This improves the infrastructure present in gigi to remove redundant checks, 
i.e. checks that can never fail at run time, in loops, either directly or by 
exposing more opportunities for the GIMPLE optimizers.  The patch is large but 
it also cleans up the GENERIC code generated by gigi, in particular removes a 
bunch of superfluous VIEW_CONVERT_EXPRs, so it's worth having IMO.

Tested on x86_64-suse-linux, applied on the mainline.


2015-11-18  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/ada-tree.h (DECL_INVARIANT_P): New macro.
	* gcc-interface/gigi.h (enum standard_datatypes): Remove
	ADT_longjmp_decl and add ADT_not_handled_by_others_decl.
	(longjmp_decl): Delete.
	(not_handled_by_others_decl): New macro.
	(build_simple_component_ref): Delete.
	(build_component_ref): Adjust prototype.
	* gcc-interface/decl.c (gnat_to_gnu_entity): Adjust calls to
	build_component_ref.
	(gnat_to_gnu_field): Set DECL_INVARIANT_P on discriminants
	without default value.
	* gcc-interface/trans.c (gigi): Reorder initialization sequence
	and add not_handled_by_others_decl.
	(Attribute_to_gnu): Adjust calls to build_component_ref.
	(Subprogram_Body_to_gnu): Likewise.
	(Call_to_gnu): Likewise.
	(Exception_Handler_to_gnu_sjlj): Likewise.
	(gnat_to_gnu): Likewise.
	(range_check_info_d): Add inserted_cond field.
	(Loop_Statement_to_gnu): Make two passes on the recorded range checks.
	(build_noreturn_cond): New static function.
	(Raise_Error_to_gnu): Record range checks in loops at -O1 and above.
	(make_invariant): New static function.
	(Loop_Statement_to_gnu): Use it to compute invariant expressions for
	the loop bounds if possible, but do not require it if loop unswitching
	is enabled.
	* gcc-interface/utils.c (convert_to_fat_pointer): Likewise.
	(convert): Likewise.
	(maybe_unconstrained_array): Likewise.  Call it instead of
	build_simple_component_ref and add guard for CONSTRUCTORs.
	(unchecked_convert): Likewise.
	* gcc-interface/utils2.c (compare_fat_pointers): Likewise.
	(build_simple_component_ref): Remove COMPONENT parameter, unify
	code dealing with VIEW_CONVERT_EXPR and make it more general,
	remove special treatment for CONSTRUCTORs of template types.
	(build_component_ref): Remove COMPONENT parameter and adjust call
	to build_simple_component_ref.
	(maybe_wrap_malloc): Likewise.
	(build_allocator): Likewise.
	(gnat_invariant_expr): Look through overflow checks, deal with
	addition and subtraction of constants and take into account
	DECL_INVARIANT_P for the COMPONENT_REF case.


2015-11-18  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/loop_optimization19.adb: New test.
	* gnat.dg/loop_optimization20.adb: Likewise.
	* gnat.dg/loop_optimization21.ad[sb]: Likewise.

-- 
Eric Botcazou