Common API for accessing global and on-demand ranges.

Common API for accessing global and on-demand ranges.

This patch provides a generic API for accessing global ranges.  It is
meant to replace get_range_info() and get_ptr_nonnull() with one
common interface.  It uses the same API as the ranger (class
range_query), so there will now be one API for accessing local and
global ranges alike.

Follow-up patches will convert all users of get_range_info and
get_ptr_nonnull to this API.

For get_range_info, instead of:

  if (!POINTER_TYPE_P (TREE_TYPE (name)) && SSA_NAME_RANGE_INFO (name))
    get_range_info (name, vr);

You can now do:

  get_range_query (cfun)->range_of_expr (vr, name, [stmt]);

...as well as any other of the range_query methods (range_on_edge,
range_of_stmt, value_of_expr, value_on_edge, value_on_stmt, etc).

As per the API, range_of_expr will work on constants, SSA names, and
anything we support in irange::supports_type_p().

For pointers, the interface is the same, so instead of:

  else if (POINTER_TYPE_P (TREE_TYPE (name)) && SSA_NAME_PTR_INFO (name))
    {
      if (get_ptr_nonnull (name))
        stuff();
    }

One can do:

  get_range_query (cfun)->range_of_expr (vr, name, [stmt]);
  if (vr.nonzero_p ())
    stuff ();

Along with this interface, we are providing a mechanism by which a
pass can use an on-demand ranger transparently, without having to
change its code.  Of course, this assumes all get_range_info() and
get_ptr_nonnull() users have been converted to the new API, which
follow-up patches will do.

If a pass would prefer to use an on-demand ranger with finer grained
and context aware ranges, all it would have to do is call
enable_ranger() at the beginning of the pass, and disable_ranger() at
the end of the pass.

Note, that to use context aware ranges, any user of range_of_expr()
would need to pass additional context.  For example, the optional
gimple statement (or perhaps use range_on_edge or range_of_stmt).

The observant reader will note that get_range_query is tied to a
struct function, which may not be available in certain contexts, such
as at RTL time, gimple-fold, or some other places where we may or may
not have cfun set.

For cases where we are sure there is no function, you can use
get_global_range_query() instead of get_range_query(fun).  The API is
the same.

For cases where a function may be called with or without a function,
you could use the following idiom:

  range_query *query = cfun ? get_range_query (cfun)
    : get_global_range_query ();

  query->range_of_expr (range, expr, [stmt]);

The default range query obtained by get_range_query() is the global
range query, unless the user has enabled an on-demand ranger with
enable_ranger(), in which case it will use the currently active ranger.
That is, until disable_ranger() is called, at which point, we revert
back to global ranges.

We think this provides a generic way of accessing ranges, both
globally and locally, without having to keep track of types,
SSA_NAME_RANGE_INFO, and SSA_NAME_PTR_INFO.  We also hope this can be
used to transition passes from global to on-demand ranges when
appropriate.

gcc/ChangeLog:

	* function.c (allocate_struct_function): Set cfun->x_range_query.
	* function.h (struct function): Declare x_range_query.
	(get_range_query): New.
	(get_global_range_query): New.
	* gimple-range-cache.cc (ssa_global_cache::ssa_global_cache):
	Remove call to safe_grow_cleared.
	* gimple-range.cc (get_range_global): New.
	(gimple_range_global): Move from gimple-range.h.
	(get_global_range_query): New.
	(global_range_query::range_of_expr): New.
	(enable_ranger): New.
	(disable_ranger): New.
	* gimple-range.h (gimple_range_global): Move to gimple-range.cc.
	(class global_range_query): New.
	(enable_ranger): New.
	(disable_ranger): New.
	* gimple-ssa-evrp.c (evrp_folder::~evrp_folder): Rename
	dump_all_value_ranges to dump.
	* tree-vrp.c (vrp_prop::finalize): Same.
	* value-query.cc (range_query::dump): New.
	* value-query.h (range_query::dump): New.
	* vr-values.c (vr_values::dump_all_value_ranges): Rename to...
	(vr_values::dump): ...this.
	* vr-values.h (class vr_values): Rename dump_all_value_ranges to
	dump and make virtual.