decl.c (gnat_to_gnu_field): Do not enforce strict alignment for simple volatile field...

	* gcc-interface/decl.c (gnat_to_gnu_field): Do not enforce strict
	alignment for simple volatile fields and remove associated errors.
testsuite/
	* gnat.dg/specs/volatile1.ads: Remove obsolete errors.
	* gnat.dg/specs/clause_on_volatile.ads: Likewise.

From-SVN: r248320

diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index 1c12460f11117b55c3750a4bd2d3ebec1041124d..e7d5692a286cb0e242d9f9d5fde1c8eba6f19e34 100644 (file)
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,8 @@
+2017-05-22  Eric Botcazou  <ebotcazou@adacore.com>
+
+       * gcc-interface/decl.c (gnat_to_gnu_field): Do not enforce strict
+       alignment for simple volatile fields and remove associated errors.
+
 2017-05-15  Eric Botcazou  <ebotcazou@adacore.com>
 
        * gcc-interface/gigi.h (get_elaboration_procedure): Delete.

diff --git a/gcc/ada/gcc-interface/decl.c b/gcc/ada/gcc-interface/decl.c
index dee59c0324cdd6a91a6a69ecf4ea296e187a4566..4bf14649d97459ac89e6738a9caf3267b2309fad 100644 (file)
--- a/gcc/ada/gcc-interface/decl.c
+++ b/gcc/ada/gcc-interface/decl.c
@@ -6783,19 +6783,24 @@ gnat_to_gnu_field (Entity_Id gnat_field, tree gnu_record_type, int packed,
 {
   const Entity_Id gnat_record_type = Underlying_Type (Scope (gnat_field));
   const Entity_Id gnat_field_type = Etype (gnat_field);
-  const bool is_aliased
-    = Is_Aliased (gnat_field);
   const bool is_atomic
     = (Is_Atomic_Or_VFA (gnat_field) || Is_Atomic_Or_VFA (gnat_field_type));
+  const bool is_aliased = Is_Aliased (gnat_field);
   const bool is_independent
     = (Is_Independent (gnat_field) || Is_Independent (gnat_field_type));
   const bool is_volatile
     = (Treat_As_Volatile (gnat_field) || Treat_As_Volatile (gnat_field_type));
+  const bool is_strict_alignment = Strict_Alignment (gnat_field_type);
+  /* We used to consider that volatile fields also require strict alignment,
+     but that was an interpolation and would cause us to reject a pragma
+     volatile on a packed record type containing boolean components, while
+     there is no basis to do so in the RM.  In such cases, the writes will
+     involve load-modify-store sequences, but that's OK for volatile.  The
+     only constraint is the implementation advice whereby only the bits of
+     the components should be accessed if they both start and end on byte
+     boundaries, but that should be guaranteed by the GCC memory model.  */
   const bool needs_strict_alignment
-    = (is_aliased
-       || is_independent
-       || is_volatile
-       || Strict_Alignment (gnat_field_type));
+    = (is_atomic || is_aliased || is_independent || is_strict_alignment);
   tree gnu_field_type = gnat_to_gnu_type (gnat_field_type);
   tree gnu_field_id = get_entity_name (gnat_field);
   tree gnu_field, gnu_size, gnu_pos;
@@ -6917,9 +6922,7 @@ gnat_to_gnu_field (Entity_Id gnat_field, tree gnu_record_type, int packed,
                s = "position of aliased field& must be multiple of ^ bits";
              else if (is_independent)
                s = "position of independent field& must be multiple of ^ bits";
-             else if (is_volatile)
-               s = "position of volatile field& must be multiple of ^ bits";
-             else if (Strict_Alignment (gnat_field_type))
+             else if (is_strict_alignment)
                s = "position of & with aliased or tagged part must be"
                    " multiple of ^ bits";
              else
@@ -6947,9 +6950,7 @@ gnat_to_gnu_field (Entity_Id gnat_field, tree gnu_record_type, int packed,
                    s = "size of aliased field& must be ^ bits";
                  else if (is_independent)
                    s = "size of independent field& must be at least ^ bits";
-                 else if (is_volatile)
-                   s = "size of volatile field& must be at least ^ bits";
-                 else if (Strict_Alignment (gnat_field_type))
+                 else if (is_strict_alignment)
                    s = "size of & with aliased or tagged part must be"
                        " at least ^ bits";
                  else
@@ -6969,10 +6970,7 @@ gnat_to_gnu_field (Entity_Id gnat_field, tree gnu_record_type, int packed,
                  if (is_independent)
                    s = "size of independent field& must be multiple of"
                        " Storage_Unit";
-                 else if (is_volatile)
-                   s = "size of volatile field& must be multiple of"
-                       " Storage_Unit";
-                 else if (Strict_Alignment (gnat_field_type))
+                 else if (is_strict_alignment)
                    s = "size of & with aliased or tagged part must be"
                        " multiple of Storage_Unit";
                  else
@@ -7079,9 +7077,9 @@ gnat_to_gnu_field (Entity_Id gnat_field, tree gnu_record_type, int packed,
   /* Now create the decl for the field.  */
   gnu_field
     = create_field_decl (gnu_field_id, gnu_field_type, gnu_record_type,
-                        gnu_size, gnu_pos, packed, Is_Aliased (gnat_field));
+                        gnu_size, gnu_pos, packed, is_aliased);
   Sloc_to_locus (Sloc (gnat_field), &DECL_SOURCE_LOCATION (gnu_field));
-  DECL_ALIASED_P (gnu_field) = Is_Aliased (gnat_field);
+  DECL_ALIASED_P (gnu_field) = is_aliased;
   TREE_SIDE_EFFECTS (gnu_field) = TREE_THIS_VOLATILE (gnu_field) = is_volatile;
 
   if (Ekind (gnat_field) == E_Discriminant)

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 0ae3270e1c04b2611325e5bfbf69a268ca0be6a7..575ed96c46a1f572557314ed83676f155054ae21 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-05-22  Eric Botcazou  <ebotcazou@adacore.com>
+
+       * gnat.dg/specs/volatile1.ads: Remove obsolete errors.
+       * gnat.dg/specs/clause_on_volatile.ads: Likewise.
+
 2017-05-21  Paolo Carlini  <paolo.carlini@oracle.com>
 
        PR c++/70265

diff --git a/gcc/testsuite/gnat.dg/specs/clause_on_volatile.ads b/gcc/testsuite/gnat.dg/specs/clause_on_volatile.ads
index 68799a757a2b48f69d2440474052f420fb49abe9..f4c0b985b54f8da3331a8bc4f730544a225c70a5 100644 (file)
--- a/gcc/testsuite/gnat.dg/specs/clause_on_volatile.ads
+++ b/gcc/testsuite/gnat.dg/specs/clause_on_volatile.ads
@@ -57,7 +57,7 @@ package Clause_On_Volatile is
   end record;
   For V1'Alignment use 4;
   for V1 use record
-     VW at 0 range 0 .. 15; -- { dg-error "must be at least" }
+     VW at 0 range 0 .. 15;
   end record;
 
   type V2 is record
@@ -67,7 +67,7 @@ package Clause_On_Volatile is
   For V2'Alignment use 4;
   for V2 use record
      B at 0 range 0 .. 7;
-     VW at 1 range 0 .. 31; -- { dg-error "must be multiple" }
+     VW at 1 range 0 .. 31;
   end record;
 
   type V3 is record
@@ -77,7 +77,7 @@ package Clause_On_Volatile is
   For V3'Alignment use 4;
   for V3 use record
      B at 0 range 0 .. 7;
-     VW at 1 range 0 .. 15; -- { dg-error "must be (multiple|at least)" }
+     VW at 1 range 0 .. 15;
   end record;
 
 end Clause_On_Volatile;

diff --git a/gcc/testsuite/gnat.dg/specs/volatile1.ads b/gcc/testsuite/gnat.dg/specs/volatile1.ads
index 40ad4806e479710c9c90f52d0b5176dce2ec52e7..6f9421af45f18233a254a775b3c5e013f754c3f3 100644 (file)
--- a/gcc/testsuite/gnat.dg/specs/volatile1.ads
+++ b/gcc/testsuite/gnat.dg/specs/volatile1.ads
@@ -19,7 +19,7 @@ package Volatile1 is
     pragma Volatile (C);
   end record;
   for R2 use record
-    C at 0 range 0 .. 10; -- { dg-error "size of volatile field" }
+    C at 0 range 0 .. 10;
   end record;
 
 end Volatile1;