Add if-chain to switch conversion pass.

Add if-chain to switch conversion pass.

gcc/ChangeLog:

	PR tree-optimization/14799
	PR ipa/88702
	* Makefile.in: Add gimple-if-to-switch.o.
	* dbgcnt.def (DEBUG_COUNTER): Add new debug counter.
	* passes.def: Include new pass_if_to_switch pass.
	* timevar.def (TV_TREE_IF_TO_SWITCH): New timevar.
	* tree-pass.h (make_pass_if_to_switch): New.
	* tree-ssa-reassoc.c (struct operand_entry): Move to the header.
	(dump_range_entry): Move to header file.
	(debug_range_entry): Likewise.
	(no_side_effect_bb): Make it global.
	* tree-switch-conversion.h (simple_cluster::simple_cluster):
	Add inline for couple of functions in order to prevent error
	about multiple defined symbols.
	* gimple-if-to-switch.cc: New file.
	* tree-ssa-reassoc.h: New file.

gcc/testsuite/ChangeLog:

	PR tree-optimization/14799
	PR ipa/88702
	* gcc.dg/tree-ssa/pr96480.c: Disable if-to-switch conversion.
	* gcc.dg/tree-ssa/reassoc-32.c: Likewise.
	* g++.dg/tree-ssa/if-to-switch-1.C: New test.
	* gcc.dg/tree-ssa/if-to-switch-1.c: New test.
	* gcc.dg/tree-ssa/if-to-switch-2.c: New test.
	* gcc.dg/tree-ssa/if-to-switch-3.c: New test.
	* gcc.dg/tree-ssa/if-to-switch-4.c: New test.
	* gcc.dg/tree-ssa/if-to-switch-5.c: New test.
	* gcc.dg/tree-ssa/if-to-switch-6.c: New test.
	* gcc.dg/tree-ssa/if-to-switch-7.c: New test.
	* gcc.dg/tree-ssa/if-to-switch-8.c: New test.