optabs.c (shift_optab_p, [...]): New functions, split out from expand_binop.

optabs.c (shift_optab_p, [...]): New functions, split out from expand_binop.

gcc/
	* optabs.c (shift_optab_p, commutative_optab_p): New functions,
	split out from expand_binop.
	(avoid_expensive_constant): New function.
	(expand_binop_directly): Remove commutative_op argument and
	call cummutative_optab_p instead.  Do not change op0 or op1
	when swapping xop0 and xop1.  Apply avoid_expensive_constant
	to each argument after potential swapping.  Enforce the
	canonical order of commutative operands.
	(expand_binop): Use shift_optab_p and commutative_optab_p.
	Update the calls to expand_binop_directly.  Only force constants
	into registers when widening an operation.  Only swap operands
	once a direct expansion has been rejected.
	(expand_twoval_binop): Only force constants into registers when
	using a direct expansion.

From-SVN: r127991