[Ada] Implementation of simple storage pools for dynamic allocation

[Arnaud Charlet <charlet at adacore dot com>]

The pragma Simple_Storage_Pool is provided for designating a library-level
limited private or limited record type as a simple storage pool type.
This provides an alternative to Ada's standard Storage_Pools, where
the pool type is not required to be tagged or have associated finalization
actions, eliminating the need for run-time support. A simple storage pool type
is defined with an Allocate operation, and optionally can have Deallocate
and Storage_Size operations (as well as other user-defined operations).
An access type can be associated with a pool object by setting the
attribute (or aspect) Simple_Storage_Pool. Allocators for the type will
invoke the pool's Allocate procedure, and unchecked deallocation invokes
the Deallocate operation (if defined).

Tested on x86_64-pc-linux-gnu, committed on trunk

2012-02-08  Gary Dismukes  <dismukes@adacore.com>

	* aspects.ads (type Aspect_Id): Add Aspect_Simple_Storage_Pool.
	(Impl_Defined_Aspects): Add entry for Aspect_Simple_Storage_Pool.
	(Aspect_Argument): Add Name entry for Aspect_Simple_Storage_Pool.
	(Aspect_Names): Add entry for Aspect_Simple_Storage_Pool.
	* aspects.adb (Canonical_Aspect): Add entry for
	Aspect_Simple_Storage_Pool.
	* exp_attr.adb (Expand_N_Attribute_Reference): Handle case of
	Attribute_Simple_Storage_Pool in the same way as Storage_Pool
	(add conversion, analyze/resolve). For the Storage_Size attribute,
	for the simple pool case, locate and use the simple pool type's
	Storage_Size function (if any), otherwise evaluate to zero.
	* exp_ch4.adb (Expand_N_Allocator): In the case of an allocator
	for an access type with an associated simple storage pool,
	locate and use the pool type's Allocate.
	* exp_intr.adb (Expand_Unc_Deallocation): In the case where the
	access type has a simple storage pool, locate the pool type's
	Deallocate procedure (if present) and use it as the procedure
	to call on the Free operation.
	* freeze.adb (Freeze_Entity): In the case of a full type for
	a private type defined with pragma Simple_Storage_Pool, check
	that the full type is also appropriate for the pragma. For
	a simple storage pool type, validate that the operations
	Allocate, Deallocate (if present), and Storage_Size
	(if present) are defined with appropriate expected profiles.
	(Validate_Simple_Pool_Op_Formal): New procedure
	(Validate_Simple_Pool_Operation): New procedure Add with and
	use of Rtsfind.
	* par-prag.adb: Add Pragma_Simple_Storage_Pool to case statement
	(no action required).
	* sem_attr.adb (Analyze_Attribute): For the case of the
	Storage_Pool attribute, give a warning if the prefix type has an
	associated simple storage pool, and rewrite the attribute as a
	raise of Program_Error. In the case of the Simple_Storage_Pool
	attribute, check that the prefix type has an associated simple
	storage pool, and set the attribute type to the pool's type.
	* sem_ch13.adb (Analyze_Aspect_Specifications): Add
	Aspect_Simple_Storage_Pool case choice.
	(Analyze_Attribute_Definition_Clause): Add
	Aspect_Simple_Storage_Pool to case for Ignore_Rep_Clauses
	(no action). Add handling for Simple_Storage_Pool attribute
	definition, requiring the name to denote a simple storage pool
	object.
	(Check_Aspect_At_Freeze_Point): For a simple storage pool
	aspect, set the type to that of the name specified for the aspect.
	* sem_prag.adb (Analyze_Pragma): Add handling for pragma
	Simple_Storage_Pool, requiring that it applies to a library-level
	type declared in a package declaration that is a limited private
	or limited record type.
	* sem_res.adb (Resolve_Allocator): Flag an attempt to call a
	build-in-place function in an allocator for an access type with
	a simple storage pool as unsupported.
	* snames.ads-tmpl: Add Name_Simple_Storage_Pool.
	(type Attribute_Id): Add Attribute_Simple_Storage_Pool.
	(type Pragma_Id): Add Pragma_Simple_Storage_Pool.
	* snames.adb-tmpl (Get_Pragma_Id): Handle case of
	Name_Simple_Storage_Pool.
	(Is_Pragma_Name): Return True for Name_Simple_Storage_Pool.

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