re PR tree-optimization/68157 (internal compiler error: in reassoc_stmt_dominates_stmt_p, at tree-ssa-reassoc.c:1287)

	PR tree-optimization/68157
	* tree-ssa-reassoc.c (attempt_builtin_powi): Set uid of
	pow_stmt or mul_stmt from stmt's uid.
	(reassociate_bb): Set uid of mul_stmt from stmt's uid.

	* g++.dg/opt/pr68157.C: New test.

From-SVN: r230530