[Ada] Handle secondary stack memory allocations alignment

To accomodate cases where objects allocated on the secondary stack
needed a more constrained alignement than Standard'Maximum_Alignement,
the alignment for all allocations in the full runtime were forced on to
be aligned on Standard'Maximum_Alignement*2. This changes removes this
workaround and correctly handles the over-alignment in all runtimes.

This change modifies the SS_Allocate procedure to accept a new Alignment
parameter and to dynamically realign the pointer returned by the memory
allocation (Allocate_* functions or dedicated stack allocations for
zfp/cert).

It also simplifies the 0-sized allocations by not allocating any memory
if pointer is already correctly aligned (already the case in cert and
zfp runtimes).

gcc/ada/

	* libgnat/s-secsta.ads (SS_Allocate): Add new Alignment
	parameter.
	(Memory_Alignment): Remove.
	* libgnat/s-secsta.adb (Align_Addr): New.
	(SS_Allocate): Add new Alignment parameter. Realign pointer if
	needed. Don't allocate anything for 0-sized allocations.
	* gcc-interface/utils2.cc (build_call_alloc_dealloc_proc): Add
	allocated object's alignment as last parameter to allocation
	invocation.

1 files changed, 6 insertions, 4 deletions

diff --git a/gcc/ada/gcc-interface/utils2.cc b/gcc/ada/gcc-interface/utils2.cc
index ae81a0d..0dcc9ff 100644
--- a/gcc/ada/gcc-interface/utils2.cc
+++ b/gcc/ada/gcc-interface/utils2.cc
@@ -2139,6 +2139,8 @@ build_call_alloc_dealloc_proc (tree gnu_obj, tree gnu_size, tree gnu_type,
 			       Entity_Id gnat_proc, Entity_Id gnat_pool)
 {
   tree gnu_proc = gnat_to_gnu (gnat_proc);
+  tree gnu_align = size_int (TYPE_ALIGN (gnu_type) / BITS_PER_UNIT);
+
   tree gnu_call;
 
   /* A storage pool's underlying type is a record type for both predefined
@@ -2154,7 +2156,6 @@ build_call_alloc_dealloc_proc (tree gnu_obj, tree gnu_size, tree gnu_type,
 
       tree gnu_pool = gnat_to_gnu (gnat_pool);
       tree gnu_pool_addr = build_unary_op (ADDR_EXPR, NULL_TREE, gnu_pool);
-      tree gnu_align = size_int (TYPE_ALIGN (gnu_type) / BITS_PER_UNIT);
 
       gnu_size = convert (gnu_size_type, gnu_size);
       gnu_align = convert (gnu_size_type, gnu_align);
@@ -2178,6 +2179,7 @@ build_call_alloc_dealloc_proc (tree gnu_obj, tree gnu_size, tree gnu_type,
       tree gnu_size_type = gnat_to_gnu_type (gnat_size_type);
 
       gnu_size = convert (gnu_size_type, gnu_size);
+      gnu_align = convert (gnu_size_type, gnu_align);
 
       if (DECL_BUILT_IN_CLASS (gnu_proc) == BUILT_IN_FRONTEND
 	  && DECL_FE_FUNCTION_CODE (gnu_proc) == BUILT_IN_RETURN_SLOT)
@@ -2191,7 +2193,7 @@ build_call_alloc_dealloc_proc (tree gnu_obj, tree gnu_size, tree gnu_type,
 
 	  gnu_call = DECL_RESULT (current_function_decl);
 
-	  /* The allocation has alreay been done by the caller so we check that
+	  /* The allocation has already been done by the caller so we check that
 	     we are not going to overflow the return slot.  */
 	  if (TYPE_CI_CO_LIST (TREE_TYPE (current_function_decl)))
 	    gnu_ret_size
@@ -2216,7 +2218,7 @@ build_call_alloc_dealloc_proc (tree gnu_obj, tree gnu_size, tree gnu_type,
 	gnu_call = build_call_n_expr (gnu_proc, 2, gnu_obj, gnu_size);
 
       else
-	gnu_call = build_call_n_expr (gnu_proc, 1, gnu_size);
+	gnu_call = build_call_n_expr (gnu_proc, 2, gnu_size, gnu_align);
     }
 
   return gnu_call;
@@ -2334,7 +2336,7 @@ maybe_wrap_free (tree data_ptr, tree data_type)
 
 /* Build a GCC tree to call an allocation or deallocation function.
    If GNU_OBJ is nonzero, it is an object to deallocate.  Otherwise,
-   generate an allocator.
+   generate an allocation.
 
    GNU_SIZE is the number of bytes to allocate and GNU_TYPE is the contained
    object type, used to determine the to-be-honored address alignment.