[gcc r11-3493] Fix bogus alignment warning on address clause

[gcc r11-3493] Fix bogus alignment warning on address clause

[Eric Botcazou]

https://gcc.gnu.org/g:88795e14ae7143bd8039af68d2d876ae34568799

commit r11-3493-g88795e14ae7143bd8039af68d2d876ae34568799
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Mon Sep 28 09:00:46 2020 +0200

    Fix bogus alignment warning on address clause
    
    The compiler gives a bogus alignment warning on an address clause and
    a discriminated record type with variable size.
    
    gcc/ada/ChangeLog:
            * gcc-interface/decl.c (maybe_saturate_size): Add ALIGN parameter
            and round down the result to ALIGN.
            (gnat_to_gnu_entity): Adjust calls to maybe_saturate_size.
    
    gcc/testsuite/ChangeLog:
            * gnat.dg/addr16.adb: New test.
            * gnat.dg/addr16_pkg.ads: New helper.

Diff:
---
 gcc/ada/gcc-interface/decl.c         | 28 ++++++++++++++++++++--------
 gcc/testsuite/gnat.dg/addr16.adb     | 14 ++++++++++++++
 gcc/testsuite/gnat.dg/addr16_pkg.ads |  9 +++++++++
 3 files changed, 43 insertions(+), 8 deletions(-)

diff --git a/gcc/ada/gcc-interface/decl.c b/gcc/ada/gcc-interface/decl.c
index c9c2a95170f..cd0a50b2083 100644
--- a/gcc/ada/gcc-interface/decl.c
+++ b/gcc/ada/gcc-interface/decl.c
@@ -232,7 +232,7 @@ static tree build_position_list (tree, bool, tree, tree, unsigned int, tree);
 static vec<subst_pair> build_subst_list (Entity_Id, Entity_Id, bool);
 static vec<variant_desc> build_variant_list (tree, Node_Id, vec<subst_pair>,
 					     vec<variant_desc>);
-static tree maybe_saturate_size (tree);
+static tree maybe_saturate_size (tree, unsigned int align);
 static tree validate_size (Uint, tree, Entity_Id, enum tree_code, bool, bool,
 			   const char *, const char *);
 static void set_rm_size (Uint, tree, Entity_Id);
@@ -4425,7 +4425,12 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 	  /* If the size is self-referential, annotate the maximum value
 	     after saturating it, if need be, to avoid a No_Uint value.  */
 	  if (CONTAINS_PLACEHOLDER_P (gnu_size))
-	    gnu_size = maybe_saturate_size (max_size (gnu_size, true));
+	    {
+	      const unsigned int align
+		= UI_To_Int (Alignment (gnat_entity)) * BITS_PER_UNIT;
+	      gnu_size
+		= maybe_saturate_size (max_size (gnu_size, true), align);
+	    }
 
 	  /* If we are just annotating types and the type is tagged, the tag
 	     and the parent components are not generated by the front-end so
@@ -4461,7 +4466,8 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 		  gnu_size = size_binop (PLUS_EXPR, gnu_size, offset);
 		}
 
-	      gnu_size = maybe_saturate_size (round_up (gnu_size, align));
+	      gnu_size
+		= maybe_saturate_size (round_up (gnu_size, align), align);
 	      Set_Esize (gnat_entity, annotate_value (gnu_size));
 
 	      /* Tagged types are Strict_Alignment so RM_Size = Esize.  */
@@ -8946,15 +8952,21 @@ build_variant_list (tree gnu_qual_union_type, Node_Id gnat_variant_part,
 }
 \f
 /* If SIZE has overflowed, return the maximum valid size, which is the upper
-   bound of the signed sizetype in bits; otherwise return SIZE unmodified.  */
+   bound of the signed sizetype in bits, rounded down to ALIGN.  Otherwise
+   return SIZE unmodified.  */
 
 static tree
-maybe_saturate_size (tree size)
+maybe_saturate_size (tree size, unsigned int align)
 {
   if (TREE_CODE (size) == INTEGER_CST && TREE_OVERFLOW (size))
-    size = size_binop (MULT_EXPR,
-		       fold_convert (bitsizetype, TYPE_MAX_VALUE (ssizetype)),
-		       build_int_cst (bitsizetype, BITS_PER_UNIT));
+    {
+      size
+	= size_binop (MULT_EXPR,
+		      fold_convert (bitsizetype, TYPE_MAX_VALUE (ssizetype)),
+		      build_int_cst (bitsizetype, BITS_PER_UNIT));
+      size = round_down (size, align);
+    }
+
   return size;
 }
 
diff --git a/gcc/testsuite/gnat.dg/addr16.adb b/gcc/testsuite/gnat.dg/addr16.adb
new file mode 100644
index 00000000000..8f09da023fb
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/addr16.adb
@@ -0,0 +1,14 @@
+-- { dg-do compile }
+
+with Addr16_Pkg; use Addr16_Pkg;
+
+procedure Addr16 (R : Rec) is
+
+  pragma Unsuppress (Alignment_Check);
+
+  B : Integer;
+  for B'Address use R.A'Address;
+
+begin
+  null;
+end;
diff --git a/gcc/testsuite/gnat.dg/addr16_pkg.ads b/gcc/testsuite/gnat.dg/addr16_pkg.ads
new file mode 100644
index 00000000000..9a1b9e3b21b
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/addr16_pkg.ads
@@ -0,0 +1,9 @@
+package Addr16_Pkg is
+
+  type Arr is array (Positive range <>) of Long_Long_Integer;
+
+  type Rec (D : Positive) is record
+    A : Arr (1 .. D);
+  end record;
+
+end Addr16_Pkg;