re PR tree-optimization/90316 (large compile time increase in opt / alias stmt walking for Go example)

2019-05-13  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/90316
	* tree-ssa-pre.c (insert_aux): Fold into ...
	(insert): ... this function.  Use a RPO walk to reduce the
	number of required iterations.

From-SVN: r271124