[Ada] Speed up enumeration'Value with perfect hash function

[Ada] Speed up enumeration'Value with perfect hash function

gcc/ada/

	* Makefile.rtl (GNATRTL_NONTASKING_OBJS): Add s-imagen, s-imen16,
	s-imen32, s-imenu8, s-pehage, s-valuen, s-vaen16, s-vaen32 and
	s-vaenu8.  Remove s-imenne, s-imgenu and s-valenu.
	* debug.adb (d_h): Document new usage.
	* einfo.ads (Lit_Hash): New attribute for enumeration types.
	(Set_Lit_Hash): Declare.
	* einfo.adb (Lit_Hash): New function.
	(Set_Lit_Hash): New procedure.
	(Write_Field21_Name): Print Lit_Hash for Enumeration_Kind.
	* exp_imgv.ads (Build_Enumeration_Image_Tables): Fix description
	and document the hash function and its tables.
	* exp_imgv.adb: Add with/use clauses for Debug.  Add with clause
	for System.Perfect_Hash_Generators.
	(Append_Table_To): New helper routine.
	(Build_Enumeration_Image_Tables): Call it to build the tables.
	In the main unit, register the literals with the hash generator.
	If they are sufficiently many and -gnatd_h is not passed, generate
	a perfect hash function and its tables; otherwise, generate a dummy
	hash function.  For the other units, generate only the declaration.
	In all cases, set Lit_Hash to the entity of the function, if any.
	(Expand_Value_Attribute): Pass the 'Unrestricted_Access of Lit_Hash,
	if any, as third argument to the Value_Enumeration_NN function.
	* gnat1drv.adb (Adjust_Global_Switches): force simpler implementation
	of 'Value in CodePeer_Mode.
	* lib.ads (Synchronize_Serial_Number): Add SN parameter.
	* lib.adb (Synchronize_Serial_Number): Assert that it is larger than
	the serial number of the current unit and set the latter to it only
	in this case.
	* rtsfind.ads (RTU_Id): Add System_Img_Enum_8, System_Img_Enum_16,
	System_Img_Enum_32, System_Val_Enum_8, System_Val_Enum_16 and
	System_Val_Enum_32.  Remove System_Img_Enum, System_Img_Enum_New
	and System_Val_Enum.
	* sem_attr.adb (Analyze_Access_Attribute): Do not flag a compiler
	generated Unrestricted_Access attribute as illegal in a declare
	expression.
	(RE_Unit_Table): Adjust to above changes.
	* libgnat/g-heasor.ads: Add pragma Compiler_Unit_Warning.
	* libgnat/g-table.ads: Likewise.
	* libgnat/g-pehage.ads: Add with clause and local renaming for
	System.Perfect_Hash_Generators.
	(Optimization): Turn into derived type.
	(Verbose): Turn into renaming.
	(Too_Many_Tries): Likewise.
	(Table_Name): Move to System.Perfect_Hash_Generators.
	(Define): Likewise.
	(Value): Likewise.
	* libgnat/g-pehage.adb: Remove with clause for Ada.Directories,
	GNAT.Heap_Sort_G and GNAT.Table.  Move bulk of implementation
	to System.Perfect_Hash_Generators, only keep the output part.
	* libgnat/s-imagen.ads: New generic unit.
	* libgnat/s-imagen.adb: New body.
	* libgnat/s-imen16.ads: New unit.
	* libgnat/s-imen32.ads: Likewise.
	* libgnat/s-imenu8.ads: Likewise.
	* libgnat/s-imenne.ads: Adjust description.
	* libgnat/s-imgenu.ads: Delete.
	* libgnat/s-imgenu.adb: Likewise.
	* libgnat/s-pehage.ads: New unit from GNAT.Perfect_Hash_Generators.
	* libgnat/s-pehage.adb: New body from GNAT.Perfect_Hash_Generators.
	* libgnat/s-valuen.ads: New generic unit.
	* libgnat/s-valuen.adb: New body.
	* libgnat/s-vaen16.ads: New unit.
	* libgnat/s-vaen32.ads: Likewise.
	* libgnat/s-vaenu8.ads: Likewise.
	* libgnat/s-valenu.ads: Delete.
	* libgnat/s-valenu.adb: Likewise.
	* gcc-interface/Make-lang.in (GNAT_ADA_OBJS): Add s-pehage.o.
	(GNATBIND_OBJS): Remove s-imgenu.o.