tree-scalar-evolution.c (follow_ssa_edge_in_rhs, [...]): Keep more precise track of the size of the expression.

	* tree-scalar-evolution.c (follow_ssa_edge_in_rhs,
	follow_ssa_edge_in_condition_phi, follow_ssa_edge): Keep more precise
	track of the size of the expression.
	* cfghooks.c (merge_blocks): Remove block from loops structure only
	after call of the merge_blocks hook.

	* gcc.dg/tree-ssa/loop-28.c: New testcase.

From-SVN: r125595