re PR tree-optimization/40436 (0.5% code size regression caused by r147852)

re PR tree-optimization/40436 (0.5% code size regression caused by r147852)

	PR tree-optimization/40436
	* ipa-inline.c (leaf_node_p): Implement using is_inexpensive_builtin.
	* tree-inline.c (estimate_num_insns): Inexpensive builtins are like
	normal instructions; be sure bultin is not implemented in this file;
	compute non-zero return cost.
	(init_inline_once): Reduce builtin_call_cost to 1; set return cost.
	* tree-inline.h (eni_weights_d): Add return cost.

From-SVN: r166517