_size_p (TYPE_SIZE_UNIT (gnu_alloc_type)))
-		  post_error ("??Storage_Error will be raised at run time!",
-			      gnat_entity);
+		/* Give a warning if the size is constant but too large.  */
+		if (TREE_CODE (TYPE_SIZE_UNIT (gnu_alloc_type)) == INTEGER_CST)
+		  {
+		    if (valid_constant_size_p (TYPE_SIZE_UNIT (gnu_alloc_type)))
+		      {
+			post_error
+			  ("??too large object cannot be allocated statically",
+			   gnat_entity);
+			post_error ("\\?dynamic allocation will be used instead",
+				    gnat_entity);
+		      }
+
+		    else
+		      post_error ("??Storage_Error will be raised at run time!",
+				  gnat_entity);
+		  }
 
 		gnu_expr
 		  = build_allocator (gnu_alloc_type, gnu_expr, gnu_type,
@@ -6822,9 +6834,12 @@ constructor_address_p (tree gnu_expr)
 static bool
 allocatable_size_p (tree gnu_size, bool static_p)
 {
-  /* We can allocate a fixed size if it is a valid for the middle-end.  */
+  /* We can allocate a fixed size if it is a valid for the middle-end but, for
+     a static allocation, we do not allocate more than 2 GB because this would
+     very likely be unintended and problematic for usual code models.  */
   if (TREE_CODE (gnu_size) == INTEGER_CST)
-    return valid_constant_size_p (gnu_size);
+    return valid_constant_size_p (gnu_size)
+	   && (!static_p || tree_to_uhwi (gnu_size) <= INT_MAX);
 
   /* We can allocate a variable size if this isn't a static allocation.  */
   else
-- 
2.43.2