phiopt: do factor_out_conditional_operation for all phis [PR112418]HEADtrunkmaster

Sometimes factor_out_conditional_operation can factor out
an operation that causes a phi node to become the same element.
Other times, we want to factor out a binary operator because
it can improve code generation, an example is PR 110015 (openjpeg).

Note this includes a heuristic to decide if factoring out the operation
is profitable or not. It can be expanded to include a better live range
extend detector. Right now it has a simple one where if it is live on a
dominating path, it is considered a live or if there are a small # of
assign statements (defaults to 5), then it does not extend the live range
too much.

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/112418

gcc/ChangeLog:

	* tree-ssa-phiopt.cc (is_factor_profitable): New function.
	(factor_out_conditional_operation): Add merge argument. Remove
	arg0/arg1 arguments. Return bool instead of the new phi.
	Early return for virtual ops. Call is_factor_profitable to
	check if the factoring would be profitable.
	(pass_phiopt::execute): Call factor_out_conditional_operation
	on all phis instead of just singleton phi.
	* doc/invoke.texi (--param phiopt-factor-max-stmts-live=): Document.
	* params.opt (--param=phiopt-factor-max-stmts-live=): New opt.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/factor_op_phi-1.c: New test.
	* gcc.dg/tree-ssa/factor_op_phi-2.c: New test.
	* gcc.dg/tree-ssa/factor_op_phi-3.c: New test.
	* gcc.dg/tree-ssa/factor_op_phi-4.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

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